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Rumors => Third Party Manufacturers => Topic started by: Canon Rumors on April 18, 2013, 08:54:44 AM

Title: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Canon Rumors on April 18, 2013, 08:54:44 AM
RONKONKOMA, NY, Apr. 18, 2013 — Sigma Corporation of America ([url=http://www.sigmaphoto.com]www.sigmaphoto.com[/url]), a leading researcher, developer, manufacturer and service provider for some of the world’s most impressive lines of lenses, cameras and flashes, today announced the Sigma 18-35mm F1.8 DC HSM Art lens, the market’s first zoom lens to achieve a maximum aperture F1.8 throughout the entire zoom range.

This revolutionary, wide aperture, standard zoom lens is created for DSLR cameras with APS-C size sensors, which translates to a focal range of 27-52.5mm on a 35mm camera. With a minimum focusing distance of 11 inches, and a maximum magnification ratio of 1:4.3, the 18-35mm is ideal for landscapes, portraits, still-life, studio, close-up and casual photography.

“Exceptionally fast apertures were previously unavailable in zoom lenses, so photographers turned to several prime lenses in a session to get bright images at various focal lengths. We’re incredibly excited to be the first manufacturer to bring the F1.8 standard zoom to the market and to provide photographers with a new level of creativity and convenience, with the outstanding image quality at the core of the new Sigma Global Vision,” said Mark Amir-Hamzeh, president of Sigma Corporation of America.

Amir-Hamzeh added that because developing a large aperture wide angle zoom lens can prove to be technologically and optically challenging, often resulting in various distortions, aberrations and field curvature, Sigma has tapped into its long history as a lens pioneer to overcome those issues in this new generation lens.

“Our experience with the wide angle designs of our 12-24mm F4.5-5.6 II DG HSM and our 8-16mm F4.5-5.6 DC HSM, and our research and development in our Aizu factory have prepared us for this technological advancement,” he said. “Our wide, glass-molded aspherical lens and the incorporation of Special Low Dispersion (SLD) glass have optimized power distribution of the optical elements and compensated for various aberrations, as well as curvature of field at the widest angle. We’re extremely proud of this achievement.”

The 18-35mm is the latest addition to the company’s company’s Art line of lenses, designed under the new Global Vision. The Global Vision lenses have a sleek new design with the manufacturing year stamped on the barrel, and are categorized by use into one of three groups: Art, Contemporary and Sports. The Art category delivers high-level artistic expression through sophisticated and abundant expressive power.

The new 18-35mm lens incorporates Sigma’s improved AF/MF switch and the use of Thermally Stable Composite (TSC) compound material, which has a high affinity to metal parts, consistently performs well at extreme temperatures, and reduces the size and weight of the lens. It is also compatible with Sigma’s new USB Dock, which will be available in coming months, enabling photographers to update lens firmware and adjust focus parameters from their computers.

Convenient handling is achieved with internal focusing and zooming, which prevents changes to the size of the lens. Additionally, the front part of the lens does not rotate, so special filters like circular polarizers can be used.

The 18-35mm lens’ Super Multi-Layer Coating reduces flare and ghosting and provides sharp and high contrast images, even in backlit conditions. The petal-type hood that is supplied with the lens will provide extra protection from flare and ghosting. Sigma’s Hyper Sonic Motor (HSM) ensures a silent, high-speed AF function and the optimized auto focus algorithm results in smooth focusing and full-time manual focusing capability. Lastly, the nine-blade, rounded diaphragm creates an attractive, round bokeh at large-aperture settings.

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: dswatson83 on April 18, 2013, 09:00:48 AM
I can just imagine Canon & Nikon engineers staring at their screens in disbelief. Sigma engineers have managed to crack some code to lens making. I have the Sigma 35mm f/1.4, just tested the new Sigma 30mm f/1.4 and can't wait for this. Amazing lenses Sigma, now please give me a nice 50mm lens because I am not at all happy with my Canon 50mm. At least my Canon 85mm is great.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Lee Jay on April 18, 2013, 09:06:26 AM
18mm?  What the heck is it with these idiotic lens makers.  We've got the 17-55, 18-55, 18-135, 18-200, 18-270 and now 18-35.  What do we have that starts at 24mm-equivalent?  The only one I own - the 15-85IS.

f/1.8 sounds interesting, but not if it starts at 18mm!!!

Pass.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: DzPhotography on April 18, 2013, 09:10:51 AM
Sounds interesting to me, but am I the only one worried about the price?  ???
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: dmills on April 18, 2013, 09:25:09 AM
Wow, a fast, wide zoom. I may be interested in a 7d2 afterall...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: killswitch on April 18, 2013, 09:32:05 AM
Sigma's art line series really kicking it up a notch with every release. Hope it performs well.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TWI by Dustin Abbott on April 18, 2013, 09:36:36 AM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: bseitz234 on April 18, 2013, 09:42:09 AM
18mm?  What the heck is it with these idiotic lens makers.  We've got the 17-55, 18-55, 18-135, 18-200, 18-270 and now 18-35.  What do we have that starts at 24mm-equivalent?  The only one I own - the 15-85IS.

f/1.8 sounds interesting, but not if it starts at 18mm!!!

Pass.

Well clearly they sell plenty of 17- and 18-something zooms, so I don't know if I'd go so far as to call them idiotic... it seems to be working. For most people the extra 3.2 or 4.8 mm don't seem to be make-or-break, and if they're that big a deal, they probably have a 10-something to get even wider...

I for one, am excited to see what this lens can do optically, and what Canon and/or Nikon might do in response. Suddenly a 2.8 zoom isn't as fast as it gets, and if they can do it in an 18-35 (much wider than "normal"), I'd be really curious to see what a 50-100 might look like for indoor sports. (doesn't have to go wide-tele, just normal-tele, still only 2x zoom, but could be very useful). Even if this came in at $1000, with similar optics, I'd consider giving up the extra 20mm of my 17-55 to get the extra stop-and-a-third of light from this lens.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TrumpetPower! on April 18, 2013, 09:49:07 AM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

Actually, the equivalent 135 format wouldn't need to be f/1.8. Remember that the crop format means greater depth of field and more noise, so add about a stop and a half to that f/1.8...and you're right at about the equivalent of the familiar f/2.8 of standard fast zooms for 135 format.

Don't get me worng; it's great to see fast glass coming to APS-C, and it's great to see Sigma throwing mud in the big boys's eyes. But "all" they've done is give APS-C some glass as fast (for the format) as what 135 has had for ages. It's high past somebody did this, but it's high past time precisely because it's no more remarkable than an f/2.8 zoom for 135 format.

Now, an f/1.8 zoom for 135, or an f/1.0 zoom for APS-C...that would be something truly remarkable....

Cheers,

b&
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: shutterlag on April 18, 2013, 09:56:25 AM
18mm?  What the heck is it with these idiotic lens makers.  We've got the 17-55, 18-55, 18-135, 18-200, 18-270 and now 18-35.  What do we have that starts at 24mm-equivalent?  The only one I own - the 15-85IS.

f/1.8 sounds interesting, but not if it starts at 18mm!!!

Pass.

First of all, this is the dumbest gripe I've read in a while.  If you're that unhappy, get a FF with a 24-70 and stop whining. 

Second, it's not even a valid gripe, as Tokina has a 16-28mm constant F2.8 that gets excellent reviews on crop.  Are you really that concerned about the difference between 25.6 and 24?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: preppyak on April 18, 2013, 10:01:41 AM
Don't get me worng; it's great to see fast glass coming to APS-C, and it's great to see Sigma throwing mud in the big boys's eyes. But "all" they've done is give APS-C some glass as fast (for the format) as what 135 has had for ages. It's high past somebody did this, but it's high past time precisely because it's no more remarkable than an f/2.8 zoom for 135 format.

Now, an f/1.8 zoom for 135, or an f/1.0 zoom for APS-C...that would be something truly remarkable.
And insanely heavy, expensive, etc. I'm only aware of Sigma's 20mm f/1.8 as something that fast, that wide, and it has an 82mm filter. It's also not a good lens. Obviously 24mm f/1.4 is doable by several companies. Perhaps a 24-70 f/1.8 zoom would be doable for full-frame, but, I can only imagine the weight and price.

That said, should be much easier for APS-C; I'm hoping the results are good, because I'd definitely buy one
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Lee Jay on April 18, 2013, 10:08:48 AM
18mm?  What the heck is it with these idiotic lens makers.  We've got the 17-55, 18-55, 18-135, 18-200, 18-270 and now 18-35.  What do we have that starts at 24mm-equivalent?  The only one I own - the 15-85IS.

f/1.8 sounds interesting, but not if it starts at 18mm!!!

Pass.

First of all, this is the dumbest gripe I've read in a while.  If you're that unhappy, get a FF with a 24-70 and stop whining. 

I have a 24-105.

Quote
Second, it's not even a valid gripe, as Tokina has a 16-28mm constant F2.8 that gets excellent reviews on crop.  Are you really that concerned about the difference between 25.6 and 24?

Yes, I am.

My point is, in the film days, only the cheapest kit zooms started at 28, and all the rest started at 24.  The same is true now of full-frame lenses (24-70, 24-105 versus 28-135).  But on crop, even the expensive lenses start at 27 or 28.  I won't buy one, and it's a stupid limitation.  The 17-55 could easily have been a 15-50.  The 18-35 could have been a 15-30.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: preppyak on April 18, 2013, 10:15:56 AM
First of all, this is the dumbest gripe I've read in a while.  If you're that unhappy, get a FF with a 24-70 and stop whining. 

Second, it's not even a valid gripe, as Tokina has a 16-28mm constant F2.8 that gets excellent reviews on crop.  Are you really that concerned about the difference between 25.6 and 24?
Yeah, especially since this zoom would do things a 15-85 can't touch; it'd be reasonable to own both as they would be for very different situations.

And since I can't imagine it'd be that great for night photography at 15mm f/1.8 instead of 18mm f/1.8, seems a moot point.
The 17-55 could easily have been a 15-50.  The 18-35 could have been a 15-30.
Well, if you're willing to pay about 40% more, than 15-85 is gettable instead of 17-85. But, if you start adding 40% to all the prices of the Sigma/Tamron/etc lenses that go 17-50, most people wouldn't but them. It's one thing to get a $4-500 OS f/2.8 zoom; but by the time it's $6-700 there are other ways to go. Likewise if the 17-55 was a 15-50 that cost $1500. Going those extra few mm's means bigger glass, and more expensive lenses.

If it was so easy to make 15mm zooms, then why is Canon the only one that does?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: bereninga on April 18, 2013, 10:21:00 AM
Shut up and take my money!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Stewbyyy on April 18, 2013, 10:26:22 AM
It's not THAT revolutionary, Olympus have had a 14-35mm F/2 for their DSLRs for a good while and that's unbelievably good quality. I know a professional press photographer who shoots Olympus specifically for that lens.

I don't think Canon would invest their money in pursuing a lens like this, unless Nikon came out with one. I feel Canon would rather make more Rebels with no upgraded features than invest in their devoted/professional crop body shooters. Canon like to deal in extremes, ignorant amateur or needy professional.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: ahsanford on April 18, 2013, 10:37:31 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: infared on April 18, 2013, 10:38:24 AM
I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!! ;D
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Lee Jay on April 18, 2013, 10:44:50 AM
First of all, this is the dumbest gripe I've read in a while.  If you're that unhappy, get a FF with a 24-70 and stop whining. 

Second, it's not even a valid gripe, as Tokina has a 16-28mm constant F2.8 that gets excellent reviews on crop.  Are you really that concerned about the difference between 25.6 and 24?
Yeah, especially since this zoom would do things a 15-85 can't touch; it'd be reasonable to own both as they would be for very different situations.

And since I can't imagine it'd be that great for night photography at 15mm f/1.8 instead of 18mm f/1.8, seems a moot point.
The 17-55 could easily have been a 15-50.  The 18-35 could have been a 15-30.
Well, if you're willing to pay about 40% more, than 15-85 is gettable instead of 17-85. But, if you start adding 40% to all the prices of the Sigma/Tamron/etc lenses that go 17-50, most people wouldn't but them. It's one thing to get a $4-500 OS f/2.8 zoom; but by the time it's $6-700 there are other ways to go. Likewise if the 17-55 was a 15-50 that cost $1500. Going those extra few mm's means bigger glass, and more expensive lenses.

If it was so easy to make 15mm zooms, then why is Canon the only one that does?

Oh, brother.

You realize that 10-20, 10-22, 8-16 and 12-24 are all available in crop lenses, right?

Going a little wider isn't that big a deal, especially if you maintain the total zoom ratio.  Longer is harder with fast lenses as the absolute aperture diameter has to be larger, which is why 70-200s are so expensive.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Ricku on April 18, 2013, 10:47:41 AM
Shut up and don't take my money.

Take my money when there's an equivalent for FF.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: qwerty on April 18, 2013, 10:49:57 AM
This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor.  However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.
(*2) At non-macro distances
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: max on April 18, 2013, 11:03:37 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A

Now that's a lens I would buy.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: ahsanford on April 18, 2013, 11:14:19 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A

Now that's a lens I would buy.


It was offered somewhat in jest.  Half this forum would buy that lens.

- A
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 18, 2013, 11:16:20 AM
I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!! ;D

I'm actually tremendously interested in a new version of their 24-70/2.8 and who knows, maybe something like a 24-90/4. The Tamron is quite good, but Sigma looks like they don't want to be a "second choice" anymore. I love when 3rd-party manufacturers deliver such quality; they set you free from this or that system.

This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor.  However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.
(*2) At non-macro distances

Depending on the price point, the difference between a FF + 24-70 and DX + 18-35 might be what is truly impressive. This lens is not going to reach anything tremendous from an absolute perspective, but it's going to narrow the gap between crop and FF. Actually, I think it would make for an amazing travel lens since it would eliminate the need of a fast prime. If you want to travel light and bring only a crop body and one lens, you either go for a usual standard zoom and live with the slow aperture or you go with something like this.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Krob78 on April 18, 2013, 11:23:29 AM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.
I know what you mean.  It seems like future optics have to get better and better and it's pretty exciting to see unfold before you.

Even if it doesn't live up to all the hype and press, if it does manage f/1.8 across the entire focal/zoom range that's pretty exciting in and of itself.  It makes you a bit excited about that possibly happening in FF lenses, but I seem to think that it's far quicker to happen with the APS-C lenses than the FF, due to the APS-C sensors design and size compared with the FF...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Chosenbydestiny on April 18, 2013, 11:25:09 AM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

+1 Though this might not be the most appealing range for most, it's a game changer that will influence really good stuff in the near future. I'd be happy with something like a 24-50mm f/2 for full frame actually, seeing stuff like this being released makes me confidently look forward to more developments.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: DzPhotography on April 18, 2013, 11:42:52 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A
If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TWI by Dustin Abbott on April 18, 2013, 11:56:45 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A
If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?

You're not wrong, but for those saying this is no big deal, I disagree.  This is something that has not been done before for either crop or FF (an f/1.8 zoom), so to dismiss it outright is absurd.  Yes, developing for full frame is more challenging, but this is clearly a step in the right direction and will put more pressure on Canon.  As a consumer, I see that as a good thing
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: distant.star on April 18, 2013, 11:57:50 AM
I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!! ;D

Me too, me too!!

And a few more thoughts:

1. Haven't seen a single complaint yet about no IS.

2. This is another brick in the foundation I've been building for APS-C as a viable, long term sensor format -- and the coming of an extraordinary 7D2 that just about everyone will want!

3. What are the video implications of this lens? Surely there must be some (don't know since I don't video).

4. Talking about "wiggle room," this seems to go right at Canon's 17-55mm f/2.8, a great lens but one that seems overpriced. (Although the Canon lens does have IS.) If the Sigma is priced under $1K, it may give Canon some pain. And if it's really sharp at f/1.8 it will provide better subject isolation than the Canon at f/2.8 (let the bokeh wars begin!).
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Tom W on April 18, 2013, 12:05:47 PM
Very interesting lens, and a good idea.

