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Gear Talk => Lenses => Topic started by: Marsu42 on January 30, 2013, 06:28:31 PM

Title: Please explain the need for f2.8 zooms
Post by: Marsu42 on January 30, 2013, 06:28:31 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Question: So according to this f2.8 is more important for available light and movement shots, but if that was case with the 5d2, I'm confused why still seems to be still valid with the 6d even though it's about 1 stop better ... either f2.8 was borderline in the past, or f2.8 - 1stop = f4 would be sufficient now - or am I missing something here?

Disclaimer: Please forgive slight traces of irony, this ia a real question because I don't entirely understand the issue, it's great people get whatever gear they like for any purpose they want.
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on January 30, 2013, 06:41:23 PM
Well, as Ziser said, f/4 or f/5.6 would be better since it gets more of your subject(s) in focus, and with a strobe you get plenty of light while stopping down further would make it harder to get any of your background in the image, it'd end up basically just being extremely sharp, or you'd see drastically more shadows from the strobe.

The thing to know about the 6D, is it's not really considered a 'professional' camera as such. Sure, it's a fine camera, but features and build quality is generally not up to 'pro'. Heck, Canon only calls the 1D-series as 'pro' cameras, everything else isn't.

When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance? Even though the center point AF sensor works fine with f/4 lenses, I believe it also has a double cross-point sensors there which are likely only available on an f/2.8 lens. Thus, you still get the point where your AF will likely be improved by having an f/2.8 lens, even if you take the shot at f/4 or f/5.6, even in available light.

The other factor is, if you could choose between f/2.8 or f/4, and the difference was ISO 3200 vs ISO 6400, which would you chose? If ISO 6400 is perfectly fine with you, go for it. If you want to drop down to ISO 3200, or increase your shutter speed while staying at ISO 6400, then you'd need to go for the f/2.8 lens.

There is also another thing that you may not think of, is that lenses wide open generally don't perform their best. I'm referring to resolution, CA, etc. f/2.8->f/4 can often make a difference for a lens, and f/2.8->f/5.6 can make a big difference. That's why the top end primes go to f/1.2-f/1.4. Sure, being able to shoot wide-open and get pretty good performance is great, but if you stop them down to f/2 or f/2.8, you get some really great performance while still being able to keep higher shutter speeds.
Title: Re: Please explain the need for f2.8 zooms
Post by: wickidwombat on January 30, 2013, 06:42:11 PM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

f2.8 gives much nicer shallow depth of field shots than f4 but probably both eyes will be in focus the one eye in focus thing is more the domain of fast primes

typically at weddings I'll either be shooting my 85 at f2 maybe f2.8 for more people in the shot and occassionally f4 or 5.6 but really i use this lens for portraits and couple shots
I use this lens more now than i do my 70-200 f2.8 since at f2 its sharper than even the 70-200 is at f2.8

I'll shoot the 70-200 at all sorts of apertures depending on the shot.
for the bride and groom walking down the isle its much better to stop down and play it safe
since using servo and how fast it all goes off there isn't alot of time to mess around and a redo isnt an option

the 16-35 i'll shoot at everything from f2.8 to f11 depending on the shot having 2.8 on this lens is a godsend with the 5Dmk3 for receptions (same goes for walking down the isle shots with this lens, stopped down is better) and its a fantastically fast focuser in low light, really really impressive on the 5Dmk3.

I'm looking forward to getting a sigma 35 f1.4 too and i just hope they come out locally soon before my next wedding shoot!
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on January 30, 2013, 07:02:39 PM
When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance?

My question is purely about sensor performance and why f2.8 will stay that important forever.

There is also another thing that you may not think of, is that lenses wide open generally don't perform their best.

... unless you're scraping together the money for a Canon 24-70L2

basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

Ok, thanks for the answer from a real world pro, so you're on the side that even f2.8 isn't really "fast" enough and it just happens so that the fastest zooms available are f2.8. So if I understand you correctly you'd rather go with a Tamron f2.8 + a faster prime like the Sigma 35mm than a Canon 24-70/f2.8 for the price of both combined?
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on January 30, 2013, 07:19:26 PM
When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance?

My question is purely about sensor performance and why f2.8 will stay that important forever.

There is also another thing that you may not think of, is that lenses wide open generally don't perform their best.

... unless you're scraping together the money for a Canon 24-70L2

basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

Ok, thanks for the answer from a real world pro, so you're on the side that even f2.8 isn't really "fast" enough and it just happens so that the fastest zooms available are f2.8. So if I understand you correctly you'd rather go with a Tamron f2.8 + a faster prime like the Sigma 35mm than a Canon 24-70/f2.8 for the price of both combined?

Well, even the Canon 24-70 v2 performs better stopped down. I never said that wide-open you can't get a lens that performs awesome. But if you stop down the Canon 24-70 v2 it gets even better.

That said, what lens(es) you chose often boils down to shooting styles, convenience (a high quality 24-70 is a lot easier to go 24, then 35, then 50 than changing primes), and can it get you what you want. Is it the best tool for the job, for what your budget can afford, and for how and what you are shooting.

Personally, while I wouldn't quite call myself a shooting pro, but I am shooting the residency for a small dance group, and while I'm renting the Tamron 24-70 for the next performance in a week, and probably buying that lens in the next 3-4 months. Not quite the weight of wickedwombat, or a couple of the other forum members, but I always seem to shoot in low or crazy lighting and I've found fast primes or f/2.8 zoom is practically a necessity. If you're shooting in decent lighting, or a studio or something, then ask if you really need a f/2.8 zoom. For me, I'm not shooting in those environments, so I've said yes, I do need a f/2.8 zoom (and the 70-200 some day, *sigh*).

Do you find yourself wide open all the time even as the ISO climbs higher and higher? Or are you comfortable going with a slower shutter and/or higher ISO and find an f/4 zoom is fine for you?
Title: Re: Please explain the need for f2.8 zooms
Post by: Chris Geiger on January 30, 2013, 07:22:27 PM
I normally shoot rings at around f11 and group shots at f4-f5.6 but the rest of the time I am normally at f2.8. I also have a couple primes that I use from time to time but most of my work is with the 24-70 and 70-200 f2.8 lenses. With the 5DIII I have plenty of ISO to shot at f4 most of the time, but I prefer the look at 2.8. I really wish I could get a 35-85 1.4 zoom. I'd pay some really big bucks for a lens like that.
Title: Re: Please explain the need for f2.8 zooms
Post by: RMC33 on January 30, 2013, 07:27:19 PM
From a sports perspective.

I own a Canon 16-35 f/2.8, 24-70 2.8, 70-200 MkII (FINALY sold my MK I), 200 f/2 and 400 f/2.8 MkII. Why? I need to keep a shutter speed in excess of 1/500 (pref 1/1000+) to stop action. Most of the areas I work in DOF is not an issue as much as stopping motion and making sure I get the shot hence the reason for "Fast glass". I don't use the 24-70 much in all honesty BUT it does come in VERY handy after the fact.