Although, I also would like to see a fast, ultrawide full frame zoom instead.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: 9VIII on April 18, 2013, 12:15:10 PM
I'm pretty sure aperture is a fixed definition, doesn't matter if it's a compact P&S or medium format, the same numbers will give the same size lens (focal length divided by lens diameter = aperture) http://en.wikipedia.org/wiki/F-number
 (http://en.wikipedia.org/wiki/F-number)
Compact cameras usually have a flange distance of close to nothing, a 3mm f2 would still be tiny, but with the extreme crop factor of compacts they make it seem like a normal camera.
I just realized that it's probably the form factor of the camera that dictates the size of the sensor on those (the larger the sensor the larger the lenses, and thus the larger the camera would need to be).
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: jcollett on April 18, 2013, 12:16:43 PM
Some have been wondering why APS-C?  Well, Sigma does make cameras and they are all of the crop variety (1.5x) so the glass will natively work.  The 35 1.4 is the oddity; a quite beautiful oddity.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Stephen Melvin on April 18, 2013, 12:27:20 PM
It's not THAT revolutionary, Olympus have had a 14-35mm F/2 for their DSLRs for a good while and that's unbelievably good quality. I know a professional press photographer who shoots Olympus specifically for that lens.

But it's the equivalent of a 28-70 f/4. A pretty mundane lens, wouldn't you say? The Sigma is the equivalent of a FF f/2.8 lens. That's a full stop extra in light gathering power.

I don't think Canon would invest their money in pursuing a lens like this, unless Nikon came out with one. I feel Canon would rather make more Rebels with no upgraded features than invest in their devoted/professional crop body shooters. Canon like to deal in extremes, ignorant amateur or needy professional.

APS format cameras are still the top-selling cameras in C and N's lineups. They really, really need to start making some professional grade lenses for these cameras.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: DzPhotography on April 18, 2013, 12:29:06 PM
Some have been wondering why APS-C?  Well, Sigma does make cameras and they are all of the crop variety (1.5x) so the glass will natively work.  The 35 1.4 is the oddity; a quite beautiful oddity.
I seem to disagree with you there, Sigma has a lot of FF frames in their line-up. And I doubt their own cameras are their main focus when designing lenses...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AprilForever on April 18, 2013, 12:41:25 PM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.


That was kind of my thought: Wow lenses are starting to get really good! THey will most likely be getting a lot better here shortly!

Finally, a zoom better than f2.8. This is actually very exciting. I can see a 50-135 f1.8 coming down the pipeline one day.... And, my hands are now sweating for this and the fabled 7D MK II!!!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Policar on April 18, 2013, 12:47:45 PM
For video this does look nice. 15-40mm is the zoom everyone wants (while 18-85mm is the normal "prime" kit) so this fits in ok. A little wider would be nice. The speed is great, in fact about as fast as the fastest cinema zooms for super35.

REALLY nice to see an affordable WA/UWA for video, even ignoring the zoom. The fastest 16mm-18mm options were previously a stop and a half slower. That's big. Let's see how the image quality is. I compared the 17-55mm f2.8 IS (which I quite like) against the Angenieux Optimo 15-40mm t2.6 yesterday and the Canon doesn't even compare.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: infared on April 18, 2013, 12:56:17 PM
I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!! ;D

I'm actually tremendously interested in a new version of their 24-70/2.8 and who knows, maybe something like a 24-90/4. The Tamron is quite good, but Sigma looks like they don't want to be a "second choice" anymore. I love when 3rd-party manufacturers deliver such quality; they set you free from this or that system.

This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor.  However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.
(*2) At non-macro distances

Depending on the price point, the difference between a FF + 24-70 and DX + 18-35 might be what is truly impressive. This lens is not going to reach anything tremendous from an absolute perspective, but it's going to narrow the gap between crop and FF. Actually, I think it would make for an amazing travel lens since it would eliminate the need of a fast prime. If you want to travel light and bring only a crop body and one lens, you either go for a usual standard zoom and live with the slow aperture or you go with something like this.

I want more Art-Line primes!!!   :)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: syder on April 18, 2013, 01:10:04 PM

And a few more thoughts:

1. Haven't seen a single complaint yet about no IS.

[snip]

3. What are the video implications of this lens? Surely there must be some (don't know since I don't video).


Well 1. has a huge impact on 3. No IS means that it wont be as useful for video as the 17-55 f2.8 IS.

 - in order to get a stable and sharp single frame (from a rig/handheld) you really want Focal length x crop > shutter speed... So for stills IS isn't going to be much of an issue on a fast standard zoom. For video though, you're stuck with a shutter speed of 1/50th (1/60th in NTSC countries), And for video any movement between frames is also visible - hence why for video (if you aren't on a tripod/dolly/slider/crane) having IS is extremely useful.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: babiesphotos on April 18, 2013, 01:17:03 PM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A
If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?

You're not wrong, but for those saying this is no big deal, I disagree.  This is something that has not been done before for either crop or FF (an f/1.8 zoom), so to dismiss it outright is absurd.  Yes, developing for full frame is more challenging, but this is clearly a step in the right direction and will put more pressure on Canon.  As a consumer, I see that as a good thing

Agreed that it's a big deal, as it's not been done before. But I don't think it makes it any more likely for full frame equivalent lens to be made, as that one would have to be larger.
 
Value is in closing the gap between APS-C and full frame, and if you're Nikon shooter, you have 27-52.5 f2.7 FF equivalent, for serious, but not FF money.

And as to why Sigma did this - I think they were looking for a gap where they can play by themselves for awhile. Crop sensor shooters looking for best/fastest glass they can get (in normal range) is probably not a huge market segment, but they own it now.  And then there is a 'hallo' effect of 1.8, increasing value of their lineup. Smart play...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: noncho on April 18, 2013, 02:15:05 PM
After this announcement I'm ready for Sigma 400/4 APS-C smaller and lighter than Canon's  8)   
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Sella174 on April 18, 2013, 02:15:53 PM
My point is, in the film days, only the cheapest kit zooms started at 28, and all the rest started at 24.

There was also a time when the cheap kit lens was 55mm f/1.8, whereas the better one was a 50mm f/1.4 lens.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Sella174 on April 18, 2013, 02:27:34 PM
APS-C is a viable sensor format, just like micro-4/3, and now Sigma is jumping onto it with actual lenses. I might just buy Sigma again ... maybe.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: qwerty on April 18, 2013, 02:39:48 PM
I'm pretty sure aperture is a fixed definition, doesn't matter if it's a compact P&S or medium format, the same numbers will give the same size lens (focal length divided by lens diameter = aperture) http://en.wikipedia.org/wiki/F-number
 (http://en.wikipedia.org/wiki/F-number)
Compact cameras usually have a flange distance of close to nothing, a 3mm f2 would still be tiny, but with the extreme crop factor of compacts they make it seem like a normal camera.
I just realized that it's probably the form factor of the camera that dictates the size of the sensor on those (the larger the sensor the larger the lenses, and thus the larger the camera would need to be).

"Aperture" is a word that is generally mis-used by the photographic community; people often say "aperture" where a pedantic person would say "f-stop".  The aperture for a lens is measured in units of length (e.g. a 200mm f/4 lens has an aperture of 50mm).  The "/" in "f/4" is actually a division sign, so instead of saying " an eff four lens" you should say "a lens with a maximum aperture equal to the focal length divided by four".  Of course, if you said this, virtually noone would understand what you meant; and language is determined by common usage, much to the chagrin of us pedants :)

The aperture (here measured in millimeters) is, in general, not equal to the lens diameter.  You can think of it in crude terms as the diameter of a pin-hole you would make in a pin-hole camera to gather the same amount of light as the subject lens gathers.  However, for telephoto lenses, the maximum aperture (measured in millimeters, not f-stops) will typically be pretty close to the front element diameter.  For normal or wide-angle lenses, that is not the case.  (If you try to do the math yourself, note that the f-stop and focal length quoted by manufacturers are 'marketing numbers', not the real numbers.)

That said, it is a lot easier to make a "fast" (large aperture relative to focal length ) lens for smaller sensor cameras, e.g. 4/3 or P&S.  However, larger format cameras seem to have the edge in terms of the actual aperture (measured in millimeters), and thus light gathering abilities, for a given angle of view.  As I said before, this lens is about the equivalent of a f/2.8 FF lens, which is old-hat in the FF world.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Frage on April 18, 2013, 02:51:14 PM
Some people forget that F aperture is not (just) about bokeh, blur, etc. its about the amount of light which can reach the sensor. In that matter the F value is equivalent between FF and APS-C.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: drjlo on April 18, 2013, 03:04:01 PM
MTF chart for Sigma 18-35 f/1.8

(http://farm9.staticflickr.com/8246/8661493418_87b549b6b0_z.jpg) (http://www.flickr.com/photos/drjlo1/8661493418/)
SigMTF (http://www.flickr.com/photos/drjlo1/8661493418/#) by drjlo1 (http://www.flickr.com/people/drjlo1/), on Flickr
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 18, 2013, 03:57:20 PM
Some people forget that F aperture is not (just) about bokeh, blur, etc. its about the amount of light which can reach the sensor. In that matter the F value is equivalent between FF and APS-C.

I don't think so. Aperture is about the diameter of the blade iris. The amount of light actually conveyed to the sensor is measured in T stops.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 18, 2013, 04:14:57 PM
Some people forget that F aperture is not (just) about bokeh, blur, etc. its about the amount of light which can reach the sensor. In that matter the F value is equivalent between FF and APS-C.

I don't think so. Aperture is about the diameter of the blade iris. The amount of light actually conveyed to the sensor is measured in T stops.

Regardless of the light transmission, an f/1.8 aperture will produce the same exposure at the same ISO and shutter speed whether full frame or crop. I think that's what he means.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Hannes on April 18, 2013, 04:21:38 PM
Now that was an unexpected announcement. Great one none the less and it makes massive amounts of sense for indoor shooting
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 18, 2013, 04:27:20 PM
This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. 

You mean identical DOF. f1.8 will still give more light on APS-C than f/2.8 on full frame.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: mrsfotografie on April 18, 2013, 04:29:56 PM
18mm?  What the heck is it with these idiotic lens makers.  We've got the 17-55, 18-55, 18-135, 18-200, 18-270 and now 18-35.  What do we have that starts at 24mm-equivalent?  The only one I own - the 15-85IS.

f/1.8 sounds interesting, but not if it starts at 18mm!!!

Pass.

Copy that, it reminds me of the 19-35 I've used in the past on APS-C, not a very inspiring zoom range. Better get a 24 mm f/1.4 instead.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 18, 2013, 04:58:17 PM
This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. 

You mean identical DOF. f1.8 will still give more light on APS-C than f/2.8 on full frame.
No. A FF sensor behind an f2.8 FF lens gathers 2.56x as much light as an f2.8 lens does on a 1.6x crop sensor due to the sensors 2.56x bigger surface area. If you only capture a fraction of all that FF f2.8 light by cropping it, well, the obvious happens from the light gathering point of view. The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating. In other words ISO 10,000 on crop is pretty much equal to ISO 25,600 on FF in terms of noise. So feel free to shoot smaller apertures on FF and use higher ISO's to get the same light gathering and noise.

The different amplification levels is a bit like how the Sony NEX 7 and the Sony SLT A77 both share an identical sensor, and give the same exposure with the same shutter speed, aperture and ISO, yet the SLT camera has a semi translucent mirror permanently in front of the sensor, acting like a neutral density filter you can't get rid of. Sony just cranked up the amplifier on the A77 a bit more to make it all seem good - at the expense of noise.

So f1.8 on a 1.6x crop is equivalent to f2.88 on FF in terms of both depth of field and light gathering.

I see this Sigma lens as being a crop alternative to the 24-70 II on FF in just the same way as the 17-55 IS is a crop alternative to the 24-105L on FF. Not quite as fast an effective aperture, and not as wide or as long effective focal lengths. Slightly worse on all fronts when compared to the FF equivalent, but none the less a nice string in the bow for crop sensor users. Lets hope it performs well optically, and I like the idea of an internal zoom on a lens covering the normal range, even if the zoom ring rotates the wrong way :)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Kit. on April 18, 2013, 05:25:55 PM
My point is, in the film days, only the cheapest kit zooms started at 28, and all the rest started at 24.
Actually, the only Canon's standard zoom starting at 24 "in the film days" was EF24-85/3.5-4.5 USM.

Then EF24-70/2.8L was introduced in 2002.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Shane1.4 on April 18, 2013, 06:11:16 PM
Maybe I will get my 60d back out of my bag. That lens sounds awesome!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Danielle on April 18, 2013, 06:17:59 PM
That's pretty awesome. An f1.8 zoom finally. Not that I'll be buying a lens specifically for crop on a hurry but that's a great step in that direction none the less.

Go sigma. I love how tamron and sigma are stepping up.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 18, 2013, 06:30:32 PM
This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. 

You mean identical DOF. f1.8 will still give more light on APS-C than f/2.8 on full frame.
No. A FF sensor behind an f2.8 FF lens gathers 2.56x as much light as an f2.8 lens does on a 1.6x crop sensor due to the sensors 2.56x bigger surface area. If you only capture a fraction of all that FF f2.8 light by cropping it, well, the obvious happens from the light gathering point of view. The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating. In other words ISO 10,000 on crop is pretty much equal to ISO 25,600 on FF in terms of noise. So feel free to shoot smaller apertures on FF and use higher ISO's to get the same light gathering and noise.

The different amplification levels is a bit like how the Sony NEX 7 and the Sony SLT A77 both share an identical sensor, and give the same exposure with the same shutter speed, aperture and ISO, yet the SLT camera has a semi translucent mirror permanently in front of the sensor, acting like a neutral density filter you can't get rid of. Sony just cranked up the amplifier on the A77 a bit more to make it all seem good - at the expense of noise.

So f1.8 on a 1.6x crop is equivalent to f2.88 on FF in terms of both depth of field and light gathering.


Wuh?  ???

[citation needed]
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 18, 2013, 06:32:06 PM
The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating.

What? That's wrong.

A crop f/1.8 lens and a full frame f/1.8 lens will provide exactly the same exposure when used at the same shutter speed and ISO. The full frame exposure WILL NOT be brighter.

You're right about an FF f/2.8 lens having more light gathering ability than a crop f/1.8 lens, but all that light it gathers is spread over a larger sensor, which makes the exposure more than a full stop darker than if you had used an f/1.8 lens.

So in terms of exposure, a f/1.8 lens is brighter than an f/2.8 lens, regardless of sensor size. Sensor size does affect depth of field, but that's a different story.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 18, 2013, 07:15:11 PM
The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating.

What? That's wrong.

A crop f/1.8 lens and a full frame f/1.8 lens will provide exactly the same exposure when used at the same shutter speed and ISO. The full frame exposure WILL NOT be brighter.

You're right about an FF f/2.8 lens having more light gathering ability than a crop f/1.8 lens, but all that light it gathers is spread over a larger sensor, which makes the exposure more than a full stop darker than if you had used an f/1.8 lens.

So in terms of exposure, a f/1.8 lens is brighter than an f/2.8 lens, regardless of sensor size. Sensor size does affect depth of field, but that's a different story.

Exactly. Try it for yourself on a crop body and FF. f1.8 at 1/30 sec at 100 ISO will give you the same exposure on both cameras. FF will not be brighter.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: SwissBear on April 18, 2013, 07:37:37 PM
this is f*** ****some!

all i hope is that the price is in the 3 digit range ;)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: eml58 on April 18, 2013, 08:03:21 PM
I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!! ;D

Yep, tend to agree with all that has been said here, I haven't a use for this Lens as I shoot FF, even my Lads both shoot FF (6D & 5DMK III), but it's the fact that Sigma will make this Lens that's such good News, it should make Canon/Nikon sit up & take note, as has been said, if Sigma can produce their Art Series Lenses going forward as well as they have done with the Art 35f/1.4 (Bought it, Love it, also own the Canon 35f/1.4, the Art is better I feel), then it should be good news for all of us, those that are happy to use non Canon lenses, and those that generally only use Canon lenses and are slowly heading to the poor house due to their personal addiction.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Frage on April 18, 2013, 08:09:25 PM
Some people forget that F aperture is not (just) about bokeh, blur, etc. its about the amount of light which can reach the sensor. In that matter the F value is equivalent between FF and APS-C.

I don't think so. Aperture is about the diameter of the blade iris. The amount of light actually conveyed to the sensor is measured in T stops.

Regardless of the light transmission, an f/1.8 aperture will produce the same exposure at the same ISO and shutter speed whether full frame or crop. I think that's what he means.

Thank you, that´s exactly what I wanted to say. My english is not good enough.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TrumpetPower! on April 18, 2013, 08:21:59 PM
The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating.

What? That's wrong.

A crop f/1.8 lens and a full frame f/1.8 lens will provide exactly the same exposure when used at the same shutter speed and ISO. The full frame exposure WILL NOT be brighter.

You're right about an FF f/2.8 lens having more light gathering ability than a crop f/1.8 lens, but all that light it gathers is spread over a larger sensor, which makes the exposure more than a full stop darker than if you had used an f/1.8 lens.

So in terms of exposure, a f/1.8 lens is brighter than an f/2.8 lens, regardless of sensor size. Sensor size does affect depth of field, but that's a different story.

Exactly. Try it for yourself on a crop body and FF. f1.8 at 1/30 sec at 100 ISO will give you the same exposure on both cameras. FF will not be brighter.

Within minor variation, yes, of course, you'll get the same exposure on both cameras.

The difference, though, is that there will be more noise / grain in the crop version, and the math works out such that the APS-C camera with a 30mm lens at f/1.8 @ 1/30 @ ISO 100 and the 135 camera with a 50mm lens at f/2.8 @ 1/30 @ ISO 260 will give you not only the same exposure, but also the same depth of field but still with less noise and more resolution (assuming the same film stock or pixel pitch).

That means that, with the full frame camera, you can shoot at f/1.8 @ 1/30 @ ISO 100 and get the image with shallower depth of field and much less noise, or you can shoot it at f/2.8 @ 1/60 @ ISO 320 and get the image with the same depth of field and the same noise but a faster shutter speed, or any of another number of variations.

So, basically, you're both right; you're just typing past each other....

It's well worth doing some experimentation in the matter. Set up a still life with controlled lighting and your camera on a tripod -- and don't touch the tripod. Shoot with different focal lengths at different apertures, whether with a zoom or different lenses. Crop them all to the same field of view and scale them all to the same pixel dimensions and compare the results. Figure out what you have to do to match depth of field from the one to the other, and observe what happens to the rest of the image. Be sure to also do a set with low light levels and high ISOs to compensate. (Don't just use a super fast shutter in bright light to get to the high ISOs; that doesn't tell you the whole story and it's not very representative of the real world).

Cheers,

b&
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: roadrunner on April 18, 2013, 08:26:14 PM
I was so excited when I saw this lens. Then so let down when I saw it was APS-C.

After I cooled off a bit, I still realize, this is a very impressive lens. I am so impressed with the way Sigma is going. Can't wait to see this thing tested, though I doubt I will ever buy it. My next 35mm will be the Sigma though for sure, and that's saying alot as I typically don't like buying anything non-canon.

Also, Sigma better have their patent lawyers ready. I hope they don't need them, but if Sigma keeps going the way they are, I wouldn't be surprised to see Canon copying some of this stuff and maybe even put out a firmware update that is coincidentally not compatible with these lenses.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 18, 2013, 08:31:48 PM
The difference, though, is that there will be more noise / grain in the crop version, and the math works out such that the APS-C camera with a 30mm lens at f/1.8 @ 1/30 @ ISO 100 and the 135 camera with a 50mm lens at f/2.8 @ 1/30 @ ISO 260 will give you not only the same exposure, but also the same depth of field but still with less noise and more resolution (assuming the same film stock or pixel pitch).

True, but the full frame camera in this scenario also probably costs 3x more than the crop camera did.  :P

That's why I think this lens is a big deal... Full frame will always be better for sure, but if crop lenses start getting so good that you can get low-light results that are pretty close to a full frame and spend a lot less money, you have a bigger reason to stay with crop.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TrumpetPower! on April 18, 2013, 08:39:29 PM
The difference, though, is that there will be more noise / grain in the crop version, and the math works out such that the APS-C camera with a 30mm lens at f/1.8 @ 1/30 @ ISO 100 and the 135 camera with a 50mm lens at f/2.8 @ 1/30 @ ISO 260 will give you not only the same exposure, but also the same depth of field but still with less noise and more resolution (assuming the same film stock or pixel pitch).

True, but the full frame camera in this scenario also probably costs 3x more than the crop camera did.  :P

That's why I think this lens is a big deal... Full frame will always be better for sure, but if crop lenses start getting so good that you can get low-light results that are pretty close to a full frame and spend a lot less money, you have a bigger reason to stay with crop.

No argument there!

APS-C is a wonderful format. Not one I personally use, but it's a great balance of quality, price, size, weight, and the rest.

Unless your printer takes paper by the three-foot-wide roll and ink by the gallon, there's little need for anything bigger than APS-C. And even then, an APS-C camera is capable of some very impressive results, even if it's pushing its limits.

Cheers,

b&
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Krob78 on April 18, 2013, 09:48:41 PM
I was so excited when I saw this lens. Then so let down when I saw it was APS-C.

After I cooled off a bit, I still realize, this is a very impressive lens. I am so impressed with the way Sigma is going. Can't wait to see this thing tested, though I doubt I will ever buy it. My next 35mm will be the Sigma though for sure, and that's saying alot as I typically don't like buying anything non-canon.

Also, Sigma better have their patent lawyers ready. I hope they don't need them, but if Sigma keeps going the way they are, I wouldn't be surprised to see Canon copying some of this stuff and maybe even put out a firmware update that is coincidentally not compatible with these lenses.
FF would have been good indeed... perhaps they'll shoot one out sometime soon, maybe just a tad wider??  I really love from 16mm and up for my FF and my APS-C...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: fonts on April 18, 2013, 10:03:08 PM
Regardless of the nay-sayers. This lens is awesome. Forget about the kit lens that comes with canon rebels. Once the new M comes out I will marry this lens to it!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Pi on April 18, 2013, 10:42:03 PM
Very limited range. The crop shooters might be better off with two smaller and faster primes.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: fonts on April 18, 2013, 11:24:02 PM
Very limited range. The crop shooters might be better off with two smaller and faster primes.

This lens will probably be around $1000 +/- 200.  50mm (~300) + 35mm 1.4 (900+). I don't know. I would probably stick with the single zoom when it comes to beginners and convenience
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: SpartanII on April 18, 2013, 11:27:26 PM
Very limited range. The crop shooters might be better off with two smaller and faster primes.

That depends on what the price will be upon the release of this 18-35mm lens.

Going the cheap route, the new Sigma 30mm f/1.4 Art is $499. Alternatively there is the option of the 35mm f/1.4 for $899. Another prime in the neighborhood of 15-20mm, specifically a quality one will be a minimum of $1000 (L lens territory). One may be able to get away with a Rokinon or Samyang in this range for $500 perhaps but a person would lose auto-focus.  :)

On a side note I see this one coming in at a minimum of $899.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Pi on April 18, 2013, 11:39:30 PM
Very limited range. The crop shooters might be better off with two smaller and faster primes.

That depends on what the price will be upon the release of this 18-35mm lens.

Going the cheap route, the new Sigma 30mm f/1.4 Art is $499. Alternatively there is the option of the 35mm f/1.4 for $899. Another prime in the neighborhood of 15-20mm, specifically a quality one will be a minimum of $1000 (L lens territory). One may be able to get away with a Rokinon or Samyang in this range for $500 perhaps but a person would lose auto-focus.  :)

On a side note I see this one coming in at a minimum of $899.

What I meant is - since Sigma has the 30/1.4, they could have released an APS-C prime in the 15-18 range. An f/1.8 zoom of this sort could be a big compromise optically.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: pj1974 on April 18, 2013, 11:45:11 PM
Kudos to Sigma for the invention of the first lens f/1.8 zoom lens.  ;)  I've been waiting for such innovation for so long! Well done - and I would hope that the overall image quality is still very good (sharp, contrasty, low vignetting, reasonable distortions, etc).

While the zoom range (18-35) is nothing 'fabulous' on a APS-C, the fact that there is a zoom of this range at f/1.8 is nothing to be sneared at.  (And I must say I like the look of the lens even). I'd prefer it to have a wider zoom range (eg 15mm wide end, and 50mm tele-end) - but I'm very aware of the physical limitations (& size, cost, optical challenges) of that.

Back several years ago, I used my 18-55mm kit lens with my Canon 350D (and I occasionally still use this as a light-as-I-can-DSLR 'travel kit'). I'm not 100% sure what I'd rather have: a 18-35mm f/1.8 or a 24-50mm f/1.8 for APS-C, both would be useful.  I hope that other manufacturers will sit up (or already are!) and technological improvements can continue.

Yay yay yay!   8)

Paul
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Rienzphotoz on April 18, 2013, 11:57:27 PM
AWESOME
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: SpartanII on April 19, 2013, 12:16:33 AM
Very limited range. The crop shooters might be better off with two smaller and faster primes.

That depends on what the price will be upon the release of this 18-35mm lens.

Going the cheap route, the new Sigma 30mm f/1.4 Art is $499. Alternatively there is the option of the 35mm f/1.4 for $899. Another prime in the neighborhood of 15-20mm, specifically a quality one will be a minimum of $1000 (L lens territory). One may be able to get away with a Rokinon or Samyang in this range for $500 perhaps but a person would lose auto-focus.  :)

On a side note I see this one coming in at a minimum of $899.

What I meant is - since Sigma has the 30/1.4, they could have released an APS-C prime in the 15-18 range. An f/1.8 zoom of this sort could be a big compromise optically.

Ah I understand.

I did come across an old non fisheye 15mm produced by Sigma on ebay. Cannot recall if it was a FF issue or not.

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Tabercil on April 19, 2013, 01:05:55 AM
This lens looks very tempting for me to get - it depends on what the end price is. My primary photography subject is pro wrestling, usually taken ringside. I currently use a Sigma 17-70 lens and a flash, but I know I take a large chunk of my shots out at the wide end of the zoom. Case in point, I had 285 "keepers" at the most recent show and 213 of them were taken at 35 or lower. What excites me is the possibility of marrying this lens with a 7D (or more likely the 7D2 whenever it's announced) and be able to ditch the flash altogether...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 19, 2013, 01:18:53 AM
The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating.

What? That's wrong.

A crop f/1.8 lens and a full frame f/1.8 lens will provide exactly the same exposure when used at the same shutter speed and ISO. The full frame exposure WILL NOT be brighter.

You're right about an FF f/2.8 lens having more light gathering ability than a crop f/1.8 lens, but all that light it gathers is spread over a larger sensor, which makes the exposure more than a full stop darker than if you had used an f/1.8 lens.

So in terms of exposure, a f/1.8 lens is brighter than an f/2.8 lens, regardless of sensor size. Sensor size does affect depth of field, but that's a different story.

Exactly. Try it for yourself on a crop body and FF. f1.8 at 1/30 sec at 100 ISO will give you the same exposure on both cameras. FF will not be brighter.
Hey guys, read what I wrote. I said f1.8 on crop is brighter than f2.8 on full frame when both have the same shutter speed and ISO, then you start telling me that I'm wrong to say FF is brighter when they're both at f1.8 and the same shutter speed and ISO. I didn't say that, so what gives? I went to great lengths to explain that at the same aperture, shutter speed and ISO, they both expose the same due to the different light gathering of the format being compensated for by the amplifiers being set different. If you can look past that same exposure settings between formats and start to use the higher ISO's with lower noise levels this lower amplification of FF rewards you with, you'll find the true nature of the light gathering of FF lenses on FF sensors.

If you really think you can freely quote focal lengths in 35mm equivalent without quoting apertures in 35mm equivalents, then you're sounding very much like the Panasonic marketing department:
(http://www3.picturepush.com/photo/a/12280946/1024/Picture-Box/highres-panasonic-lumix-fz200-8-1342452955.jpg)
Surely you know that taking this small sensor, large aperture thing to extremes like this does not result in this Panasonic FZ200 having a lens equivalent of a 600mm f2.8 at full zoom, as Panasonic would like you to think? In terms of framing, yes. In terms of exposure due to ISO tweaking of the sensor, yes. In terms if DoF, no. In terms if light gathering, no! There's no way that a 'slow' Canon 600/4 II on a 1D X as a package gathers less light than that 'f2.8' lens/sensor combo of the Panasonic. Yes, both at f4, 1/1000th of a sec, they'll both have to use an identical ISO to expose the same, but look past using the same rated ISO and guess which combo would work best to get clean images at high shutter speeds in low light?

If you can understand that, then surely you can see the 1.6x crop gives just over a stop less light gathering than a full frame sensor - making f1.8 on crop equal in light capturing terms to an aperture 1.6x smaller on FF - f2.88.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: verysimplejason on April 19, 2013, 02:12:45 AM

I was flummoxed when I heard that this thing is APS-C only.  Why?!  If this is a premium lens aimed at serious shooters, why go crop?  This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys?  That would likely have a larger interest level.

- A

You have to wait.  Something tells me that if they can do it in APS-C, they'll soon do it for FF.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 02:32:43 AM

Surely you know that taking this small sensor, large aperture thing to extremes like this does not result in this Panasonic FZ200 having a lens equivalent of a 600mm f2.8 at full zoom, as Panasonic would like you to think? In terms of framing, yes. In terms of exposure due to ISO tweaking of the sensor, yes. In terms if DoF, no. In terms if light gathering, no! There's no way that a 'slow' Canon 600/4 II on a 1D X as a package gathers less light than that 'f2.8' lens/sensor combo of the Panasonic. Yes, both at f4, 1/1000th of a sec, they'll both have to use an identical ISO to expose the same, but look past using the same rated ISO and guess which combo would work best to get clean images at high shutter speeds in low light?

If you can understand that, then surely you can see the 1.6x crop gives just over a stop less light gathering than a full frame sensor - making f1.8 on crop equal in light capturing terms to an aperture 1.6x smaller on FF - f2.88.

Aperture is just a way to measure the diameter of the iris blade. It's connected to, but it doesn't measure, the real amount of light gathered. This is why T-stops were invented.

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: pwp on April 19, 2013, 02:40:33 AM
Well good! If you shoot APS-C...
Though I may be inspired to get a 7DII.
But is a FF f/1.8 zoom next?

-PW
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: LifeAfter on April 19, 2013, 04:45:17 AM
Imagine what could this lens do with a Metabones speed booster!!!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: CarlTN on April 19, 2013, 04:52:51 AM
I'm really excited about this lens, and I don't even own a crop body.  I'm excited about the implications for the future.  If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics.  Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers.  The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

+1
My complaint is, it should have simply been a full frame lens.  It still would have been relatively affordable, even if its street price was just under $2k.  Why?  Because if Canon made a full frame lens like this, it would be closer to $3k or even above 3k, and (very likely) not much better, if any.

I can certainly see why it's not full frame.  The smaller pixels and sensor, benefit greatly from a faster lens...because they are starved for light by the nature of their size.

I have been calling for a fast zoom, myself.  Perhaps Tamron will do the full frame version?  I want something bigger and more exotic though, and by the time it ever got designed and hit the market...I will probably be able to afford one: 90-150mm f/0.9 with..."OS"...It's just a fantasy of mine, not realistic that anything like this will ever exist.  Perhaps by 2017 or so, someone will build something...
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 19, 2013, 05:37:51 AM
Aperture is just a way to measure the diameter of the iris blade. It's connected to, but it doesn't measure, the real amount of light gathered. This is why T-stops were invented.
T-stops are a measured version of light as opposed to f stops which are theoretical - so they take into account the transmission of light, including effects such as reflections and tinting of glass. However, even T-stops don't take into account the size of the imaging circle or the size of the sensor. That's why a 24-70/2.8 II on FF is more than a worthy rival to this 18-35/1.8 on crop, yet if you mount the same 24-70/2.8 II on crop, it is not.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 07:08:15 AM
Aperture is just a way to measure the diameter of the iris blade. It's connected to, but it doesn't measure, the real amount of light gathered. This is why T-stops were invented.
T-stops are a measured version of light as opposed to f stops which are theoretical - so they take into account the transmission of light, including effects such as reflections and tinting of glass. However, even T-stops don't take into account the size of the imaging circle or the size of the sensor. That's why a 24-70/2.8 II on FF is more than a worthy rival to this 18-35/1.8 on crop, yet if you mount the same 24-70/2.8 II on crop, it is not.

Exactly. F-stops = T-stops in an ideal lens; in practical terms they are a better measure of DoF than they are of light transmission.

I don't agree with the rest though. Or better, I'm not quite sure what you mean.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: indigo9 on April 19, 2013, 08:10:01 AM
Hey guys, read what I wrote. I said f1.8 on crop is brighter than f2.8 on full frame when both have the same shutter speed and ISO, then you start telling me that I'm wrong to say FF is brighter when they're both at f1.8 and the same shutter speed and ISO. I didn't say that, so what gives? I went to great lengths to explain that at the same aperture, shutter speed and ISO, they both expose the same due to the different light gathering of the format being compensated for by the amplifiers being set different. If you can look past that same exposure settings between formats and start to use the higher ISO's with lower noise levels this lower amplification of FF rewards you with, you'll find the true nature of the light gathering of FF lenses on FF sensors.
...