Example: Shot with a 70-200 f/2.8 MKI
1/640 f/5.6 ISO 200 with a circular polarizer. I have the ability to open up and get more light if I need if clouds come in or the sun starts to set.
Title: Re: Please explain the need for f2.8 zooms
Post by: wickidwombat on January 30, 2013, 07:30:37 PM
When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance?

My question is purely about sensor performance and why f2.8 will stay that important forever.

There is also another thing that you may not think of, is that lenses wide open generally don't perform their best.

... unless you're scraping together the money for a Canon 24-70L2

basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

Ok, thanks for the answer from a real world pro, so you're on the side that even f2.8 isn't really "fast" enough and it just happens so that the fastest zooms available are f2.8. So if I understand you correctly you'd rather go with a Tamron f2.8 + a faster prime like the Sigma 35mm than a Canon 24-70/f2.8 for the price of both combined?

only a part time pro ;)
unfortunately have to work a real job too :(

well I would happily pay $10,000 if canon made a 35-85 f2L IS that was razor sharp wide open
It would almost NEVER leave my 5Dmk3 and I could sell most of my primes
typically i'll shoot my 1.4 primes at f2 anyway as very often DoF at 1.4 is too thin however saying that if shooting an event in very low light with no flash even at iso 12800 i'll still be at f1.4 but really at those high iso
any sharpness differences between apertures are completely negated by the noise and loss of DR. In these situations there would be a real benefit of having f1.2 lenses

as for the tamron well I've had bad tamron encounters in the past so i'm really gun shy about this lens and have a somewhat prejudiced opinion which isnt helped when people report front elements falling out

Personally I think the 24-105L and say a sigma 35 f1.4 would be a more reliable combo
the 24-105L with some flash is a superb lens tough and very versitile and when f4 aint enough then swap over to the 35. If f4 isnt enough it doent take too much more light loss to make f2.8 not enough.
a neat trick with event photography is use a slower shutter speed to balance the ambient while keeping a decent iso like 1600 or even 3200 and using second curtain flash to freeze the subject these sort of techniques work great with f4 lenses (the IS on the lens helps reduce camera shake of the background and ambient while the flash takes care of the exposure and freezing the people. (look up dragging the shutter on google)

not to mention its basically impossible to take a good shot of half a dozen people at f1.4 either as only 1 person will have their nose in focus.

As with everything in photography the key is having a good understanding of the gear you are using, know its limits and work witin those limits. its only once you go beyond those limits that things get ugly

My wife however doesnt like shooting primes and so she prefers to use the 24-70L f2.8 mk1 over the primes

we are patiently waiting for the 24-70 f2.8L IS if it ever shows up or perhaps a sigma version to try out if that turns up
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on January 30, 2013, 07:44:55 PM
as for the tamron well I've had bad tamron encounters in the past so i'm really gun shy about this lens and have a somewhat prejudiced opinion which isnt helped when people report front elements falling out
I understand that and nearly forgot about the tamron until another CR wedding photog tested it and uses it as his wedding lens: http://www.canonrumors.com/forum/index.php?topic=11251.0 (http://www.canonrumors.com/forum/index.php?topic=11251.0)

The thing to know about the 6D, is it's not really considered a 'professional' camera as such.
... said photog now uses a 6d and praises it over his 5d2, sure a 5d3 is better (at €1000 more...) but the way I see it either the 5d2 and 6d are "professional" or neither is - except for the fact that the "budget" €2000 6d is only valid for cps silver in Europe, thanks, Canon.

Personally I think the 24-105L and say a sigma 35 f1.4 would be a more reliable combo
the 24-105L with some flash is a superb lens tough and very versitile and when f4 aint enough then swap over to the 35. If f4 isnt enough it doent take too much more light loss to make f2.8 not enough.
That's basically what I figured, too - but I don't have enough experience yet to be sure of that reasoning considering the very strong "everyone needs f2.8 zooms" opinions.

a neat trick with event photography is use a slower shutter speed to balance the ambient while keeping a decent iso
Thanks a lot for this and the other hints, it's just a pity the Canon cameras have such a slow x-sync (6d: 1/180s...), but I really have to test 2nd curtain sync more to get a feel how much it can make a bit of motion blur "snappier" and at what export resolution.
Title: Re: Please explain the need for f2.8 zooms
Post by: wickidwombat on January 30, 2013, 07:58:00 PM
Thanks a lot for this and the other hints, it's just a pity the Canon cameras have such a slow x-sync (6d: 1/180s...), but I really have to test 2nd curtain sync more to get a feel how much it can make a bit of motion blur "snappier" and at what export resolution.

x-sync is irrelevent when dragging the shutter since you are shooting at 1/10th second or so
2nd curtain sync basically fires the flash at the back of the exposure rather than the beginning
and so freezes the subject over the top of any blur that might have occured from movement
its a cool technique for dancing etc since it captures the motion in a more natural way than 1st curtain would
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on January 30, 2013, 07:58:52 PM
as for the tamron well I've had bad tamron encounters in the past so i'm really gun shy about this lens and have a somewhat prejudiced opinion which isnt helped when people report front elements falling out
I understand that and nearly forgot about the tamron until another CR wedding photog tested it and uses it as his wedding lens: http://www.canonrumors.com/forum/index.php?topic=11251.0 (http://www.canonrumors.com/forum/index.php?topic=11251.0)

The thing to know about the 6D, is it's not really considered a 'professional' camera as such.
... said photog now uses a 6d and praises it over his 5d2, sure a 5d3 is better (at €1000 more...) but the way I see it either the 5d2 and 6d are "professional" or neither is - except for the fact that the "budget" €2000 6d is only valid for cps silver in Europe, thanks, Canon.

Personally I think the 24-105L and say a sigma 35 f1.4 would be a more reliable combo
the 24-105L with some flash is a superb lens tough and very versitile and when f4 aint enough then swap over to the 35. If f4 isnt enough it doent take too much more light loss to make f2.8 not enough.
That's basically what I figured, too - but I don't have enough experience yet to be sure of that reasoning considering the very strong "everyone needs f2.8 zooms" opinions.

a neat trick with event photography is use a slower shutter speed to balance the ambient while keeping a decent iso
Thanks a lot for this and the other hints, it's just a pity the Canon cameras have such a slow x-sync (6d: 1/180s...), but I really have to test 2nd curtain sync more to get a feel how much it can make a bit of motion blur "snappier" and at what export resolution.

I'll second that the Tamron 24-70 f/2.8 VC is quite good. Maybe not quite up to the Canon 24-70 v2 in terms of sharpness and most build quality, but I can say from experience the build quality is definitely up there, and even wide open at ISO 6400 it was giving me quite good photos. Lighting for me was just horrendous though, probably worse than pretty much any wedding.
Title: Re: Please explain the need for f2.8 zooms
Post by: robbymack on January 30, 2013, 08:07:35 PM
It's all a trade off. Some like to shoot wide open with no flash and sacrifice dof, others like to shoot stopped down and add flash to maintain dof. Just comes down to preference. The f2.8 zooms will give you better af performance on some bodies so that is why they like them, plus the added versatility of a zoom vs several primes.
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on January 30, 2013, 08:14:29 PM
x-sync is irrelevent when dragging the shutter since you are shooting at 1/10th second or so

Wow, I really have to try that - but 1/10s does result in shots with a large motion trail that are rather "artistic", doesn't it? Or you could even pull a sample shot out of your stack :-) ?

I thought more of a 1/60s as the lower limit (and conveniently settable in the camera fw), and the upper x-sync limit with 2nd curtain was meant if for fast motion 1/500s+ would be more appropriate, but a lower shutter speed captures more ambient/background light at acceptable iso.
Title: Re: Please explain the need for f2.8 zooms
Post by: RS2021 on January 30, 2013, 08:19:05 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

I disagree with your basic presmise that  24-70 and 70-200 are "nailed" to wedding photographer's SLR's...and are "must-have" lenses. This is simply not accurate.

One wedding photographer I know uses his crop body and just two EF-S lenses and has a bag full of speedlights and radio gear ...he looks through my L lenses and smirks... "so, more toys I see?"  Another is an old timer who can pick his L-lenses from his oversized bag, but what sticks out in my mind is not his lens collection...but what he said about the amateurish need for razor thin DOF of f/1.2 on every occation...to paraphrase:

"You want a DOF where the bride appears to stand out amongst her guests, not so shallow a DOF that she apears to stand alone at her own party; it would be rather sad and a terrible waste of effort to have invited all those people!" (P.S. This gentleman also uses for the bride's portraits a softfocus prime 135 f/2.8!!!)

So it is almost a cliché to say that wedding photographers "must have" 24-70 f/2.8 or 70-200 IS II.  In fact, f/4 or higher would serve better at many moments.  For portraits and "beauty shots" probably faster lenses ranging in f/1.2 to f/2.8 work best, but a wedding is more than just portraits.

Many wedding photographers worth their salt and established in their business would have several speedlites well placed and programmed ahead of time across the hall and will also want some background DOF so it doesn't look like the couple is on their own. :)

Just my 2 cents.
Title: Re: Please explain the need for f2.8 zooms
Post by: Don Haines on January 30, 2013, 08:23:19 PM
I thought that 2.8 was important for using the high precision cross type auto focus sensors.... Better and more accurate focus at 2.8, then the pics shot at the aperture of choice... Correct me if I am wrong, but I thought that this was how the autofocus operates....
Title: Re: Please explain the need for f2.8 zooms
Post by: elflord on January 30, 2013, 08:55:04 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Saying that it's his "bread and butter setting" is different from saying that he uses it all the time.

Turning this around, what are the disadvantages of f/2.8 zooms ?

The main advantages are shallower dof (when needed,  not  necessarily on every shot) and that it helps AF performance
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on January 30, 2013, 09:21:07 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))
I disagree with your basic presmise that  24-70 and 70-200 are "nailed" to wedding photographer's SLR's...and are "must-have" lenses. This is simply not accurate.

Well, I actually I do agree with you and have to admit that this premise was an ironic part, 90% + 90% = 180% :-)

Another is an old timer who can pick his L-lenses from his oversized bag, but what sticks out in my mind is not his lens collection...

That's what a photog also said to me, but on the other hand the "I can shoot a wedding with my iPhone" photog type is a bit suspicious to me, too - I really can't tell what's reality and what's showing off in either "top gear" or "low gear" way.

I thought that 2.8 was important for using the high precision cross type auto focus sensors.... Better and more accurate focus at 2.8, then the pics append at the aperture of choice... Correct me if I am wrong, but I thought that this was how the autofocus operates....

Afaik: Yes and no. The 5d3/1dx-type af is more precise with the newest lenses (*not* necessarily the ones with the widest apertures, see lens groups in the manual), i.e. it can use all focus points, the doublecross sensor points don't degrade & the enhanced motor precision can be used (see lensrentals test on the 6d af which cannot). So that's +1 for the newest Canon f2.8 zooms.

On the other hand the camera *has* to focus more precisely when using a f2.8+ lens, and that can cost speed as a tradeoff for precision - so focusing with a "dumb" f4 lens might be faster since a little focus miss doesn't show.

And the 6d/5d2 is another matter, it has *no* cross-type af point @f2.8, but falls back to the less precise cross when the f2.8 line fails to focus - so -1 for f2.8 lenses since this af system is "anti-tuned" for it, there's a reason the Canon sample shots are made with the 17-40/4 and the kit lenses are 24-105/4 and the new 24-70/4.

Turning this around, what are the disadvantages of f/2.8 zooms ?

Um, price, bulk (scare-factor, pack-size) and weight come to mind :-p that's why I have a 70-300L and not a 70-200/2.8.
Title: Re: Please explain the need for f2.8 zooms
Post by: RMC33 on January 30, 2013, 09:26:15 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Saying that it's his "bread and butter setting" is different from saying that he uses it all the time.

Turning this around, what are the disadvantages of f/2.8 zooms ?

The main advantages are shallower dof (when needed,  not  necessarily on every shot) and that it helps AF performance

I would say the weight... but in retrospect I can now handhold my 200 f/2 for the duration of a 6 hour event now and have a 2nd body + lenses no problem now. Could not do that two seasons ago when I started.
Title: Re: Please explain the need for f2.8 zooms
Post by: spinworkxroy on January 30, 2013, 09:30:53 PM
Well, if you're shooting a wedding for a paying customer and with your reputation at stake, wouldn't you want to make sure you have the best of the best gears in the event you really need it?

The 24-70 and 70-200 are the best zooms in the market…and if you were to get the best, you'll get those.

Having an f2.8 zoom doesn't mean you'll shoot them at 2.8 all the time.. but it's there when you need it.

With flashes, maybe the f2.8 isn't that important..
BUT, there are many instances where flashes are NOT allowed, like in a church…that's where the 2.8 comes in handy…
Title: Re: Please explain the need for f2.8 zooms
Post by: srh on January 30, 2013, 09:31:48 PM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

Best thing I've read all day!  ;D
Title: Re: Please explain the need for f2.8 zooms
Post by: Passport on January 30, 2013, 09:44:24 PM
Faster lenses also allow you to see the image more clearly in the view finder.  You generally get better photos if you can see the composition.  The shallower depth of field enhances the distinction between what is in or out of focus making focus acquisition more precise.
Title: Re: Please explain the need for f2.8 zooms
Post by: Radiating on January 30, 2013, 10:03:12 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Question: So according to this f2.8 is more important for available light and movement shots, but if that was case with the 5d2, I'm confused why still seems to be still valid with the 6d even though it's about 1 stop better ... either f2.8 was borderline in the past, or f2.8 - 1stop = f4 would be sufficient now - or am I missing something here?