So I was about to chime in that rs is wrong and actually sat down to prove it only to realise that he's right (although not terribly clear).

For the same angle of view:

80mm 1.0x [FF]      @ f/2 aperture = 40mm diam pupil
50mm 1.6x [APSC] @ f/2 aperture = 25mm diam pupil

Given that we have the same angle of view, the amount of light falling on the sensor is purely a function of the pupil diameter. f/2 on full frame is not the same as f/2 on crop.

Exposition
In case you're still not convinced, now assume that you have a FF and APSC sensor using the same production process & the same overall resolution -- they will have the same sensitivity per photon. If you take a shot with the same shutter speed, given that more light falls on the full frame sensor you would expect to use less sensor signal amplification [ie a lower ISO setting].

Alternate exposition
Or looking it at another way, if we keep the sensor signal amplification [ISO setting] constant, more light has fallen on each FF sensor pixel [same resolution remember], so you'll have to reduce the shutter speed of the FF to get the same exposure as APSC. Clearly FF f/2 is not the same as APSC f/2.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 08:25:25 AM
Hey guys, read what I wrote. I said f1.8 on crop is brighter than f2.8 on full frame when both have the same shutter speed and ISO, then you start telling me that I'm wrong to say FF is brighter when they're both at f1.8 and the same shutter speed and ISO. I didn't say that, so what gives? I went to great lengths to explain that at the same aperture, shutter speed and ISO, they both expose the same due to the different light gathering of the format being compensated for by the amplifiers being set different. If you can look past that same exposure settings between formats and start to use the higher ISO's with lower noise levels this lower amplification of FF rewards you with, you'll find the true nature of the light gathering of FF lenses on FF sensors.
...



80mm 1.0x [FF]      @ f/2 aperture = 40mm diam pupil
50mm 1.6x [APSC] @ f/2 aperture = 25mm diam pupil



He is not.

Quote from: Wikipedia
In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture[1]) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil.

You can't compare different focal lenghts. A 50mm is a 50mm both on crop and FF. However, being the former smaller, you crop the edges to a degree which would be equivalent to the angle of view of a 80mm on FF. This is a quick way to grasp the concept, but it's not exact in a way that you can make calculations.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: zim on April 19, 2013, 08:30:23 AM
and bring on a 24-70 2.8 IS art line for FF I hope it's more 'when' than 'if'
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 19, 2013, 08:35:54 AM
Hey guys, read what I wrote. I said f1.8 on crop is brighter than f2.8 on full frame when both have the same shutter speed and ISO, then you start telling me that I'm wrong to say FF is brighter when they're both at f1.8 and the same shutter speed and ISO. I didn't say that, so what gives? I went to great lengths to explain that at the same aperture, shutter speed and ISO, they both expose the same due to the different light gathering of the format being compensated for by the amplifiers being set different. If you can look past that same exposure settings between formats and start to use the higher ISO's with lower noise levels this lower amplification of FF rewards you with, you'll find the true nature of the light gathering of FF lenses on FF sensors.
...



80mm 1.0x [FF]      @ f/2 aperture = 40mm diam pupil
50mm 1.6x [APSC] @ f/2 aperture = 25mm diam pupil



He is not.

Quote from: Wikipedia
In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture[1]) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil.

You can't compare different focal lenghts. A 50mm is a 50mm both on crop and FF. However, being the former smaller, you crop the edges to a degree which would be equivalent to the angle of view of a 80mm on FF. This is a quick way to grasp the concept, but it's not exact in a way that you can make calculations.
Thanks indigo9, nice explanation. Albi86 - a 1.6x crop camera crops the FoV, so to get the same framing, you have to use a different focal length. This 18-35 crop lens is a rival to a 24-70 on FF, not a 16-35. 80mm on FF does frame the same as 50mm on crop - and if they both have the same aperture, the 80mm lens has to have a bigger entrance pupil.

And using indigo9's simple (yet still misunderstood) explanation, to compare the 18-35/1.8 to the 24-70/2.8 on FF we'd need to set them both to a focal length to give an equal field of view. So for the sake of this example, lets use the long end of the Sigma's zoom - set the 18-35/1.8 to 35mm, which is equivalent of 56mm on the 24-70. We get the following:

56mm 1.0x [FF]      @ f/2.8 aperture = 20mm diam pupil
35mm 1.6x [APSC] @ f/1.8 aperture = 19.4mm diam pupil

So, vaguely less light gathering from the new Sigma lens, as well as a vaguely wider DoF.

Neuro - do you want to chime in at this point? People respect your opinion  ;)

And as I said before though, this is a very interesting lens, and its a great option for crop sensor users - while it lets in slightly less light and has a narrower zoom range than the 24-70/2.8, its a great alternative to moving to a more expensive body, and the internal zoom is a great feature for a normal lens.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 08:47:52 AM
...

You are mixing two concepts that are unrelated.

If we talk about framing, then you're right. The smaller effective aperture is the reason why DoF is bigger on crop at a given aperture and angle of view (note that I didn't say focal length).

However, framing has nothing to do with light gathering. f-stops are a function of focal length, not angle of view. A 50mm is a 50mm on every camera. It's the angle of view that changes in relation to sensor size, not the focal length.

Another quote from Wikipedia:
Quote
A 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A 200 mm focal length f/4 lens has an entrance pupil diameter of 50 mm. The 200 mm lens's entrance pupil is larger than that of the 100 mm lens, but given the same light transmission efficiency, both will produce the same illuminance at the focal plane when imaging a scene of a given luminance.

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Sella174 on April 19, 2013, 09:16:55 AM
I think the wheels come off because we are using "full-frame" lenses on "crop-frame" cameras, and insist on comparing everything to the "35mm" (aka "full-frame") format.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 09:23:43 AM
I think the wheels come off because we are using "full-frame" lenses on "crop-frame" cameras, and insist on comparing everything to the "35mm" (aka "full-frame") format.

This can be done with no problems. The important thing is not to confuse focal length with angle of view. We can say that a 50mm gives you the same framing ( = angle of view) of a 80mm on FF; however, other parameters related specifically to focal length and not to angle of view are not affected.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 19, 2013, 09:36:00 AM
...

You are mixing two concepts that are unrelated.

If we talk about framing, then you're right. The smaller effective aperture is the reason why DoF is bigger on crop at a given aperture and angle of view (note that I didn't say focal length).

However, framing has nothing to do with light gathering. f-stops are a function of focal length, not angle of view. A 50mm is a 50mm on every camera. It's the angle of view that changes in relation to sensor size, not the focal length.

Another quote from Wikipedia:
Quote
A 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A 200 mm focal length f/4 lens has an entrance pupil diameter of 50 mm. The 200 mm lens's entrance pupil is larger than that of the 100 mm lens, but given the same light transmission efficiency, both will produce the same illuminance at the focal plane when imaging a scene of a given luminance.
But to compare a crop lens, crop sensor combo to a FF lens, FF sensor combo, there's no point in comparing two with different framing - otherwise you'd be arguing this 18-35 crop lens is a direct equivalent of a 16-35 FF lens on FF.

To exaggerate, is a 100mm f5.6 large format lens with its huge image circle the same as a 100mm f5.6 lens and its tiny image circle on a compact? Is it wrong to compare lenses which give the same framing? Surely from a photographers point of view, they're two very different lenses?

Wikipedia doesn't take into account imaging circle in that equation you're quoting. The aperture of a lens is a bit like working out the speed of water in a hose pipe. The imaging circle is a bit like the diameter of the pipe. Widen the pipe and keep the speed the same, you get more coming through.

Or think about it like this - imagine a photo taken with a FF lens and a FF sensor. Now you take that same photo and you crop out just the centre 40% - you've taken away 60% of the image - which is also 60% of the light that passed through that FF lens. You're left with only 40% of the light. That's what crop does. You need a faster lens on crop to make it capture the same amount of light in that smaller area.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 19, 2013, 10:14:27 AM


Given that we have the same angle of view, the amount of light falling on the sensor is purely a function of the pupil diameter. f/2 on full frame is not the same as f/2 on crop.

Exposition
In case you're still not convinced, now assume that you have a FF and APSC sensor using the same production process & the same overall resolution -- they will have the same sensitivity per photon. If you take a shot with the same shutter speed, given that more light falls on the full frame sensor you would expect to use less sensor signal amplification [ie a lower ISO setting].



More light falls on the FF sensor but it is spread out over a bigger area. actual intensity (or in this case it helps to think about it as density) of the light is the same.

The only reason why you are able to use a higher ISO on FF is because the pixels are larger on FF which means better signal to noise.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 11:13:28 AM
...

You are mixing two concepts that are unrelated.

If we talk about framing, then you're right. The smaller effective aperture is the reason why DoF is bigger on crop at a given aperture and angle of view (note that I didn't say focal length).

However, framing has nothing to do with light gathering. f-stops are a function of focal length, not angle of view. A 50mm is a 50mm on every camera. It's the angle of view that changes in relation to sensor size, not the focal length.

Another quote from Wikipedia:
Quote
A 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A 200 mm focal length f/4 lens has an entrance pupil diameter of 50 mm. The 200 mm lens's entrance pupil is larger than that of the 100 mm lens, but given the same light transmission efficiency, both will produce the same illuminance at the focal plane when imaging a scene of a given luminance.
But to compare a crop lens, crop sensor combo to a FF lens, FF sensor combo, there's no point in comparing two with different framing - otherwise you'd be arguing this 18-35 crop lens is a direct equivalent of a 16-35 FF lens on FF.

You can compare what you want, as long as you it correctly. The way you do it is the way you can compare angles of view. This is fine as long as you don't make the mistake to consider angle of view = focal length and to put this value into a f/stop calculation.

To exaggerate, is a 100mm f5.6 large format lens with its huge image circle the same as a 100mm f5.6 lens and its tiny image circle on a compact? Is it wrong to compare lenses which give the same framing? Surely from a photographers point of view, they're two very different lenses?

Focal length is what it is. You can mount an old Zeiss for Hasselblad lens on your Canon camera and the focal length will not change. It would give you the same framing of a 100mm Canon lens.

Wikipedia doesn't take into account imaging circle in that equation you're quoting. The aperture of a lens is a bit like working out the speed of water in a hose pipe. The imaging circle is a bit like the diameter of the pipe. Widen the pipe and keep the speed the same, you get more coming through.

More flow, but not more pressure. Same with light: you get more light coming in in total, but the amount of light / surface of the sensor would be the same. Any extra light that comes in will not affect exposure.

Or think about it like this - imagine a photo taken with a FF lens and a FF sensor. Now you take that same photo and you crop out just the centre 40% - you've taken away 60% of the image - which is also 60% of the light that passed through that FF lens. You're left with only 40% of the light. That's what crop does. You need a faster lens on crop to make it capture the same amount of light in that smaller area.

Same as above. A smaller sensor is actually a smaller mouth to feed. This is why you can have compact cameras with 1" sensor and f/1.8 lenses.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 19, 2013, 11:29:32 AM
You can compare what you want, as long as you it correctly. The way you do it is the way you can compare angles of view. This is fine as long as you don't make the mistake to consider angle of view = focal length and to put this value into a f/stop calculation.
Angle of view is a combination of focal length and sensor size. If we're talking about two different sized sensors, to get the same angle of view, we have to adjust the focal length to suit.

Focal length is what it is. You can mount an old Zeiss for Hasselblad lens on your Canon camera and the focal length will not change. It would give you the same framing of a 100mm Canon lens.
You're looking at it the wrong way here - while the 100mm Zeiss frames the same as the 100mm Canon on the Canon SLR, it frames very different from how it would on the Hasselbald. On the Canon, you've cropped out a fair old proportion of the image circle, resulting in much of the light being cropped out and a narrower FoV.

More flow, but not more pressure. Same with light: you get more light coming in in total, but the amount of light / surface of the sensor would be the same. Any extra light that comes in will not affect exposure.
That's my exact point - the intensity of the light at any area of the sensor isn't greater, its just there's a bigger area of it, so in total more light is captured by the system.

Same as above. A smaller sensor is actually a smaller mouth to feed. This is why you can have compact cameras with 1" sensor and f/1.8 lenses.
Again, it looks like you've nearly got it here - it does need that faster aperture to make it equivalent.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 11:47:10 AM

Angle of view is a combination of focal length and sensor size. If we're talking about two different sized sensors, to get the same angle of view, we have to adjust the focal length to suit.



Exactly. And you have to decide if we're talking about focal length or angle of view. You can't freely interchange the two concepts, because they are two different things. You can compare one to the other, but within limits.

Focal length is a property of the lens, and the lens alone. Whatever is a function of focal length, is not affected by the sensor in your camera, which - as you said - instead will affect the angle of view.

A Nikon 1 10mm f/2.8 lens will have an equivalent focal length (read: angle of view) of a 27mm lens on FF, but it will be nevertheless a 10mm lens. Assuming transmission is the same, the exposure would be the same for this lens and a 10mm F/2.8 lens on FF. The Nikon 1 lens can be smaller because the sensor is smaller. The total amount of light gathered by a FF will be more, but the amount of light hitting the sensor / surface of the sensor would be the same. You could mount the FF lens on the Nikon 1 and it would be the same - because the extra light will fall off the sensor. That's why exposure is not affected.

If you now transpose this concept to this lens, you will understand that exposure-wise a f/1.8 lens is a f/1.8 lens disregarding of the system. This, again, is because f-stops depend on focal length and focal length is a parameter of the lens and not of the camera.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: insanitybeard on April 19, 2013, 12:41:29 PM
Debate regarding the light gathering ability of this lens and equivalent DOF vs FF aside, I must admit this is an interesting lens. This is coming from somebody who up until this point has only considered Canon glass. Maybe it will give Canon a push to put out some more high quality and fast dedicated crop lenses of it's own. The implications of using this lens on a crop camera cannot be ignored, if it is good optically.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AprilForever on April 19, 2013, 12:45:06 PM
What makes this lens epic is that there is no equivalent FF lens. In very low light, this can focus when f2.8 cannot!!!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 19, 2013, 12:49:44 PM
What makes this lens epic is that there is no equivalent FF lens. In very low light, this can focus when f2.8 cannot!!!

+1

It's epic that it takes crop shooters where they've never been before.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Lee Jay on April 19, 2013, 02:07:41 PM
What makes this lens epic is that there is no equivalent FF lens. In very low light, this can focus when f2.8 cannot!!!

No cameras I know of have f/1.8 AF sensors.  f/2.8 sensors "see" at f/2.8 regardless of the actual f-stop of the lens.  An f/1.4 lens is no brighter to f/2.8 AF sensors than an f/2.8 lens is.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: indigo9 on April 19, 2013, 02:20:48 PM

Exactly. And you have to decide if we're talking about focal length or angle of view. You can't freely interchange the two concepts, because they are two different things. You can compare one to the other, but within limits.

Sensor dimensions taken from: http://en.wikipedia.org/wiki/Full-frame_digital_SLR (http://en.wikipedia.org/wiki/Full-frame_digital_SLR)
FoV/Focal Length formulas: http://paulbourke.net/miscellaneous/lens/ (http://paulbourke.net/miscellaneous/lens/)

Calculations:
(Using an 81mm lens here to be more accurate, 36/22.2 = 1.62 crop factor)

APSC sensor: 22.2mm width, focal length 50mm = 0.4369 radians = 25.0 degrees
Full Frame sensor: 36mm width, focal length 81mm = 0.4373 radians = 25.1 degrees

Focal length and Field of View are the same thing. The only reason they might not match in practice is because manufacturers don't quite tell the truth and the advertised focal length is slightly different from what they say (if it's 52mm, they're going to advertise it as a 50mm anyway)


A Nikon 1 10mm f/2.8 lens will have an equivalent focal length (read: angle of view) of a 27mm lens on FF, but it will be nevertheless a 10mm lens. Assuming transmission is the same, the exposure would be the same for this lens and a 10mm F/2.8 lens on FF.

A Nikon 1 10mm f/2.8 lens will have a pupil diameter of 3.57mm.

A 27mm f2.8 lens will have a pupil diameter of 9.64mm.

There are 2.7^2=7.3 times as many photons are coming through that 27mm lens as through the 10mm lens at the same f stop. Since the same proportion of those photons falling on the sensor is the same [same aspect ratios fitting in a circular aperture], the full frame sensor is receiving 7.3 times as many photons at the same f-stop.