Disclaimer: Please forgive slight traces of irony, this ia a real question because I don't entirely understand the issue, it's great people get whatever gear they like for any purpose they want.

The minimum for capturing action on what I've found to be typical indoor light is:

1Ds Mark III/5D Mark II + f/2.8

OR

5D3/6D/1DX + F/4.0

The thing is that f/2.8 on a 5D Mark 3 gives you more flexibility, you aren't at the limit, so you're more comfortable.

The zoom range let's you frame shots better, and bokeh at f/2.8 is right at the boarderline between overpowering and pleasant.


So in the end f/2.8 on a newer full frame body is the optimum setup for getting a wide range of shots. Now shooting a f/2.8 lens at f/4.0 will often deliver sharper images than going with an f/4.0 lens to begin with so there is a disadvantage  to going f/4.0 to begin with, and you have less flexibility (as you don't have the option of f/2.8).

Going to an a prime that's faster than f/2.8 limits you because there is no zoom, you want SOME zoom if however small it is just so you can get framing right.
F/2.8 tends to be a good "all around" range. You have zoom, bokeh, and a comfortable amount of motion stopping without flash.


Personally I have a collection of the following lenses:

24-70mm f/2.8 II
24-105mm f/4.0 IS (for landscapes, still life and other times where IS helps more than f/2.8 because there is no motion to stop and for when I don't want the onion bokeh or focus shift of the 2.8 II)
70-200mm f/2.8 II

Sigma 35mm 1.4
Canon 50mm 1.4
Sigma 85mm 1.4


24mm TS-E + 1.4x TC & 2x TC  (35mm TS-E & 50mm TS-E)


Ideally I'm looking to pick up a Canon 200mm 2.0 too
Title: Re: Please explain the need for f2.8 zooms
Post by: RLPhoto on January 30, 2013, 10:14:07 PM
I love it when users say "it's only one stop" when comparing lenses. One stop is a lot! That's twice as good! Some users complain they couldn't tell the difference in rendering from faster glass and then complain that everyone one else can't see the difference.
Title: Re: Please explain the need for f2.8 zooms
Post by: Don Haines on January 30, 2013, 10:24:22 PM
Just get the f5.6 and f6.3 zooms.... welcome to the dark side......
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on January 30, 2013, 10:33:35 PM
Faster lenses also allow you to see the image more clearly in the view finder.  You generally get better photos if you can see the composition.  The shallower depth of field enhances the distinction between what is in or out of focus making focus acquisition more precise.

Not always, I believe the stock focusing screen (at least for the 5d3) is optimized to show up to f/2 or f/2.5, and anything faster you won't really see any difference.
Title: Re: Please explain the need for f2.8 zooms
Post by: verysimplejason on January 30, 2013, 11:13:16 PM
Anything faster is always welcome because of the availability of open-wide aperture for most low-light situations.  I think they're main disadvantage is that they're heavier and bulkier.  That's something you don't want to bear for 4-8 hours.  I think that's the main reason why primes are still very popular even if some zooms are quite as good or better than primes.  That and also the price.  If I'm not doing professional work, I prefer primes all day except for some very rare moments.  If I'm doing professional work, of course I want the fastest zoom I can afford.  This is because I want to get all possible pictures I can get at one time.  You don't want to miss some moments because you're changing lens or it's too dark for you to shoot.
Title: Re: Please explain the need for f2.8 zooms
Post by: agierke on January 30, 2013, 11:39:00 PM
i primarily shoot weddings (on the 5D2 and 5DC) and the reason i went with the 2.8 zooms was primarily that i found slower glass hunted for focus in low light far too often. i am still on version 1 for both the 24-70 and 70-200. the newer lenses coupled with the 5D3 might change the circumstances but i still wouldn't ever favor an F4 glass over an F2.8 or faster glass.

i rarely ever (probably never) shoot the 24-70mm at 2.8 because when i am using that lens i am typically trying to get more than one individual in the shot. 2.8 is too shallow a depth of field to get more than a couple people in focus so i am usually at an F5.6 or F4 (if i am desperate for light) on that lens. where i have seen the 24-105 hunt for focus at times in low light on the 5D series cameras, the 24-70 never hunts for focus for me. that is why i got it.

on the other hand, i will use the 70-200 at an f2.8 because with that focal length range i am typically trying to isolate a single individual. i prefer to use it an F4 because the results tend to be a bit sharper but i will push it to a 2.8 without much concern sometimes.

both those lenses are the foundation for the days shooting at a wedding for me....but, i would hesitate to call them my bread and butter. this past year i have added a 15mm fisheye, 35mm 1.4L, and 85mm 1.8 to the lenses that i bring on weddings. the fisheye i got just to get the occasional wacky overall shot (though i have found that lens to be extremely useful to me in my architectural shots...who knew!).

the 35mm F1.4 has really become my star performer for pre ceremony shots and couple shots. at F2.0 i find i can shoot a couple, keep them in the depth of field, and maintain really nice fall off to the background that i just dont get with the 24-70. a colleague of mine that i shoot with alot has quipped on several occasions that the 24-70mm is by far the most boring lens in her bag...and i tend to agree with her. but it covers alot of ground so for me it stays in the bag.

never been a fan of the F4 lenses. i always want the maximum versatility and to me not having the 2.8 is something i cant get past.

here is some stuff i shot (mostly as a 2nd) where the 24-70 and 70-200 is primarily featured:
http://www.adamgierkephotography.com/data/pssites/PS_37/Current_Wedding_Gallery/index_12.html (http://www.adamgierkephotography.com/data/pssites/PS_37/Current_Wedding_Gallery/index_12.html)

and here is some more recent stuff where i have started to incorporate the 35mm a bit more:

http://www.adamgierkephotography.com/data/pssites/PS_25/Wedding_Portfolio_12/index.html (http://www.adamgierkephotography.com/data/pssites/PS_25/Wedding_Portfolio_12/index.html)
Title: Re: Please explain the need for f2.8 zooms
Post by: Rocky on January 31, 2013, 01:42:08 AM
Even you do not need to shoot at 2.8, these are the benefits of having a 2.8 lens:
1. Brighter view finder image, so you can catch th expression easier.
2. Faster focusing in dim light
3. More accurate focus after you have stopped downth lens during exposure due to increased DOF.
4. Sharper image after stopped down the len. Usually, a 2.8 lens at 4.0 is sharper than a lens wide opened at 4.0
Draw back of 2.8 lens:
1. Size and weight.
2. $$$
Title: Re: Please explain the need for f2.8 zooms
Post by: ewg963 on January 31, 2013, 04:06:20 AM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P

f2.8 gives much nicer shallow depth of field shots than f4 but probably both eyes will be in focus the one eye in focus thing is more the domain of fast primes

typically at weddings I'll either be shooting my 85 at f2 maybe f2.8 for more people in the shot and occassionally f4 or 5.6 but really i use this lens for portraits and couple shots
I use this lens more now than i do my 70-200 f2.8 since at f2 its sharper than even the 70-200 is at f2.8

I'll shoot the 70-200 at all sorts of apertures depending on the shot.
for the bride and groom walking down the isle its much better to stop down and play it safe
since using servo and how fast it all goes off there isn't alot of time to mess around and a redo isnt an option

the 16-35 i'll shoot at everything from f2.8 to f11 depending on the shot having 2.8 on this lens is a godsend with the 5Dmk3 for receptions (same goes for walking down the isle shots with this lens, stopped down is better) and its a fantastically fast focuser in low light, really really impressive on the 5Dmk3.
+1
Title: Re: Please explain the need for f2.8 zooms
Post by: Hillsilly on January 31, 2013, 04:34:59 AM
Hardly a pro, and a lot of the time I take group photos I often wish I had used a smaller aperture for increased DOF.  So I see where the OP is coming from.  But when I look at a good set of wedding photos, the photographer will generally have a good selection of narrow depth of field photos.  These would tend to be the less formal shots and are often the best / favourite photos of the day.  (Although, many of these are probably taken with a prime with an even wider aperture than f/2.8).
Title: Re: Please explain the need for f2.8 zooms
Post by: tomscott on January 31, 2013, 06:14:06 AM
I think this is where the amateur and pro argument reaches its peak.

If you are a pro, shooting and making money then gear is a tool, any advantage is a plus. The gear pays for itself whereas an amateur may struggle to justify the purchase. Which is fair. But these zooms are there to guarantee results. Similar to ISO 'better being noisy than missing or getting blurry shots' your better having a smaller DOF than missing the shot entirely.

F2.8 lenses are there for those occasions where you cant use flash, or your in a large room where flash just isnt enough. F2.8 has saved me many a time, also if you are shooting slightly wider you can still get sharp results at F2.8 across a frame, at closer distances the DOF seclusion is more apparent, granted softer but it can be used in those 5% scenarios. Also helps the cameras AF.

If you choose F4 then your advantage is F4 thats it. I know for a fact that when shooting say the first dance at a wedding, using F4-5.6 with flash is still hard even at ISO3200.

But on the other hand, using a 24-105mm with a prime can work really well, it depends on the situation and the light. F4 on the 24-105 gives nice results on a FF camera. The zoom just gives you more scope, instead of worrying about changing lenses. As a wedding photographer using two cameras is a good idea, one with a wider lens (zoom or prime) one with a tele.

TBH a 50mm will have you covered for most of the day at a wedding, so is it necessary? No, but it is nice to know you can IF you need too. Using a zoom can make you lazy with a prime you just have to move around more to find the shot. But you could argue you are more likely to loose the shot.

There are many arguments, it depends on how you like to work and your budget.

Title: Re: Please explain the need for f2.8 zooms
Post by: bycostello on January 31, 2013, 06:36:07 AM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P




 ;D ;D ;D ;D ;D ;D
Title: Re: Please explain the need for f2.8 zooms
Post by: bycostello on January 31, 2013, 06:37:45 AM
an f2.8 lens will be sharper at f4 where an f4 lens would be sharper at f5.6 or so...  a jag will go 150 mph but at 70 it hums along beautifully if you get the analogy...
Title: Re: Please explain the need for f2.8 zooms
Post by: pakosouthpark on January 31, 2013, 07:08:41 AM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P




just brilliant!!
Title: Re: Please explain the need for f2.8 zooms
Post by: spinworkxroy on January 31, 2013, 07:31:39 AM
basically having a wide aperture available is like a condom
its better to have it and not need it than to need it and not have it :P



I hear it feels better without :) so does that mean not having an f2.8 lens feels better too?


just brilliant!!

Title: Re: Please explain the need for f2.8 zooms
Post by: Maui5150 on January 31, 2013, 07:38:26 AM
My experience has been they are over all:

-- Faster
-- Sharper

I shoot a 2.8 version versus an F/4 version at say 4 or 5.6, I notice better AF and better over all quality on the shots on the 2.8 version.  I think with most zoom lenses, they have most of their issues at the end so a F/4 lens may be fairly equal to the 2.8 at say F/8 or F/11, but more wide open, especially at F/4 the 2.8 has always out performed in my experience. 

In many case, I find the build and over all range of the lens to be better.  This may be subjective, but in a similar example in the 50s, is the 1.2 really that much better than the 1.4 and the 1.8. 

Yeah.  It is.  Granted, it is an L versus non L as well, but I noticed a huge difference stepping up from the 70-200 F/4 to F/2.8, especially in speed.  Some may argue the price, and the F/4 is a solid performer, but when it comes down to it, with almost anything in life, if your desired range is at the edge of a products capability, you are often better off finding the product that slightly to moderately exceeds your need. 
Title: Re: Please explain the need for f2.8 zooms
Post by: Studio1930 on January 31, 2013, 09:23:53 AM
One thing that has not been directly mentioned is that a good photographer will envision the amount of DOF he/she wants in a shot and then adjust the aperture to match based on the focal length of the lens, the distance to the subject and the distance from the subject to the background.  As the distance variables change, so must your aperture to keep the same DOF.

My point is that sometimes you might need f/4 and sometimes you might back up and need f/2.8 to get that same DOF.   You can't do that with an f/4 only lens.  With a slower lens (and/or crop body) you will find yourself needing to get closer to your subject to get a narrow DOF which may have you cropping them more than you wanted.  If shallow DOF shot at a distance is not what you want then a slower lens might work but at some point most professionals want that shallow DOF which slower lenses when shot at a distance (for full length for example) may not provide.

Full length shot with shallow DOF:
(http://photos.modelmayhem.com/photos/091021/18/4adfb1db2acdb.jpg)
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on February 01, 2013, 08:29:50 AM
One thing that has not been directly mentioned is that a good photographer will envision the amount of DOF he/she wants in a shot and then adjust the aperture to match based on the focal length of the lens, the distance to the subject and the distance from the subject to the background.  As the distance variables change, so must your aperture to keep the same DOF

Thanks, I didn't think about this point, keeping a consistent dof across the lens zoom capabilty certainly is a plus for a professional appeal.

Also a big thank you to all posters explaining the pro and cons to me w/o any "just get the best" attitude, to summarize my current understanding f2.8 zooms are for

* keeping a constant dof
* pro-looking bokeh
* faster shutter speed for fast motion with zoom
* reserve in available light situations, though as far as noise goes 5d2+f2.8 = 6d+f4
* sharpness because f2.8 lens stopped down > f4 lens wide open
* more reliable af  - though I wonder if this is valid for the 5d2/6d af? Anyone?