The fact that one sensor is larger or smaller is completely irrelevant -- both sensors are covering the same proportion of the image circle (because we're talking about 35mm equivalent focal lengths here -- if you want to argue proportion of image circle covered then you need to do the comparisons using the same focal lengths -- see below)

The Nikon 1 lens can be smaller because the sensor is smaller. The total amount of light gathered by a FF will be more, but the amount of light hitting the sensor / surface of the sensor would be the same.

See above -- the amount of light (ie photons) hitting the sensor is most definitely not the same. The physical aperture size and the field of view are the only 2 things that control how many photons go through the lens.

You could mount the FF lens on the Nikon 1 and it would be the same - because the extra light will fall off the sensor.

Huh? A Nikon 1 sensor is 2.72x2.72 = 7.44 times smaller -- 87% of photons that would be hitting a FF sensor are being ignored. Assuming sensors are equivalent technology, at the same shutter speed the simple fact is that the Nikon 1 will have to amplify the signal coming off the sensor 7 times more than the full frame camera to get a proper exposure. How is this possibly equivalent?

That's why exposure is not affected.

More photons hitting the sensor = more electrons being excited = less amplification necessary to properly expose an image = less amplification of background sensor noise.

Note that I deliberately haven't mentioned ISO settings at all -- ISO settings are just calibrated labels to measure how much sensor signal amplification the camera needs to perform to properly expose a scene to a certain level, they are not an inherent property of the sensor itself. Go to dxomark and compare the SNR on a Canon 5D2 and a 60D -- the 60D is far noisier despite having a newer sensor, because ISO 1600 on a 60D actually means a lot more signal amplification than ISO 1600 on a 5D2. The ISO number itself is irrelevant, what is relevant is how much noise is amplified along with the useful signal.

If you now transpose this concept to this lens, you will understand that exposure-wise a f/1.8 lens is a f/1.8 lens disregarding of the system. This, again, is because f-stops depend on focal length and focal length is a parameter of the lens and not of the camera.

Yes, a f/1.8 lens is a f/1.8 lens regardless of the system. A f/1.8 lens on a full frame will perform better than a f/1.8 lens on crop with equivalent focal lengths though, and that's what the original question was.

Imagine that tomorrow I introduce a new camera system for amateur astronomers called "Super 100x35mm", sensor dimensions 360mm x 240mm, same ~4000x2800px resolution as a crop system. I stick 35mm-equivalent 50mm focal length lens on it, which for this system would be a 500m f/2.8. The pupil diameter of this lens is 178mm -- this pupil is 10 times wider than a full frame lens. According to the logic above, the fact that this pupil & sensor has 262 times more light gathering capability than a crop 32mm f/2.8 lens is irrelevant; "exposure-wise" all f/2.8 lenses are equivalent? Does this really sound sensible to you?

If that's the case, why are astronomy telescopes so wide?




The original question was whether a crop camera with a given lens at f/2.8 performs the same as an equivalent focal length f/2.8 full frame. The answer is no, for equivalent focal lengths at the same f-stop the full frame sensor receives a lot more light and so gives less noise. In light of that, rs is right -- the lens might be nice for someone like me who only owns a crop camera but if you care terribly about low light performance then you should be on full frame.


Native sensor ISO? Let's not open *that* can of worms
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: michi on April 19, 2013, 02:45:34 PM
Lots of high tech talk I am not privy to understand or care to understand.  The lens however seems great.  Impressed with Sigma.  Unfortunately I have decided to go and stay with full frame.  If anything remotely similar was available for full frame, I would be all over it.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 19, 2013, 04:04:47 PM
There has been a lot of nonsense on this thread. It's pointless contributing now because the ones spreading the nonsense have entrenched themselves so deeply that they have no prospect of coming out of this with any dignity or credibility.

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: CarlTN on April 19, 2013, 04:33:27 PM
There has been a lot of nonsense on this thread. It's pointless contributing now because the ones spreading the nonsense have entrenched themselves so deeply that they have no prospect of coming out of this with any dignity or credibility.

Let's not say these people have no dignity...that's personal and uncalled for.  They're simply sharing their opinion.

However, I agree...the discussion has turned rather silly it seems.  And there's nothing "epic" about this lens.  "Epic" is such a silly slang word these days, overused by teenage pop culture...it's time to retire it.

via google: ep·ic 

/ˈepik/

Noun

A long poem, typically derived from oral tradition, narrating the deeds and adventures of heroic or legendary figures or the history of...

http://www.merriam-webster.com/dictionary/epic (http://www.merriam-webster.com/dictionary/epic)

The word really does not apply.  There actually have been other fast zooms, such as Olympus' f/2.  Just because this is the first f/1.8 zoom, does not make it "epic".

I mean, the above exchanges seem to have to do with light intensity, etc.  A crop sensor uses only part of a full frame lens' image circle.  Since the lens in question, is designed for a smaller image circle, then it can't really be compared to a lens that is designed to output a larger image circle to a larger sensor.  Can it?  Sure, you can attempt to calculate, and approximate...but does it really matter as much as those above think it does?  No.

Let's just all go full frame, and forget crop sensors, especially for anything less than telephoto focal lengths (such as over 100mm).
 
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 19, 2013, 05:06:04 PM
There has been a lot of nonsense on this thread. It's pointless contributing now because the ones spreading the nonsense have entrenched themselves so deeply that they have no prospect of coming out of this with any dignity or credibility.

Let's not say these people have no dignity...that's personal and uncalled for.  They're simply sharing their opinion.


Yes, I shouldn't have put it that way. Apologies.

(Although, describing what f/1.8 means - whether on FF or APS-C - ought to be a matter of fact, not opinion).
 
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: 9VIII on April 19, 2013, 09:27:05 PM

Exactly. And you have to decide if we're talking about focal length or angle of view. You can't freely interchange the two concepts, because they are two different things. You can compare one to the other, but within limits.

Sensor dimensions taken from: http://en.wikipedia.org/wiki/Full-frame_digital_SLR (http://en.wikipedia.org/wiki/Full-frame_digital_SLR)
FoV/Focal Length formulas: http://paulbourke.net/miscellaneous/lens/ (http://paulbourke.net/miscellaneous/lens/)

Calculations:
(Using an 81mm lens here to be more accurate, 36/22.2 = 1.62 crop factor)

APSC sensor: 22.2mm width, focal length 50mm = 0.4369 radians = 25.0 degrees
Full Frame sensor: 36mm width, focal length 81mm = 0.4373 radians = 25.1 degrees

Focal length and Field of View are the same thing. The only reason they might not match in practice is because manufacturers don't quite tell the truth and the advertised focal length is slightly different from what they say (if it's 52mm, they're going to advertise it as a 50mm anyway)


A Nikon 1 10mm f/2.8 lens will have an equivalent focal length (read: angle of view) of a 27mm lens on FF, but it will be nevertheless a 10mm lens. Assuming transmission is the same, the exposure would be the same for this lens and a 10mm F/2.8 lens on FF.

A Nikon 1 10mm f/2.8 lens will have a pupil diameter of 3.57mm.

A 27mm f2.8 lens will have a pupil diameter of 9.64mm.

There are 2.7^2=7.3 times as many photons are coming through that 27mm lens as through the 10mm lens at the same f stop. Since the same proportion of those photons falling on the sensor is the same [same aspect ratios fitting in a circular aperture], the full frame sensor is receiving 7.3 times as many photons at the same f-stop.

The fact that one sensor is larger or smaller is completely irrelevant -- both sensors are covering the same proportion of the image circle (because we're talking about 35mm equivalent focal lengths here -- if you want to argue proportion of image circle covered then you need to do the comparisons using the same focal lengths -- see below)

The Nikon 1 lens can be smaller because the sensor is smaller. The total amount of light gathered by a FF will be more, but the amount of light hitting the sensor / surface of the sensor would be the same.

See above -- the amount of light (ie photons) hitting the sensor is most definitely not the same. The physical aperture size and the field of view are the only 2 things that control how many photons go through the lens.

You could mount the FF lens on the Nikon 1 and it would be the same - because the extra light will fall off the sensor.

Huh? A Nikon 1 sensor is 2.72x2.72 = 7.44 times smaller -- 87% of photons that would be hitting a FF sensor are being ignored. Assuming sensors are equivalent technology, at the same shutter speed the simple fact is that the Nikon 1 will have to amplify the signal coming off the sensor 7 times more than the full frame camera to get a proper exposure. How is this possibly equivalent?

That's why exposure is not affected.

More photons hitting the sensor = more electrons being excited = less amplification necessary to properly expose an image = less amplification of background sensor noise.

Note that I deliberately haven't mentioned ISO settings at all -- ISO settings are just calibrated labels to measure how much sensor signal amplification the camera needs to perform to properly expose a scene to a certain level, they are not an inherent property of the sensor itself. Go to dxomark and compare the SNR on a Canon 5D2 and a 60D -- the 60D is far noisier despite having a newer sensor, because ISO 1600 on a 60D actually means a lot more signal amplification than ISO 1600 on a 5D2. The ISO number itself is irrelevant, what is relevant is how much noise is amplified along with the useful signal.

If you now transpose this concept to this lens, you will understand that exposure-wise a f/1.8 lens is a f/1.8 lens disregarding of the system. This, again, is because f-stops depend on focal length and focal length is a parameter of the lens and not of the camera.

Yes, a f/1.8 lens is a f/1.8 lens regardless of the system. A f/1.8 lens on a full frame will perform better than a f/1.8 lens on crop with equivalent focal lengths though, and that's what the original question was.

Imagine that tomorrow I introduce a new camera system for amateur astronomers called "Super 100x35mm", sensor dimensions 360mm x 240mm, same ~4000x2800px resolution as a crop system. I stick 35mm-equivalent 50mm focal length lens on it, which for this system would be a 500m f/2.8. The pupil diameter of this lens is 178mm -- this pupil is 10 times wider than a full frame lens. According to the logic above, the fact that this pupil & sensor has 262 times more light gathering capability than a crop 32mm f/2.8 lens is irrelevant; "exposure-wise" all f/2.8 lenses are equivalent? Does this really sound sensible to you?

If that's the case, why are astronomy telescopes so wide?
  • It's not to get a narrow FOV -- you could get http://pan-starrs.ifa.hawaii.edu/public/home.html (http://pan-starrs.ifa.hawaii.edu/public/home.html) FOV using a 650mm lens on a 35mm system.
  • It's not resolution, you could just move the focal plane farther back to fit in more sensors -- eg 36cm could give you 1.7gigapixels with off the shelf components http://ambivalentengineer.blogspot.com.au/2012/08/argus-is.html (http://ambivalentengineer.blogspot.com.au/2012/08/argus-is.html)
  • It's because a wider aperture gives you more light = better low light performance




The original question was whether a crop camera with a given lens at f/2.8 performs the same as an equivalent focal length f/2.8 full frame. The answer is no, for equivalent focal lengths at the same f-stop the full frame sensor receives a lot more light and so gives less noise. In light of that, rs is right -- the lens might be nice for someone like me who only owns a crop camera but if you care terribly about low light performance then you should be on full frame.


Native sensor ISO? Let's not open *that* can of worms


Then it gets interesting when you look at the Metabones Speed Booster. I have to wonder if those kinds of abilities have been an option all along in crop sensor lens design.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Radiating on April 19, 2013, 11:34:01 PM
I can just imagine Canon & Nikon engineers staring at their screens in disbelief. Sigma engineers have managed to crack some code to lens making. I have the Sigma 35mm f/1.4, just tested the new Sigma 30mm f/1.4 and can't wait for this. Amazing lenses Sigma, now please give me a nice 50mm lens because I am not at all happy with my Canon 50mm. At least my Canon 85mm is great.

It's actually not difficult to make a lens like this any more than it is to make a 24-70mm f/2.8 lens for full frame.

Both will gather approximatly the same amount of light.

The amazing thing here is that Sigma has the motivation to make a lens like this. Canon have been sitting on their butts making ridiculous products for the recent past. T5i? WTF. 8-15mm L fisheye WTF?

Canon have dozens lenses that are 13 years old and a complete embarassment. I think Sigma just saw a moment of weakness and decided to obliterate the competition with these new products.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 04:39:37 AM
I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

(http://i758.photobucket.com/albums/xx229/trashcanalive/faq_zps34d1a6a5.png)

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: GaryJ on April 20, 2013, 06:49:07 AM
I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

(http://i758.photobucket.com/albums/xx229/trashcanalive/faq_zps34d1a6a5.png)
+1
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 08:20:57 AM
I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

(http://i758.photobucket.com/albums/xx229/trashcanalive/faq_zps34d1a6a5.png)
+1
Think of the metabones speed booster. Imagine now that they created one which made a FF lens create an imaging circle to match the APS-C crop sensor found in a Canon camera - a 1.6x telecompressor. That way you could mount, say, a 24-70/2.8 on crop with the metabones adapter, and get an identical FoV that the lens achieves on FF.

The 24-70/2.8 would be turned into a 15-44/1.75, right?

Now, we all know f1.75 is faster than f2.8. No-one is disputing that. If you mount this lens on the crop sensor camera with the telecompressor, it will allow for more than a stop faster shutter speeds at equal ISO's. It is an f1.75 lens, and no-one can argue with that. But where does this metabones get this extra speed from? Its not magic - its just it compresses the larger image circle into a smaller one - that extra light from that larger FF image circle is now condensed down into a smaller, more intense imaging circle, and is then received by a smaller sensor. However, in total its only the same amount of light/photons coming in through the lens which hits the sensor. The FF sensor and the APS-C sensor with a telecompressor both receive an identical number of photons, but the APS-C sensor has brighter light presented to it - more light per area - in other words its just over a stop brighter.

ISO's are rated to make exposure calculations work. What one camera does to achieve ISO 1600 isn't the same as another camera at ISO 1600 - especially with different size formats. The larger sensor as a whole has more photons hitting it at a particular aperture, so it needs to amplify the resulting electrical signal less for any given ISO. And even some cameras with the same sensor have to do different amplification, such as the Sony NEX 7 and Sony SLT A77.

If you can't see that, haven't you ever wondered why FF sensors are typically just over a stop better than crop sensors when it comes to noise? This faster aperture of the Sigma simply allows the noisier sensor to work at lower ISO's to finally fight back. Use a 18-35/1.8 at 35mm f1.8 1/100th of a sec ISO 10000 on crop, or a 24-70/2.8 at 56mm f2.8 1/100th, ISO 25600 on FF and you'll find its the same framing, depth of field, exposure and noise. (well, it would be if the Sigma was slightly brighter at f1.75)

Regardless of how you understand this difference between full frame and crop, and either agree or disagree with me, this Sigma lens really ups the game for crop users. From the specs point of view (and samples images), it looks great.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 09:55:53 AM
Think of the metabones speed booster. Imagine now that they created one which made a FF lens create an imaging circle to match the APS-C crop sensor found in a Canon camera - a 1.6x telecompressor. That way you could mount, say, a 24-70/2.8 on crop with the metabones adapter, and get an identical FoV that the lens achieves on FF.

The 24-70/2.8 would be turned into a 15-44/1.75, right?

Now, we all know f1.75 is faster than f2.8. No-one is disputing that. If you mount this lens on the crop sensor camera with the telecompressor, it will allow for more than a stop faster shutter speeds at equal ISO's. It is an f1.75 lens, and no-one can argue with that. But where does this metabones get this extra speed from? Its not magic - its just it compresses the larger image circle into a smaller one - that extra light from that larger FF image circle is now condensed down into a smaller, more intense imaging circle, and is then received by a smaller sensor. However, in total its only the same amount of light/photons coming in through the lens which hits the sensor. The FF sensor and the APS-C sensor with a telecompressor both receive an identical number of photons, but the APS-C sensor has brighter light presented to it - more light per area - in other words its just over a stop brighter.

I confess this the first time I've heard of a metabones speed booster but I get the idea and, yes, I'm with you so far.

ISO's are rated to make exposure calculations work. What one camera does to achieve ISO 1600 isn't the same as another camera at ISO 1600 - especially with different size formats. The larger sensor as a whole has more photons hitting it at a particular aperture, so it needs to amplify the resulting electrical signal less for any given ISO. And even some cameras with the same sensor have to do different amplification, such as the Sony NEX 7 and Sony SLT A77.