All these points make me tend to get a Tamron 24-70 lens for the 6d after all since my lenses don't pay for themselves by pro shooting, I will shoot somewhat stopped down often and 100% crop sharpness is nice to have, but not critical to me... and the plain matter of the fact is that I could get 2 (two) 6d+24-70vc for 1 (one) 5d3+24-70ii :-o
Title: Re: Please explain the need for f2.8 zooms
Post by: enice128 on February 01, 2013, 10:16:01 AM
My experience has been they are over all:

-- Faster
-- Sharper

I shoot a 2.8 version versus an F/4 version at say 4 or 5.6, I notice better AF and better over all quality on the shots on the 2.8 version.  I think with most zoom lenses, they have most of their issues at the end so a F/4 lens may be fairly equal to the 2.8 at say F/8 or F/11, but more wide open, especially at F/4 the 2.8 has always out performed in my experience. 

In many case, I find the build and over all range of the lens to be better.  This may be subjective, but in a similar example in the 50s, is the 1.2 really that much better than the 1.4 and the 1.8. 

Yeah.  It is.  Granted, it is an L versus non L as well, but I noticed a huge difference stepping up from the 70-200 F/4 to F/2.8, especially in speed.  Some may argue the price, and the F/4 is a solid performer, but when it comes down to it, with almost anything in life, if your desired range is at the edge of a products capability, you are often better off finding the product that slightly to moderately exceeds your need.
This is my main argument & reason on why I'm actually going today to upgrade to the 16-35II from my 17-40. A 2.8 aperture is so important for me. I do some small weddings, sweet 16s as well as other events using my 17-40 for over a year now but I feel it's not enough. I love using my 50 1.2 & 70-200 2.8 at these events but my 16-35 will now take the 17-40's place as my main lens. U cannot beat the the overall quality of 2.8 & I absolutely love the look of 2.8 with its DOF!
Title: Re: Please explain the need for f2.8 zooms
Post by: bdunbar79 on February 01, 2013, 11:47:24 AM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Question: So according to this f2.8 is more important for available light and movement shots, but if that was case with the 5d2, I'm confused why still seems to be still valid with the 6d even though it's about 1 stop better ... either f2.8 was borderline in the past, or f2.8 - 1stop = f4 would be sufficient now - or am I missing something here?

Disclaimer: Please forgive slight traces of irony, this ia a real question because I don't entirely understand the issue, it's great people get whatever gear they like for any purpose they want.

f/2.8 zooms are absolutely essential in low-light situations with fast-moving, or moving subjects.  I don't know of any other pro sports photog who doesn't use an f/2.8 zoom lens.  There are those who argue for primes in indoor sports, but you get less shots and less angles and interesting ones.  I have way more keepers and action with the zoom vs. the prime.  f/2.8 is a whole stop better than f/4 and yes, that makes a HUGE difference.
Title: Re: Please explain the need for f2.8 zooms
Post by: Studio1930 on February 01, 2013, 12:10:18 PM
The standard lens requirement for shooting events/weddings seem to be a combination of 24-70/28 and 70-200/2.8, I read both are nailed to a pro's camera 90% of the time (though I have problems doing the maths :-))

A lens with a larger aperture afaik has three advantages: better af on some bodies, better subject isolation/creativity (just one eye in focus) and last not least a "fast" lens is required for "low light" shots.

My question rose when I read the great book "Captured by the Light" by David Ziser who - believe it or not - writes that f4 to f5.6 (for convenience or added safety) is his bread and butter setting for posed candid wedding flash shots, and he used the 5d2 at that time.

Question: So according to this f2.8 is more important for available light and movement shots, but if that was case with the 5d2, I'm confused why still seems to be still valid with the 6d even though it's about 1 stop better ... either f2.8 was borderline in the past, or f2.8 - 1stop = f4 would be sufficient now - or am I missing something here?

Disclaimer: Please forgive slight traces of irony, this ia a real question because I don't entirely understand the issue, it's great people get whatever gear they like for any purpose they want.

There are those who argue for primes in indoor sports, but you get less shots and less angles and interesting ones.  I have way more keepers and action with the zoom vs. the prime.

Sometimes you have such low light that a faster prime like the 200 f/2 or the 135 f/2 is the only way to capture it at acceptable ISO levels.  Also the 200 f/2 focuses faster in low light but this doesn't apply to the original argument about having a constant aperture since it isn't a zoom. :)

200 f/2 in very low light.

with a 1DX
(http://studio1930.com/photocart/photos/12-dog_agility/16-akc/10230-akc_-_carthage_10-26-2012/sat_oct_27_-_ex_std/zm_1e92C5D0_20121027S1930-0204.JPG)

with a 1D4
Mercury Vapor lights uncorrected:
(http://studio1930.com/photocart/photos/12-dog_agility/16-akc/10072-gkc_dog_training_club_-_4!21!2012/1/zm_a3E2Ea46_20120421S1930-486.JPG)
Title: Re: Please explain the need for f2.8 zooms
Post by: TrumpetPower! on February 01, 2013, 12:20:22 PM
I love it when users say "it's only one stop" when comparing lenses. One stop is a lot! That's twice as good! Some users complain they couldn't tell the difference in rendering from faster glass and then complain that everyone one else can't see the difference.

You keep harping on this "one stop is twice as much," without seeming to realize that, though technically true, there's a very good reason why we use a logarithmic scale for exposure.

In this context, a linear scale is useless. One stop is not, in fact, "twice as good." One stop is basically one zone on the Adams scale. And, while, yes, it's important to place midtones in zone V instead of zone IV or zone VI, it's not exactly a huge deal to move exposures around by a single stop.

By the time you get to two stops, things change. The difference between zone III and zone V or zone V and zone VII is the difference between midtones and shadows or highlights with good detail. But just a single stop? That's your wiggle room, what you have to work with for interpretation, your margin for error.

Cheers,

b&
Title: Re: Please explain the need for f2.8 zooms
Post by: bdunbar79 on February 01, 2013, 12:22:40 PM
Studio,

I don't disagree with you at all.  I'm shooting in a gym tonight that I can't use f/2.8, I have to use f/2 or f/2.2 to keep it at 1/500, ISO 5000.  So I have to use the 135L.  Better to have legs cut off vs. no photo at all :).
Title: Re: Please explain the need for f2.8 zooms
Post by: The_Arsonist on February 01, 2013, 02:09:15 PM
I love it when users say "it's only one stop" when comparing lenses. One stop is a lot! That's twice as good! Some users complain they couldn't tell the difference in rendering from faster glass and then complain that everyone one else can't see the difference.

You keep harping on this "one stop is twice as much," without seeming to realize that, though technically true, there's a very good reason why we use a logarithmic scale for exposure.

In this context, a linear scale is useless. One stop is not, in fact, "twice as good." One stop is basically one zone on the Adams scale. And, while, yes, it's important to place midtones in zone V instead of zone IV or zone VI, it's not exactly a huge deal to move exposures around by a single stop.

By the time you get to two stops, things change. The difference between zone III and zone V or zone V and zone VII is the difference between midtones and shadows or highlights with good detail. But just a single stop? That's your wiggle room, what you have to work with for interpretation, your margin for error.