No, you've broken the sequence of logic from your metabones analogy. You can only say that the amount of light hitting the FF sensor is more because the FF sensor is bigger. The amount of light hitting each pixel is exactly the same, regardless of sensor size.

If you can't see that, haven't you ever wondered why FF sensors are typically just over a stop better than crop sensors when it comes to noise? This faster aperture of the Sigma simply allows the noisier sensor to work at lower ISO's to finally fight back. Use a 18-35/1.8 at 35mm f1.8 1/100th of a sec ISO 1000 on crop, or a 24-70/2.8 at 56mm f2.8 1/100th, ISO 1600 on FF and you'll find its the same framing, depth of field, exposure and noise. (well, it would be if the Sigma was slightly brighter at f1.75).
.

This is a compound error from the previous incorrect statement. Sensor size is not a factor in this.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 10:30:04 AM
This is a compound error from the previous incorrect statement. Sensor size is not a factor in this.
My original argument which has been hotly debated was merely that as nice as this Sigma 18-35/1.8 is on a crop camera, it's not quite as nice* as a 24-70/2.8 II is on a full frame camera.  I was comparing two complete systems, sensor and all. I know that a 24-70/2.8 is no match for this Sigma when they're both mounted on a crop body.

*by nice, I mean the 24-70 on FF goes wider, longer, is capable of a vaguely narrower DoF and capturing vaguely more light.

My argument is simply the total quantity of light a system can capture is more than just aperture - it is a combination of aperture and sensor size. The entrance pupil size when both systems have an equivalent FoV is a simple way of quantifying that.

But if you disagree with me and think that an f1.8 lens on 1.6x crop captures more light than a lens with an equal field of view at f2.8 on full frame, then fair enough. I've tried explaining this concept in many different ways, and you still don't get it. So I give up.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 20, 2013, 12:55:31 PM
But if you disagree with me and think that an f1.8 lens on 1.6x crop captures more light than a lens with an equal field of view at f2.8 on full frame, then fair enough. I've tried explaining this concept in many different ways, and you still don't get it. So I give up.

Why do you care how much light the lenses capture? That's irrelevant. What I care about is the final exposure.

With an f/1.8 lens, the final exposure will be brighter than with an f/2.8 lens no matter what (even if the f/2.8 lens is "capturing" more light, it doesn't "capture" enough to be brighter than the f/1.8 lens in-camera). This is true regardless of whether you use one lens on crop and one on FF, or both on FF, or both on crop.


Quote
My original argument which has been hotly debated was merely that as nice as this Sigma 18-35/1.8 is on a crop camera, it's not quite as nice* as a 24-70/2.8 II is on a full frame camera.

That is your subjective opinion. The fact of the matter is that the lenses will have their different uses and there will be situations where each lens is better than the other. Because the Sigma is an f/1.8 lens, it may be quite possible that the 24-70 does not create a bright enough exposure for a photographer in a low-light situation, so the Sigma will be much "nicer" to use in that situation.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 01:58:46 PM
Why do you care how much light the lenses capture? That's irrelevant. What I care about is the final exposure.

Because the Sigma is an f/1.8 lens, it may be quite possible that the 24-70 does not create a bright enough exposure for a photographer in a low-light situation, so the Sigma will be much "nicer" to use in that situation.

What about using the FF system at a higher ISO? As the FF sensors larger area allows it to capture 2.56x more light, you can use an ISO 2.56x higher (just over a stop), without suffering from any more noise than the crop sensor. ISO 10,000 on a typical APS-C sensor gives the same noise as ISO 25,600 on a typical FF. If you do choose to make use of the higher ISO's made available to you, the final exposure is the same, and the f1.8 crop system offers no low light advantage over an f2.8 full frame system.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 02:41:15 PM
What about using the FF system at a higher ISO? As the FF sensors larger area allows it to capture 2.56x more light, you can use an ISO 2.56x higher (just over a stop), without suffering from any more noise than the crop sensor.

You're trolling, surely.

ISO 10,000 on a typical APS-C sensor gives the same noise as ISO 25,600 on a typical FF. If you do choose to make use of the higher ISO's made available to you, the final exposure is the same, and the f1.8 crop system offers no low light advantage over an f2.8 full frame system.

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 02:46:46 PM
There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.
So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now :o

ps - it seems like you're slowing coming around to understanding my argument. Using that metabones analogy, you got the bit about how both the combined effect of aperture and image circle is equal to the total amount of light coming through the system. You now seem to get the other end of the argument - FF allows you to work at higher ISO's than crop. If you could just accept this missing part of the puzzle about it being the larger size of the sensor which allows you to work at these higher ISO's, I think you'll have it. Or are you going to start arguing about some other random part of the rationale?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: dirtcastle on April 20, 2013, 03:20:10 PM
What about depth of field? Is the depth of field always in a 1:1 relationship with the f-stop? In other words, will this lens get equivalent depths of field of an f/2.8 lens on a full-frame camera?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: LOALTD on April 20, 2013, 03:30:30 PM
I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

(http://i758.photobucket.com/albums/xx229/trashcanalive/faq_zps34d1a6a5.png)

+2

So much mis-information on this, nice work!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 04:35:04 PM
There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.
So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now :o

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.

ps - it seems like you're slowing coming around to understanding my argument. Using that metabones analogy, you got the bit about how both the combined effect of aperture and image circle is equal to the total amount of light coming through the system. You now seem to get the other end of the argument - FF allows you to work at higher ISO's than crop. If you could just accept this missing part of the puzzle about it being the larger size of the sensor which allows you to work at these higher ISO's, I think you'll have it. Or are you going to start arguing about some other random part of the rationale?

No, I'm content to stick with facts rather than come round to your argument.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 05:05:51 PM
There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.
So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now :o

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.
Print a whole FF image at 1m wide, the noise hides quite well. Now take a crop of that same image and print that crop at 1m wide, do you think the noise will be no less apparent?

You'd need to shoot the cropped image at a lower ISO to show an equivalent amount of noise in the final print.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 05:20:49 PM
There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.
So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now :o

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.
Print a whole FF image at 1m wide, the noise hides quite well. Now take a crop of that same image and print that crop at 1m wide, do you think the noise will be no less apparent?

You'd need to shoot the cropped image at a lower ISO to show an equivalent amount of noise in the final print.

OK, now I know you're trolling. You failed to quote the part of my post that answers this:

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: jemping on April 20, 2013, 06:13:30 PM
Not sure if anyone posted this already, but here is the website that has the sample images for this lens.

http://lcap.tistory.com/entry/Sigma-ART-18-35mm-f18-Preview (http://lcap.tistory.com/entry/Sigma-ART-18-35mm-f18-Preview)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 06:35:07 PM
OK, now I know you're trolling. You failed to quote the part of my post that answers this:

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.
So you agree that a larger enlargement makes noise more visible? If so, it seems like we're agreeing on this, but arguing about semantics.

From my point of view, amplification and magnification amount to one and the same thing. Take two different sized sensors with the same number of MP (1D X and 7D for example), then the smaller sensor clearly has smaller pixels. Each pixel receives less light, so in order to give the same electrical signal to create a calibrated ISO 100, it has to amplify to a greater level the smaller signal created from the smaller number of photons collected at its smaller pixel. However, take two sensors of different size with pixels of the same density (eg 1Ds mk III and 30D, or D800 and D7000), and on a pixel level, each pixel is the same size, so it collects the same number of photons, creates the same strength electrical signal and requires the same amount of amplification. But it is magnified less from that larger sensor (each pixel, together with its noise is a less significant part of the whole image), so it's noise has a lower effect on the whole image. Not all FF and crop comparisons fall into one of these two convenient categories, so it's usually a combination of amplification and magnification differences between the two. But one thing is for sure - take the whole image, and the bigger sensor will be less noisy. And all things being equal (same generation technology etc), you'll find the noise ratio is directly in line with the area ratio.

Similarly speaking, a 1.6x crop of FF is no different from a 1.6x crop sensor. The exposure doesn't differ with different sized sensors. The noise does. Bigger area to capture light equals more light captured. That equals lower noise. Or you can turn it around by bumping up the ISO and create the same noise with greater sensitivity. That is what makes an f2.8 lens on FF equal to an f1.75 lens on 1.6x crop.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 20, 2013, 07:49:18 PM
OK, now I know you're trolling. You failed to quote the part of my post that answers this:

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.
So you agree that a larger enlargement makes noise more visible? If so, it seems like we're agreeing on this, but arguing about semantics.

From my point of view, amplification and magnification amount to one and the same thing. Take two different sized sensors with the same number of MP (1D X and 7D for example), then the smaller sensor clearly has smaller pixels. Each pixel receives less light, so in order to give the same electrical signal to create a calibrated ISO 100, it has to amplify to a greater level the smaller signal created from the smaller number of photons collected at its smaller pixel. However, take two sensors of different size with pixels of the same density (eg 1Ds mk III and 30D, or D800 and D7000), and on a pixel level, each pixel is the same size, so it collects the same number of photons, creates the same strength electrical signal and requires the same amount of amplification. But it is magnified less from that larger sensor (each pixel, together with its noise is a less significant part of the whole image), so it's noise has a lower effect on the whole image. Not all FF and crop comparisons fall into one of these two convenient categories, so it's usually a combination of amplification and magnification differences between the two. But one thing is for sure - take the whole image, and the bigger sensor will be less noisy. And all things being equal (same generation technology etc), you'll find the noise ratio is directly in line with the area ratio.

Similarly speaking, a 1.6x crop of FF is no different from a 1.6x crop sensor. The exposure doesn't differ with different sized sensors. The noise does. Bigger area to capture light equals more light captured. That equals lower noise. Or you can turn it around by bumping up the ISO and create the same noise with greater sensitivity. That is what makes an f2.8 lens on FF equal to an f1.75 lens on 1.6x crop.

You were previously arguing that noise is directly related to the area of the sensor itself (i.e. APS-C needs 2.56x more signal amplification than FF) which is, of course, nonsense.

Are you still standing by the points below?

A FF sensor behind an f2.8 FF lens gathers 2.56x as much light as an f2.8 lens does on a 1.6x crop sensor due to the sensors 2.56x bigger surface area. If you only capture a fraction of all that FF f2.8 light by cropping it, well, the obvious happens from the light gathering point of view. The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating.

...surely you can see the 1.6x crop gives just over a stop less light gathering than a full frame sensor - making f1.8 on crop equal in light capturing terms to an aperture 1.6x smaller on FF - f2.88.

...to compare the 18-35/1.8 to the 24-70/2.8 on FF we'd need to set them both to a focal length to give an equal field of view. So for the sake of this example, lets use the long end of the Sigma's zoom - set the 18-35/1.8 to 35mm, which is equivalent of 56mm on the 24-70. We get the following:

56mm 1.0x [FF]      @ f/2.8 aperture = 20mm diam pupil
35mm 1.6x [APSC] @ f/1.8 aperture = 19.4mm diam pupil

So, vaguely less light gathering from the new Sigma lens, as well as a vaguely wider DoF.

Or think about it like this - imagine a photo taken with a FF lens and a FF sensor. Now you take that same photo and you crop out just the centre 40% - you've taken away 60% of the image - which is also 60% of the light that passed through that FF lens. You're left with only 40% of the light. That's what crop does. You need a faster lens on crop to make it capture the same amount of light in that smaller area.

...the 24-70 on FF goes wider, longer, is capable of a vaguely narrower DoF and capturing vaguely more light.

My argument is simply the total quantity of light a system can capture is more than just aperture - it is a combination of aperture and sensor size.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 20, 2013, 08:01:49 PM
Yes, I'm still standing by all of it. They're all different ways of putting across the exact same point. You quite clearly don't get it, so I'm out. Keep arguing this all you like, I'm done.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Radiating on April 20, 2013, 10:35:10 PM
Just wanted to chime in on the conversion debate.

A 15-35mm f/1.8 lens on crop, will deliver identical optical geometry to a 29-56mm f/2.88lens on full frame.

Depth of field for example, just like angle of view is a function of geometry.

(http://www.adelia.co.uk/wp-content/uploads/DOF-diagram.jpg)

So as the iris or aperture opens up more it allows more light in, but because that light is light that is coming at a higher incident angle it is focused over a greater area if it is behind or infront of the focal plane. So therefore you have a shallower depth of field. See how the red point is larger and therefore will be blurred on the open aperture example?

Here's another example:


(http://upload.wikimedia.org/wikipedia/commons/0/0c/Depth_of_field_illustration.svg)


People have been misled with crop to full frame conversions  for years.

The "35mm equivalent" is what is really important and nothing else. Your images on 35mm equivalent will always look the same no matter what.

From a physics perspective the "35mm equivalent" is capturing identical information. What really matters is the geometry of the light hitting the sensor, and with 35mm equivalent the geometry will always be the same for a given equivalence. Not only that but your flash settings etc will be identical:

Going back to the 35mm equivalent discussion, consider this:

On APS-C (like the 7D) compared to full frame (like the 5D Mark III)


The sensor is 1.6 x 1.6 times smaller.

35mm equivalent aperture - Multiply F-Number by (1.6 ) . (an f stop is a base 2 log, so even though we have 1.6x1.6 times as much light we take the square root, which is 1.6 to multiply the F number by. (example 2.8 x 1.6 = 4.48, 4.0 x 1.6 = 6.4, 1.8 x 1.6 = 2.88))

35mm equivalent focal length - Multiply by 1.6

35mm equivalent ISO or light sensitivity - Multiply by (1.6 x 1.6) (bet you haven't heard of that,  but if you do the math the an APS-C sensor amplifies the signal 1.6x1.6 times more at a given PIXEL than the a full frame camera, so even if both say ISO 800, ISO 800 on the an APS-C  it is multiplying the light from each individual pixel the same as ISO 2000 full frame, assuming they had identical resolution.

This is an important point of contention. So while for a given area of a light sensetive material, ISO provides a set level of amplification, cameras do not have a consistent area that they absorb incoming light on. Some have finger nail sized sesnors, and some postage stamp sized sensors. What's more important to consider is each individual pixel and it's level of amplification. Images are formed from pixels, so to acheive a true equivalency between different sized sensors and produce identical images we must consider the data collected at each individual pixel.

Simply put APS-C cameras have more dense sensors with more pixels, even with identical resolution. Because ISO is dependent on a given volume of light passing through a given area, if we increase the number of pixels in that area each pixel will have a stronger amplification level.

To illustrate this imagine a rain storm. On one part of the ground you have a set of square buckets that are 1" x 1" x 10", on another you have a set of buckets that are 2" x 2" x 10". After a given identical volume of rain, the 2x2x10 buckets will have 4 times more liquid in them than the 1x1x10 buckets. However four 1x1x10 buckets will have the same amount of rain in them as a single 2x2x10 bucket, as they will cover the same area (4 square inches).

Now lets imagine you have to create a given level of brightness from the amount of liquid in each bucket. Because the smaller buckets have a smaller cross section you have to multiply the amount of liquid in them for each smaller bucket to produce the same level of brightness as a larger bucket.

So on the 2x2x10 bucket, 20 cubic inches of rain might equal a luminance value of 128. For the same amount of rain fall each 1x1x10 bucket would only contain 5 cubic inches of rain, but if you wanted to have the same luminance value you would have to multiply the volume of light at each pixel by 4.

In this way, a sensor with denser pixels always has to multiply the volume of light to get a given luminance value more than a sensor that is less dense.

ISO is a function of the volume of light resulting in a certain exposure ie the amount of rain coming from the sky, resulting in a given exposure level. Say 5 inches of rain per hour resulting in a luminance value of 255, and 2.5 inches resulting in 128 in our example.

So to collect identical information ie number of photons at each individual pixel, with an APS-C and FF camera that have identical resolutions, we must use a different volumes of light hitting the sensor, specifically on APS-C we must have a higher volume of light, which results in a lower ISO to produce the same level of exposure. Just like we would have to use a greater flow of rain to collect the same amount of water in a smaller bucket compared to a bigger bucket.

Because light can simply be compressed and expanded at will by changing the beam path, which alters the volume of light in a given area (think magnifying glass), all that we have to do when converting an incoming image from FF to APS-C is focus the same image coming through an identical iris on a smaller area to capture the same exact information on an APS-C sensor as a full frame sensor. If you go through the geometry and the math of doing this equivalency something amazing happens though. At "35mm equivalent" ISO, focal length and aperture and the same shutter speed, on a full frame and APS-C sensor if you have a theoretically perfect body and lens system you would get the exact same photons which came from the exact same sources from your subject landing in the same number and location in each individual coresponding pixel site and resulting in the exact same luminance values in the output for both cameras. With each camera having a different ISO setting, focal length, and aperture.