Cheers,

b&

Ah, but what if you have to under expose to get the shutter speed fast enough for indoor sports. If one stop is the adjustment curve, and I have to under expose by one stop to get the shot, then there's my wiggle room. I need a 2.8 to get within one stop of my final exposure for indoor basketball. I also use primes, but to get the right moment when someone is driving down the court toward me, I need the zoom.
Title: Re: Please explain the need for f2.8 zooms
Post by: Studio1930 on February 01, 2013, 02:15:11 PM
Studio,

I don't disagree with you at all.  I'm shooting in a gym tonight that I can't use f/2.8, I have to use f/2 or f/2.2 to keep it at 1/500, ISO 5000.  So I have to use the 135L.  Better to have legs cut off vs. no photo at all :).

Yep, I thought you would since I have seen what you shoot and know you often need faster glass that a zoom can't provide. :)  I thought I would mention it so others would see that there are times that you just need a faster prime (even though we have diverged from the main point a bit).

As to the poster above (TrumpetPower!) about the 1 stop and the zone info..  1 stop is 1 stop.  You aren't going to shoot an image that has all of its info in just one zone so someplace in your image is probably going to be all of the zones which mean you are going to see the difference from zone 3 to zone 4.  Maybe you personally don't see the difference in 1 stop, but I would argue that most people can take an average image and click one more stop of exposure and see the difference quite well.

Here is one stop of exposure difference...
(http://studio1930.com/image_share/s1930/zm_1e92C5D0_20121027S1930-0204.JPG)
(http://studio1930.com/image_share/s1930/zm_1e92C5D0_20121027S1930-0204a.JPG)
Title: Re: Please explain the need for f2.8 zooms
Post by: Nicophotographic on February 01, 2013, 06:09:26 PM
I see where you are coming from with the irony. There is a lot of issues and opinions with aperture. Your views are correct. This is how i see it and my experience of togging....generally the sweet-spot area for most lens are when they are stopped down a couple or three stops.  Please note my comments are general and this will depend on all sorts of variables, light, composition, distance etc etc. If you have a lens that has variable f say 4.5-6.3 then you will be stopping it down to say f8-f11. Ok alls well and good in good light or stability like on a bean bag or tripod. Obviously stopped down to f16 etc for landscape and on a tripod. However when shooting on the move or moving subjects then f2.8 or less is a must. I use a 70-200II IS F2.8 and from a fast moving vehicle for stills or video are perfect. I could go on but will not become too boring. Hope this helps.
Title: Re: Please explain the need for f2.8 zooms
Post by: TrumpetPower! on February 01, 2013, 09:09:29 PM
As to the poster above (TrumpetPower!) about the 1 stop and the zone info..  1 stop is 1 stop.  You aren't going to shoot an image that has all of its info in just one zone so someplace in your image is probably going to be all of the zones which mean you are going to see the difference from zone 3 to zone 4.  Maybe you personally don't see the difference in 1 stop, but I would argue that most people can take an average image and click one more stop of exposure and see the difference quite well.

Look, I'm not trying to claim that there's no difference at all between two images shot one stop apart. Of course there is. I'm just pointing out that the difference is minor, and well within the normal range of typical exposure adjustments. Indeed, all modern camera meters are configured to underexpose by at least a stop (if not two) and a corresponding stop (or two) of digital push is by default applied to the raw development. This is a good thing, generally, as there's so little headroom that highlights would regularly get blown otherwise.

I'm attaching five side-by-side shots from a bracket, each shot one stop apart. I've normalized them all to the same exposure. This is with a 5DIII and a TS-E 24 II, ISO 100 and f/5.6; shutter ranges from 1/4 on the left to 1/60 on the right. The one on the left has some reconstructed highlights; the shadows on the right are a bit ugly. Oh -- and the one on the left has a proper exposure as far as the sensor is concerned and the one next to it is exposed according to the camera's meter.

Now, if I hadn't told you the details, would you be able to tell the difference?

I'm also attaching the final edit, which I did by not normalizing the exposures and masking some of them on top of each other.

Cheers,

b&
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on February 01, 2013, 09:12:52 PM
As to the poster above (TrumpetPower!) about the 1 stop and the zone info..  1 stop is 1 stop.  You aren't going to shoot an image that has all of its info in just one zone so someplace in your image is probably going to be all of the zones which mean you are going to see the difference from zone 3 to zone 4.  Maybe you personally don't see the difference in 1 stop, but I would argue that most people can take an average image and click one more stop of exposure and see the difference quite well.

Look, I'm not trying to claim that there's no difference at all between two images shot one stop apart. Of course there is. I'm just pointing out that the difference is minor, and well within the normal range of typical exposure adjustments. Indeed, all modern camera meters are configured to underexpose by at least a stop (if not two) and a corresponding stop (or two) of digital push is by default applied to the raw development. This is a good thing, generally, as there's so little headroom that highlights would regularly get blown otherwise.


Huh? I have never heard that the in camera meters underexpose, and then do a digital push. I know that different camera makers have different amount of eV's per 'bin' of bits in each channel. Anyone who knows more care to chime in to confirm or deny? Neuro?
Title: Re: Please explain the need for f2.8 zooms
Post by: TrumpetPower! on February 01, 2013, 09:15:53 PM
Huh? I have never heard that the in camera meters underexpose, and then do a digital push. I know that different camera makers have different amount of eV's per 'bin' of bits in each channel. Anyone who knows more care to chime in to confirm or deny? Neuro?

I suspected somebody would ask about that...I just didn't expect it so quickly.

It'll take me a bit to put together some example images..."please hold...."

b&
Title: Re: Please explain the need for f2.8 zooms
Post by: Drizzt321 on February 01, 2013, 09:17:49 PM
Huh? I have never heard that the in camera meters underexpose, and then do a digital push. I know that different camera makers have different amount of eV's per 'bin' of bits in each channel. Anyone who knows more care to chime in to confirm or deny? Neuro?

I suspected somebody would ask about that...I just didn't expect it so quickly.

It'll take me a bit to put together some example images..."please hold...."

b&

Not looking for example images, I'm looking for the more technical reasoning and explicit knowledge of the HOW the metering systems work, not images you've taken.
Title: Re: Please explain the need for f2.8 zooms
Post by: TrumpetPower! on February 01, 2013, 09:53:33 PM
Not looking for example images, I'm looking for the more technical reasoning and explicit knowledge of the HOW the metering systems work, not images you've taken.

The images help with the explanation.

I'm attaching three of them.

The first is a linear UNIWB development of a half-a-second exposure of a ColorChecker Passport. That is, this is what the sensor actually recorded dumped to a TIFF and scaled down for the Web. Because of the 1.0 gamma (you're used to seeing 2.2 gamma), it's very contrasty. And, of course, it's rather green, thanks to there being as many green pixels on the sensor as red and blue combined. But, aside from those two caveats, you can see that it's properly exposed. You can also guess that the sky is quite blown.

The second is the same file but white balanced and with a 2.2 gamma. But no digital gain or tone curve is applied. You can see that the colors are a bit muted, which is because there's no ICC profile associated with the image and the camera has a wider gamut than your monitor. But the exposure is clearly correct.