Identical photons from identical sources, landing in coresponding pixels, resulting in identical luminance values are what is important when desiring to create identical images. That is how 35mm equivalence works, and why it is important.

Discussing anything other than 35mm equivalent values for cameras is like saying I have a million dollars, and then failing to mention these are Zimbabwe dollars worth $20 not, American dollars.

Yes aperture ISO and focal length are fixed numbers, but so are monetary figures, and the most important thing even the most basic dealing of currency has is WHAT currency you're dealing with, and 99% of people require an "equivalent" frame of refference to understand foreign currency or need to do a conversion. Likewise with cameras, geometry (type of currency) is the most important thing when dealing with the performance of a camera system, and the first thing anyone needs to do is bring up a conversion to the local frame of reference, APS-C ,35mm, whatever.

So in other words theoretically a Crop set to:

#1. 17mm - f/2.8 - ISO 800 - 1/50th - with 1/4 flash
#2. 55mm - f/2.8 - ISO 800 - 1/50th - with 1/2 flash

Will produce a 100% identical image with no difference in exposure, lighting, depth of field, field of view or composition when compared to a full frame set to:

#1. 27mm - f/4.48 - ISO 2048 - 1/50th - with 1/4 flash
#2. 88mm - f/4.48 - ISO 2048 - 1/50th - with 1/2 flash

Literally no difference.

Now of course each lens will have it's own characteristics and each body will likewise have it's own, and the full frame bodies and lenses tend to produce higher quality images due to the fact that miaturizing the system has adverse side effects, but if both bodies and lenses were theoretically perfect and had the same resolution these settings would deliver the exact same images with completely identical pixels.

Hope that cleared things up.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: RAKAMRAK on April 20, 2013, 11:32:42 PM
Very interesting and illuminating discussion. This is why I regularly read the forum. I can learn so much about photography and optics from those who have already learnt it.

But, regarding the new lens from from sigma my only questions are
1. Will it optics match the quality of it latest 35mm offering?
2. Can I afford it?

I hope the answers are yes to both these questions.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: CarlTN on April 21, 2013, 02:39:27 AM
AdamJ, rs, and Albi86, I admire your convictions on this subject.  It’s also impressive that a Sigma branded lens, has sparked so much discussion on a canon forum!

Radiating, that’s a nice chart.  I’m going cross-eyed looking at it, along with the long prose after.  Interesting points…thank you!
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Rienzphotoz on April 21, 2013, 04:44:33 AM
Very interesting and illuminating discussion. This is why I regularly read the forum. I can learn so much about photography and optics from those who have already learnt it.
+1
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 21, 2013, 05:10:26 AM
Going back to the 35mm equivalent discussion, consider this:

On APS-C (like the 7D) compared to full frame (like the 5D Mark III)

The sensor is 1.6 x 1.6 times smaller.

35mm equivalent aperture - Multiply F-Number by (1.6 ) . (an f stop is a base 2 log, so even though we have 1.6x1.6 times as much light we take the square root, which is 1.6 to multiply the F number by. (example 2.8 x 1.6 = 4.48, 4.0 x 1.6 = 6.4, 1.8 x 1.6 = 2.88))

You'll have to clarify what you mean by "35mm equivalent aperture." The fact is, f/1.8 is f/1.8 whether mounted on FF or crop.

35mm equivalent focal length - Multiply by 1.6

35mm equivalent ISO or light sensitivity - Multiply by (1.6 x 1.6) (bet you haven't heard of that,  but if you do the math the an APS-C sensor amplifies the signal 1.6x1.6 times more at a given PIXEL than the a full frame camera, so even if both say ISO 800, ISO 800 on the an APS-C  it is multiplying the light from each individual pixel the same as ISO 2000 full frame, assuming they had identical resolution, if resolution differs)

You're right, I haven't heard of that and the math eludes me. Please could you show it to us.


Edit: I reread your statement and saw that your calculation is "assuming they had identical resolution." So, in other words, the signal amplification of a sensor is related to pixel size, not sensor size. On that principle, we are agreed.

And on that same principle, the relationship of a lens's aperture to sensor size that has been made throughout this debate is spurious. It boils down to the same thing: small pixels are noisier than big pixels. If that is the only contention that this thread has been about, then we're all "in violent agreement."

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 21, 2013, 08:49:38 PM
Why do you care how much light the lenses capture? That's irrelevant. What I care about is the final exposure.

Because the Sigma is an f/1.8 lens, it may be quite possible that the 24-70 does not create a bright enough exposure for a photographer in a low-light situation, so the Sigma will be much "nicer" to use in that situation.

What about using the FF system at a higher ISO? As the FF sensors larger area allows it to capture 2.56x more light, you can use an ISO 2.56x higher (just over a stop), without suffering from any more noise than the crop sensor. ISO 10,000 on a typical APS-C sensor gives the same noise as ISO 25,600 on a typical FF. If you do choose to make use of the higher ISO's made available to you, the final exposure is the same, and the f1.8 crop system offers no low light advantage over an f2.8 full frame system.

You're right, the newest FF sensors typically deliver the same ISO as a crop sensor could with less noise. But when the next generation of crop sensors come out, the difference won't be as big. And let's not forget that crop bodies cost significantly less than FF bodies. Not everyone has the budget for an FF camera.

Also, not everyone has the latest FF sensor. What if you're shooting in a low-light situation with a 5D classic (the original mark I version) with a 24-70 f/2.8 and a Rebel T5i with the new Sigma 18-35 f/1.8? I would personally use the Rebel+Sigma in that situation.

I haven't seen any RAW samples of the T5i (and I'm actually not too familiar with the 5D's files either) but I'd guess that the noise performance gap between those two cameras isn't that huge.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 21, 2013, 09:06:39 PM
Or let me give you a different example:

Let's say Canon releases the new 70D with a next-generation crop sensor, and costs $1200 at launch. (Likely to happen if Canon wants the camera to compete with the Nikon D7100. Additionally, I believe the price would drop shortly after release, just like the 6D)
Now let's say this new sensor has noise performance as good as the 5D Mark II. (A stretch, but I think it's possible)
And let's pretend that the Sigma 18-35 f/1.8 costs $1200. (Honestly, I think it will cost a little less than this)

So now you've got your Canon 70D with Sigma 18-35 f/1.8 (which you paid $2400 for) and you shoot it at ISO 100, f/1.8, 1/200s.
Now you take your old 5D Mark II (which you bought used for $1200) and mount your 24-70 f/2.8 (the mark I version, which you also bought used for $1200) and shoot it at ISO 100, f/2.8, 1/200s.

Guess what? The crop image is going to be brighter than the FF image. And if the new, next-generation crop sensor really does have high-ISO noise performance as good as the 5D Mark II, then you also have a brand new crop setup that costs the same as a used FF setup and still gets a brighter exposure because of the large f/1.8 aperture than the f/2.8 on full frame, with the same noise at any ISO.

I would take that crop setup over that FF setup any day.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TrumpetPower! on April 22, 2013, 12:08:36 AM
Now let's say this new sensor has noise performance as good as the 5D Mark II.

Not a chance.

Cheers,

b&
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: 9VIII on April 22, 2013, 12:50:50 AM
Now let's say this new sensor has noise performance as good as the 5D Mark II.

Not a chance.

Cheers,

b&

Take a look at the Fujifilm X-E1. I don't know what kind of tricks they're pulling but it certainly looks like they have the noise beaten down, smothered, crushed and trampled 'till it's unrecognisable as whatever it used to be.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Rienzphotoz on April 22, 2013, 04:09:19 AM
Not sure if someone already posted this, but here is a Korean website that published images made with Sigma 18-35 f/1.8 lens mounted on a Canon EOS 600D
http://lcap.tistory.com/entry/Sigma-ART-18-35mm-f18-Preview (http://lcap.tistory.com/entry/Sigma-ART-18-35mm-f18-Preview)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 22, 2013, 05:53:00 AM
They also posted what it looks like when mounted to a full frame camera:

http://lcap.tistory.com/entry/Sigma-18-35mm-f18-with-5D-Mark-II (http://lcap.tistory.com/entry/Sigma-18-35mm-f18-with-5D-Mark-II)

Vignetting is not too bad at 35mm, so it's like getting a 35mm f/1.8 prime for FF that works at 18-34 on crop :P
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 22, 2013, 07:05:52 AM

So in other words theoretically a Crop set to:

#1. 17mm - f/2.8 - ISO 800 - 1/50th - with 1/4 flash
#2. 55mm - f/2.8 - ISO 800 - 1/50th - with 1/2 flash

Will produce a 100% identical image with no difference in exposure, lighting, depth of field, field of view or composition when compared to a full frame set to:

#1. 27mm - f/4.48 - ISO 2048 - 1/50th - with 1/4 flash
#2. 88mm - f/4.48 - ISO 2048 - 1/50th - with 1/2 flash



While I agree with you, I don't agree that framing (and DoF) and exposure always have to be considered together. The crop format is mature enough to be considered on its own and without always being compared to its 35mm equivalent.

It is plain that f/1.8 on crop corresponds to around f/2.8 on FF in terms of DoF. The point of the discussion is whether or not a f/1.8 lens will give you the same exposure both on crop and FF.

You calculation seems to agree with that, since the distance from f/2.8 to f/4.5 and from ISO 800 to 2048 is always (more or less) 1.3 EV.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TWI by Dustin Abbott on April 22, 2013, 09:42:46 AM
If nothing else, the new Sigmas are beautiful looking pieces of kit.  I love the look compared to the old "crinkle finish" design.  The new lenses are so clean and professional looking.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TWI by Dustin Abbott on April 22, 2013, 09:47:57 AM
The sample images at that site look pretty good.  Resolving power looks pretty impressive.  If I were a crop user I would be getting very interested about now.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 22, 2013, 12:34:43 PM
Regardless of all this arguing over APS-C vs FF noise, fact of the matter is this lens is not only  capable of doing f1.8 at 18mm, but it looks pretty good wide open based on those sample images. 

f1.8 is still f1.8 don't muddy the waters by bringing sensors into the picture
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: rs on April 22, 2013, 02:13:35 PM
I know I said I'm done, but just one quick last post from me on the subject. DPReview have a hands on preview of this lens up on their website, and on the first page they wrote this:

Quote from: dpreview
Sigma's choice of F1.8 as maximum aperture isn't a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What's more, it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that's just over twice as bright onto a sensor that's slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it's a major determinant of image quality. Essentially it means that APS-C shooters will be able to use lower ISOs when shooting wide open in low light and get similar levels of image noise, substantially negating one of the key advantages of switching to full frame.

http://www.dpreview.com/previews/sigma-18-35-1-8 (http://www.dpreview.com/previews/sigma-18-35-1-8)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 22, 2013, 02:17:56 PM
Yes, once again you're correct that the 1.8 crop lens has the same light-gathering ability as the 2.8 FF lens.

However, the important fact (to me, at least) is that the exposure from the 1.8 lens will be twice as bright-in camera than the 2.8 lens at the same ISO -- for low-light shooting this is more important to me than depth of field.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Albi86 on April 22, 2013, 02:28:49 PM
Yes, once again you're correct that the 1.8 crop lens has the same light-gathering ability as the 2.8 FF lens.

However, the important fact (to me, at least) is that the exposure from the 1.8 lens will be twice as bright-in camera than the 2.8 lens at the same ISO -- for low-light shooting this is more important to me than depth of field.

Which is what I also said. What matters is not the total amount of light, but the luminance on the sensor surface.

Do you understand the otherwise self-contradiction of saying that it gathers the same light but it delivers a twice as bright image....?
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 22, 2013, 03:15:27 PM
Right, the FF lens "gathers" twice as much light, and then spreads the "gathered" light over a much larger sensor. The crop lens "gathers" less light, but then focuses the light onto a small sensor, creating a brighter exposure than the full frame lens despite having "gathered" less actual light.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: TrumpetPower! on April 22, 2013, 03:29:32 PM
Right, the FF lens "gathers" twice as much light, and then spreads the "gathered" light over a much larger sensor. The crop lens "gathers" less light, but then focuses the light onto a small sensor, creating a brighter exposure than the full frame lens despite having "gathered" less actual light.

...but only when shot at an f/number sufficiently smaller such that the actual physical aperture is the same.

In other words, the APS-C camera shot with a 50mm lens at f/1.8 gathers the same amount of light as a 135 camera with an 80mm lens at f/2.8, and framing and depth of field and the rest are also comparable.

50 / 1.8 = 27.8
80 / 2.8 = 28.6

Cheers,

b&
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Kit. on April 22, 2013, 05:49:54 PM
I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

(http://i758.photobucket.com/albums/xx229/trashcanalive/faq_zps34d1a6a5.png)
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.
While it doesn't. We don't shoot sensors.
What really matters is the amount of light that is gathered from a square millimeter of the subject.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 22, 2013, 06:56:15 PM
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.

I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.

If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful and circuitous way of saying that APS-C sensors are, because of their typically smaller pixels, usually noisier than full-frame sensors - simple as that.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 22, 2013, 07:24:15 PM
Quote from: AdamJ

If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful and circuitous way of saying that APS-C sensors are, because of their typically smaller pixels, usually noisier than full-frame sensors - simple as that.


^^ THIS

And that FAQ table. All that needs to be said.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Kit. on April 22, 2013, 07:48:26 PM
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.
I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.
While you should be comparing pictures/scenes shot with both and then presented on comparable mediums (screen or paper).

Otherwise the comparison is meaningless.

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.
If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful
Just the opposite. The end result is about the same, because it is mostly limited by purely optical considerations. No matter what technical solutions are employed between the subject and the final image on paper or on monitor.

and circuitous way of saying that APS-C sensors are, because of their typically smaller pixels, usually noisier than full-frame sensors - simple as that.
Nope. They aren't noisier "because of their typically smaller pixels". Given the same size of the lens' entrance pupil (i.e. the same amount of light captured by the lens from an area on the subject), the same angle of view and enough of pixel well depth, they all will provide about the same amount of noise on the final medium.

They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Mantanuska on April 22, 2013, 09:13:07 PM


They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.

You still get more light from a smaller focal length (at the same pupil size) .  Thats why we describe the amount of light coming through the lens as a function of the focal length and pupil size, or in other words we use F-stop notation.

a 10mm aperture on an 18mm lens that gives a certain fov on APS-C lets in more light than a 10mm aperture on a  28mm lens that would produce the same fov on FF.

Thats why zoom lenses that aren't constant aperture get darker when you zoom in. The pupil isnt getting smaller, you just have less light entering the lens because you are constricting the FOV.

An F-stop is and F-stop regardless of format or focal length
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: wickidwombat on April 22, 2013, 09:19:08 PM
personally i see the f1.8 light gathering ability and effective wider depth of field as a benefit not a negative
the only issue is having a good high iso APS-C sensor to pair it with currently there isnt one in canons line
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: 9VIII on April 23, 2013, 12:47:07 AM
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.

I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.

If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful and circuitous way of saying that APS-C sensors are, because of their typically smaller pixels, usually noisier than full-frame sensors - simple as that.

Unfortunately I think that may actually still hold true.

http://www.geofflawrence.com/inverse_square_law.html (http://www.geofflawrence.com/inverse_square_law.html)

To get equivalence you need to account for the smaller surface area and the extra distance from the subject. Using a shorter focal length to make up for the tighter FOV effectively puts you farther away from the subject.


If someone would actually make a lens that gives the same FOV at the same focal length instead of throwing all the extra light away in FOV reduction, then we'd have an amazing short focal length lens. Right now wide angle on crop cameras just seems like a waste.

I do agree that everything would be better off with smaller pixels though, and that people should stop equating MP count with noise.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Kit. on April 23, 2013, 03:25:18 AM
They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.
You still get more light from a smaller focal length (at the same pupil size) .  That's why we describe the amount of light coming through the lens as a function of the focal length and pupil size, or in other words we use F-stop notation.

a 10mm aperture on an 18mm lens that gives a certain fov on APS-C lets in more light than a 10mm aperture on a  28mm lens that would produce the same fov on FF.
You don't get get more light from the subject at the same entrance pupil size. What you get is higher illuminated sensor, but you get it only because the same amount of light is concentrated on smaller sensor area. However, the shot noise on the image of an area of the subject is exactly the same, because the amount of photons originated from this area and reaching the sensor is exactly the same.

The amount of light the lens gathers through the same entrance pupil from the same solid angle of the scene is exactly the same no matter if the lens is going to focus this light on a 5 sq. micron pixel or on a 50 sq. micron pixel. As long as it's the same pixel on the output device, it will carry the same amount of shot noise.

Think about it.

Thats why zoom lenses that aren't constant aperture get darker when you zoom in. The pupil isnt getting smaller, you just have less light entering the lens because you are constricting the FOV.
But they are shooting different subjects!

There is even a more "ideal" object for comparison than zoom lenses. It's teleconverters. They increase the focal length keeping the entrance pupil constant. If you shot the same sporting event (i.e. the same shutter speed) with the wide open lens with and without a teleconverter ("push" the darker lens shots with higher sensor ISO) you will find the noise less apparent on a full frame of the shot without the teleconverter. But that's because you are shooting different subjects. Crop your non-TC shot to cover the same subject as your TC shot, convert both images to the same pixel count and see if the difference in the noise still exists.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 23, 2013, 03:45:23 PM
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.
I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.
While you should be comparing pictures/scenes shot with both and then presented on comparable mediums (screen or paper).

Otherwise the comparison is meaningless.

Which of those FAQs are you challenging?

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.
If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful
Just the opposite. The end result is about the same, because it is mostly limited by purely optical considerations. No matter what technical solutions are employed between the subject and the final image on paper or on monitor.

This doesn't advance the debate at hand.

and circuitous way of saying that APS-C sensors are, because of their typically smaller pixels, usually noisier than full-frame sensors - simple as that.
Nope. They aren't noisier "because of their typically smaller pixels". Given the same size of the lens' entrance pupil (i.e. the same amount of light captured by the lens from an area on the subject), the same angle of view and enough of pixel well depth, they all will provide about the same amount of noise on the final medium.

They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.

From my personal experience of 5D II vs 7D, that simply isn't the case.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Kit. on April 24, 2013, 04:07:15 PM
Nope, comparing shutter speeds of 70/2.8 to shutter speeds of 35/1.8 is not helping at all.
I didn't compare it specifically with 70mm, I compared it with a 24-70mm, because that was the comparison others made that started the debate.
While you should be comparing pictures/scenes shot with both and then presented on comparable mediums (screen or paper).

Otherwise the comparison is meaningless.

Which of those FAQs are you challenging?
Everything that relates to shutter speed.

Because it's not like people do (or at least should) pick their shutter speeds based on some fancy digits printed on their lenses. People should pick their shutter speeds based on the subject movements they need to freeze. If you cannot afford some part of the subject to move more than 5mm (in the subject plane) during the time of exposure, you will need to estimate the speed of this part (in mm/s) and divide it by 5 - then you will get (in 1/s) the lowest shutter speed you could afford to use in your shot, and then you will need to live with whatever amount of shot noise you are getting from the object get at this speed.

Now let's look how much noise we are actually getting. On our final image (printed or displayed on the monitor) we choose the smallest scale we need to resolve. It's historically - from the film era - called "circle of confusion" when reduced to length units in sensor plane; by at the moment we don't need it in length units, we need the solid angle that comprises this circle, the solid angle of the feature we need to resolve, the solid angle we need to get our photons from. And then the number of photons caught by this circle is the number of photons coming to our lens from that solid angle during the time of exposure - and then passing through the entrance pupil of our lens.

Then the absolute shot noise will be the square root of that number.
And the relative shot noise will be (absolute shot noise)-1.

See? No fancy digits printed on the lens. No sensor size. Even no sensor's pixel size. Only the subject (under the lighting), the desired end result and the absolute effective lens opening (in square millimeters or similar area units). Once you get this fixed, you know what noise you will get for your shutter speed, and you know what shutter speed corresponds to your noise.

Of course, you may want to boost your sensor's ISO to reduce the in-camera noise (and the right setting of ISO usually makes in-camera noise irrelevant when you need higher shutter speeds). But that's what you can afford to control. What you cannot afford to control is the amount of photons coming from your subject.

Actually, the same considerations also hold true for background blur, DoF and - in some sense - bokeh. All what you would ideally see on the final picture was already determined when the light coming from the subject crossed the (virtual) entrance pupil (the rendering of diaphragm visible through the front lens), then anything lying after the entrance pupil only added its distortions to it.

When you want to apply the same to bokeh, you will need to take into consideration the non-uniformity (and dependence on the distance) of the entrance pupil's transparency for out-of-focus objects. It's uniform for lenses with well-corrected spherical aberrations, darker in center (and lighter at the blades) for nearer objects in under-corrected lenses and for farther objects in over-corrected lenses, and lighter in center (and darker at the blades) otherwise.

For example, an unobscured bright dot at infinity will be rendered on the final picture exactly like the entrance pupil moved (without change of its physical size) into the subject's plane of focus in the direction of that dot. It will be flatly lighted for lenses with well-corrected spherical aberrations, nicely round for lenses with under-corrected spherical aberrations and doughnut-shaped for lenses with over-corrected spherical aberrations. Other than that, nothing should happen behind the entrance pupil in a good lens (of course, there could be ghosts and stuff if the lens is not so good). So, if your shoot with EF 50/1.4 wide open, a bright dot on your (far enough) background will be rendered as a flat octagon of ~36 mm (in subject's plane of focus) diameter, no matter what subject you shoot, no matter what your magnification is (well, if it's true macro, there could be exceptions), no matter what sensor size your camera has.

You seem to think that all that matters is the amount of light falling on a square micrometer of the sensor.
If you read the thread, you'll understand that my objective was to dispel the notion that f/1.8 on APS-C is in effect the same as f/2.8 on full frame. That notion is actually an unhelpful
Just the opposite. The end result is about the same, because it is mostly limited by purely optical considerations. No matter what technical solutions are employed between the subject and the final image on paper or on monitor.
This doesn't advance the debate at hand.
Well, I could not just go and say that most guides that teach photography by numbers do it in the wrong way (not that their numbers are wrong, but they just focus your attention on secondary details, letting you fail to see what really happens with the picture). I needed some pretext for that.

Those guides pay too much attention to what happens in the camera, although it's what happens outside the camera is what forms your images. The camera just adds its own technical limitations. These technical limitations were big enough during the "35mm film rolls" era, big enough to limit your thinking about your subject and about your end result. Those limitations weren't as big for sheet film, those limitations aren't as big for current large photo sensors, you can focus now on what happens outside the camera, paying only secondary attention on what happens inside.

They aren't noisier "because of their typically smaller pixels". Given the same size of the lens' entrance pupil (i.e. the same amount of light captured by the lens from an area on the subject), the same angle of view and enough of pixel well depth, they all will provide about the same amount of noise on the final medium.

They are noisier because the entrance pupils of their smaller lenses are generally smaller than on the lenses that provide the same angle of view for larger sensor formats. There are physical limitations in making large entrance pupils for smaller focal lengths, as pupils bigger than f/0.5 are impossible even theoretically.

From my personal experience of 5D II vs 7D, that simply isn't the case.
Maybe you did it wrong then.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: AdamJ on April 24, 2013, 06:13:55 PM
For willful obfuscation, you take the biscuit (and the competition has been intense).  ;D
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: indigo9 on April 25, 2013, 01:34:23 AM
For willful obfuscation, you take the biscuit (and the competition has been intense).  ;D

Whoah this is still going? A helpful reminder about what rs actually said initially:

..In other words ISO 10,000 on crop is pretty much equal to ISO 25,600 on FF in terms of noise. So feel free to shoot smaller apertures on FF and use higher ISO's to get the same light gathering and noise.
...
I see this Sigma lens as being a crop alternative to the 24-70 II on FF in just the same way as the 17-55 IS is a crop alternative to the 24-105L on F

Fixed the FAQ for you:

(http://www.levi.id.au/pics/fixedfaq.png)


The fact is, f/1.8 is f/1.8 whether mounted on FF or crop.

I think everyone agrees that you would use the same ISO on both cameras.

I think everyone agrees that if you were physically cutting up film then crop f/1.8 would be the same as full frame f/1.8.


In the real world though, digital crop sensors are not simply full frame sensors with the edges chopped off. Manufacturers keep the same photo resolution -- ie shrink the photosites -- at the expense of high ISO noise. For an identical production process and same resolution ISO 3200 FF is not the same as ISO 3200 crop: for cameras made within a few years of each other, crop will always be noisier.


So in low light situations, how would you get the same quality images on crop as full frame? First you'd lower the ISO. But then it would be underexposed -- so you'd either lower shutter speed (something that every camera can do and has nothing to do with the lens) or ... open the aperture, just like rs said at the very start.

f/1.8 is f/1.8 only if you think that image quality doesn't matter.





I approve of Radiating's summary:

So while for a given area of a light sensetive material, ISO provides a set level of amplification, cameras do not have a consistent area that they absorb incoming light on

...

Simply put APS-C cameras have more dense sensors with more pixels, even with identical resolution. Because ISO is dependent on a given volume of light passing through a given area, if we increase the number of pixels in that area each pixel will have a stronger amplification level.




Let's say Canon releases the new 70D with a next-generation crop sensor... Now let's say this new sensor has noise performance as good as the 5D Mark II. (A stretch, but I think it's possible)

A crop camera with better ISO performance than the same manufacturer's previous full frame? Show where this has ever happened in history.




It seems that AdamJ and Wildfire are semantically correct, but are deliberately ignoring what Kit, rs and I are all trying to say: you can't look at a lens in isolation.

Parallel:
50mm lens X has a resolution of 500 lp/mm, but the only camera you can put it on is a 640x480 VGA webcam.
50mm lens Y has a resolution of 50 lp/mm but will mount on a 5d3.

Which is a better lens?

Sure, you're semantically and theoretically correct to say the f/1.8 = f/1.8 but if you care about actual image quality then you can't ignore the sensor.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: thomeos on April 25, 2013, 04:53:14 AM
Hey folks, first post and hopefully something usefull.. :D

FYI:

A british shop just listed the lens for pre-order with a pricetag of GBP 999,- for both Nikon and Canon mount.

Don't let the URL fool you:
http://www.ukdigital.co.uk/sigma-30mm-f1-4-ex-dc-hsm-lens-canon-2966.html (http://www.ukdigital.co.uk/sigma-30mm-f1-4-ex-dc-hsm-lens-canon-2966.html)
http://www.ukdigital.co.uk/sigma-30mm-f1-4-ex-dc-hsm-lens-canon-2967.html (http://www.ukdigital.co.uk/sigma-30mm-f1-4-ex-dc-hsm-lens-canon-2967.html)

It seems my anticipated MSPR of 999 [regional currency] seems to become reality! :)

Cheers
Thomas
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Wildfire on April 26, 2013, 04:21:29 PM
Let's say Canon releases the new 70D with a next-generation crop sensor... Now let's say this new sensor has noise performance as good as the 5D Mark II. (A stretch, but I think it's possible)

A crop camera with better ISO performance than the same manufacturer's previous full frame? Show where this has ever happened in history.

You're right, it's never happened in history. But maybe it will soon. (Yes, that's a big maybe!).

I'd guess that the noise performance of the new Rebel SL1 can't be too much worse than the original 5D's. I think the 7D Mark II has a good chance of having excellent noise performance. It will never beat the latest full frame bodies, but maybe it can give the previous generation of FF cameras a run for their money.

And what about using Sigma's f/1.8 zoom on a full frame camera? Sure, it's not designed for FF, but from the Korean site with the samples it appears to mount and work properly on a 5D Mark II (though with heavy vignetting at all FLs below 28mm). If you're willing to lose resolution by cropping out the vignetting, then you actually can achieve FF-level noise performance with this lens, and still shoot at an f/1.8 exposure. (AND get the full f/1.8 depth of field as well!)

I'm not trying to say that crop will be better than FF -- it never will be. I just want to clarify for the people who may not know or understand the facts: at the same ISO/ shutter speed, an f/1.8 crop exposure is always brighter than an f/2.8 FF exposure.

If crop performance can approach FF performance at only a fraction of the cost, then that's good news for photographers everywhere. That's why this new lens is a big deal and that's why I want to get one. (I don't even own any crop cameras right now!)
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Pi on April 26, 2013, 06:24:45 PM

I think everyone agrees that you would use the same ISO on both cameras.

I do not.

Quote

f/1.8 is f/1.8 only if you think that image quality doesn't matter.

What is "f" in either case?



Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: indigo9 on April 27, 2013, 12:05:20 AM
Let's say Canon releases the new 70D with a next-generation crop sensor... Now let's say this new sensor has noise performance as good as the 5D Mark II. (A stretch, but I think it's possible)

A crop camera with better ISO performance than the same manufacturer's previous full frame? Show where this has ever happened in history.

You're right, it's never happened in history. But maybe it will soon. (Yes, that's a big maybe!).

I'd guess that the noise performance of the new Rebel SL1 can't be too much worse than the original 5D's.


Based on the fact that the 5D was slightly ahead of the 7D (which if I'm not mistaken is the same sensor as SL1 but different firmware and/or QC?) I would think you're right -- dxo says the 5D is slightly ahead but I've tried shooting the same shot with both in low light and it's pretty hard to pick which is better (once you can actually get the 5D to focus!).

I'm not trying to say that crop will be better than FF -- it never will be. I just want to clarify for the people who may not know or understand the facts: at the same ISO/ shutter speed, an f/1.8 crop exposure is always brighter than an f/2.8 FF exposure.

In fairness, I've assumed that if you were wanting wide apertures it was usually for low light shooting -- if you're shooting low ISO and just want short depth of field then it really doesn't matter (both approach the human SNR perception limit)



I think everyone agrees that you would use the same ISO on both cameras.

I do not.


I'm quite happy to be shown wrong, but was extrapolating from what would happen with physical film, where physically cropping film does nothing to ISO (in which case ISO would indeed be the same on both full frame and crop).

Unless I've misread https://www.google.com.au/search?q=ISSCC_ISO_BAER.pdf (https://www.google.com.au/search?q=ISSCC_ISO_BAER.pdf) then for digital cameras ISO speed is still based on sensor response to a given intensity of light, but simply uses a different measurement protocol.
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: Pi on April 27, 2013, 12:10:15 AM
I'm quite happy to be shown wrong, but was extrapolating from what would happen with physical film, where physically cropping film does nothing to ISO (in which case ISO would indeed be the same on both full frame and crop).

Cropping decreases the total light and increases the noise (because you enlarge).

The equivalent settings on FF requires the ISO to be multiplied by 2.56 (with the same QE anyway).
Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: indigo9 on April 27, 2013, 01:12:26 AM
I'm quite happy to be shown wrong, but was extrapolating from what would happen with physical film, where physically cropping film does nothing to ISO (in which case ISO would indeed be the same on both full frame and crop).

Cropping decreases the total light and increases the noise (because you enlarge).

The equivalent settings on FF requires the ISO to be multiplied by 2.56 (with the same QE anyway).

I think we're talking about something different.


What I was talking about is a scenario i just tested:

Full frame camera (5d)
- looking at a uniform white wall (possibly a cloudless sky is easier to make uniform?)
- 50mm EF lens
- f/4.0
- 1/30sec
- ISO for correct exposure is 1600

Same scene on an APSC camera (60d)
- looking at a uniform white wall
- 50mm EF lens [yes, it's cropped and not the same image -- that's why I specified a uniform wall]
- f/4.0
- 1/30sec
- ISO for correct exposure is still 1600. Histograms are virtually identical centered slightly above 50%. ISO 4000 is very much overexposed.

In this situation, a crop camera is the same as physically cropping film and the ISO is unchanged.

The fact that the total light reaching the crop sensor is less doesn't change the camera's ISO setting, the fact that less total light reaches the crop sensor changes the amplifiers to meet the ISO sensitivity definition.

Edit: changed the scenario settings to be real settings rather than hypothetical.

More amplification in the crop means more noise; when you say "equivalent settings" I assume you actually mean "equivalent settings to reach the same SNR"?

Title: Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C
Post by: thomeos on June 14, 2013, 01:13:20 AM
Now forget the boring stuff you guys go on and on about for weeks now and back to what matters:

BH Photo just mailed me that the Lens is now available for pre-order and its listed with just $799 which sounds almost too good to be true! :D
Oh and they claim availability by July 31st.

Also Sigma Poland had an MSPR online which seems to be gone again, being 3290 Zloty (=~779 EUR / ~1040 USD)

-edit-

Review by SLRGear:
http://slrgear.com/reviews/showproduct.php?product=1609 (http://slrgear.com/reviews/showproduct.php?product=1609)