Last is the 1/8 second exposure similarly developed. That's what the meter read, if I recall right. It's clearly underexposed, but the sky's no longer blown.

In other words, the half-second exposure caused the sensor to record the scene such that an 18% gray object was rendered as 18% gray (that'd be 45.9 on a 0 - 255 scale, again remembering the 1.0 gamma; with 2.2 gamma, that works out to the much more familiar 118) in the digital file. The 1/8 second exposure caused that same object to be rendered instead as 4.5% gray, or 11.5 on a 0 - 255 scale with 1.0 gamma. In other words, it's two stops underexposed.

And now you should also have an idea of why shadow noise has always been such a problem for digital cameras....

Cheers,

b&
Title: Re: Please explain the need for f2.8 zooms
Post by: sdsr on February 01, 2013, 11:41:44 PM

The thing to know about the 6D, is it's not really considered a 'professional' camera as such. Sure, it's a fine camera, but features and build quality is generally not up to 'pro'. Heck, Canon only calls the 1D-series as 'pro' cameras, everything else isn't.

When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance? Even though the center point AF sensor works fine with f/4 lenses, I believe it also has a double cross-point sensors there which are likely only available on an f/2.8 lens. Thus, you still get the point where your AF will likely be improved by having an f/2.8 lens, even if you take the shot at f/4 or f/5.6, even in available light.


That may be true, but I will note - for whatever it's worth - that my 70-300L, at 300mm (where it's quite far from 2.8!), focuses flawlessly on my 6D (center point AF) in *very* low light (including in a situation where a Nikon D600 I was trying simply wouldn't focus at all even with a f/1.8 lens attached).  Whether less well-designed/made slow(ish) lenses could do as well I can't say....
Title: Re: Please explain the need for f2.8 zooms
Post by: bdunbar79 on February 02, 2013, 01:43:49 AM

The thing to know about the 6D, is it's not really considered a 'professional' camera as such. Sure, it's a fine camera, but features and build quality is generally not up to 'pro'. Heck, Canon only calls the 1D-series as 'pro' cameras, everything else isn't.

When you say 1 stop better, are you just talking about sensor noise performance or AF sensor performance? Even though the center point AF sensor works fine with f/4 lenses, I believe it also has a double cross-point sensors there which are likely only available on an f/2.8 lens. Thus, you still get the point where your AF will likely be improved by having an f/2.8 lens, even if you take the shot at f/4 or f/5.6, even in available light.


That may be true, but I will note - for whatever it's worth - that my 70-300L, at 300mm (where it's quite far from 2.8!), focuses flawlessly on my 6D (center point AF) in *very* low light (including in a situation where a Nikon D600 I was trying simply wouldn't focus at all even with a f/1.8 lens attached).  Whether less well-designed/made slow(ish) lenses could do as well I can't say....

True.  I won't argue the focus speed on f/4 lenses is just as good in most situations.  But for low light action, with an f/4 lens, you're in a world of trouble with ISO values.  A whole stop of light could mean ISO 10,000 or ISO 5000, which is a huge, huge difference in IQ.  If you can slow your shutter, great, it'll work fine.  But not at 1/500.
Title: Re: Please explain the need for f2.8 zooms
Post by: RLPhoto on February 02, 2013, 04:19:26 AM
When I post a comment that's been simplified, it tends to bend some users out of shape but there is always experience behind it. I also know the math behind a particular subject in photography but I don't key on it, it's boring as heck.
Title: Re: Please explain the need for f2.8 zooms
Post by: wickidwombat on February 03, 2013, 03:52:14 AM
x-sync is irrelevent when dragging the shutter since you are shooting at 1/10th second or so

Wow, I really have to try that - but 1/10s does result in shots with a large motion trail that are rather "artistic", doesn't it? Or you could even pull a sample shot out of your stack :-) ?

I thought more of a 1/60s as the lower limit (and conveniently settable in the camera fw), and the upper x-sync limit with 2nd curtain was meant if for fast motion 1/500s+ would be more appropriate, but a lower shutter speed captures more ambient/background light at acceptable iso.

Sorry for the delay to answer your request been quite busy
here is one from a pre wedding shoot on thursday
the trick is to make sure your subject would normally be a silhouette when not flashed
that way the pixel wells are empty when the flash fires at the back of the exposure to fill them up
i've attached 100% screen shot and LR shot with no flash firing
these were 1/20th
Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on February 03, 2013, 03:57:15 AM
Sorry for the delay to answer your request been quite busy

Which probably makes your advice a good one :-)

the trick is to make sure your subject would normally be a silhouette when not flashed
that way the pixel wells are empty when the flash fires at the back of the exposure to fill them up

Great advice, thanks again - as most things, it seems obvious if you know the technique, but I didn't think of it or read it anywhere else. I'll certainly use that when I want to integrate a low light background.

EDIT: Um, another probably dumb question: Why did you shoot that @iso100 - for demonstration purposes, because of the added dynamic range, because of highest possible iq or because you are on full manual? Afaik iso400 whouldn't have made such a difference, but the background would have been captured with a faster shutter time?
Title: Re: Please explain the need for f2.8 zooms
Post by: wickidwombat on February 03, 2013, 06:12:35 PM
EDIT: Um, another probably dumb question: Why did you shoot that @iso100 - for demonstration purposes, because of the added dynamic range, because of highest possible iq or because you are on full manual? Afaik iso400 whouldn't have made such a difference, but the background would have been captured with a faster shutter time?
For dynamic range, and highest possible IQ
as it was at iso 100 the sky can blow out really easily
I could have used Iso 400 and a faster shutter

another thing not noticable on this shot but if shooting on a beach with bigger waves the slow shutter speed gives really nice motion blur of the waves in the background too

2nd curtain sync is a very under used function IMO

also funnily enough back on topic, when going through the images of this shoot I didnt take a single shot wide open. I was using the 85 f1.4 on the 5Dmk3 and the 16-35 on the 5Dmk2 (my favourite combo) most shots i was at between f5.6 to f8

Title: Re: Please explain the need for f2.8 zooms
Post by: Marsu42 on February 03, 2013, 07:20:20 PM
For dynamic range, and highest possible IQ
as it was at iso 100 the sky can blow out really easily
I could have used Iso 400 and a faster shutter

Indeed, I recently noticed that dr @iso100 is not much different from iso400, or iso800 for that matter. Not because Canon has great high iso dr, but low iso dr is so crappy vs. Nikon: http://www.sensorgen.info/ (http://www.sensorgen.info/)

also funnily enough back on topic, when going through the images of this shoot I didnt take a single shot wide open. I was using the 85 f1.4 on the 5Dmk3 and the 16-35 on the 5Dmk2 (my favourite combo) most shots i was at between f5.6 to f8

Exactly, I noticed that, too (and it's in line with the book I mentioned in the op) - but I didn't write it because I'd fear to be flamed to a crisp :-p