April 17, 2014, 01:43:05 AM

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Messages - Albi86

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376
Did Sigma resurrect steve jobs or something? They're like a whole new company now, good for them. Although I was gutted when I found out the 18-35 1.8 was for crop, would have been awesome for ff.

The son took over the family business  ;)

377

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.

378
Have to respectfully disagree. An inferior lens manufacturer would make lenses other than what Canon offers so as to offer no apples to apples comparisons. Sigma is making (so far in their art line) superior lenses in critical flavors that go head to head with the best that Canon has...

There's only one superior lens in their art range at the moment, the 35mm f1.4. But like many Sigma lenses before, how well does it focus? The rest of Sigma's range are sub par with Canon counter parts. With Sigma, you get what you pay for.

You are terribly misinformed. The new 35mm focuses like a dream. And the USB dock has been designed to counter possible tricks by Canon in the future.

And the statement in red is plainly false.

379
How (or where) do the new ART lens series compare to their EX series?

I like the Sigma lens I own, but the naming nomenclature is getting more and more confusing.

The EX designation has been set aside.

Now all lenses are (supposedly) in the same quality league. They divide them based on the intended use: the ART segment includes fast lenses for creative use, CONTEMPORARY includes popular zooms, while SPORT includes fast teles for action/wildlife.

I have both the 135 F2 and 200 F2 and with the 200 and IS you can easily shoot 1/30 or 1/50 all night long and if Sigma can do this, it would be like a mini 200mm F2 (and probably a lot lighter).

Actually, it'd be a mini 200mm f/2.8.

135 / 1.8 = 75
200 / 2.8 = 71
200 / 2.0 = 100

A mini 200mm f/2 would be a 135 f/1.4. And that would not at all be small, lightweight, cheap, or discreet. Imagine the bastard love child of an 85 L and a 200 f/2.

But this rumored lens, if it becomes real, would still quite impressive nonetheless.

b&

What I meant by 'mini' is the 200mm f2 smaller brother. Going to weddings and shooting a 135mm at 1/50 SS could save you a couple stops of noise. From your example, the 85 / 1.2 = 70 could be the smaller brother to the 200mm f2.8 ?

Sorry, how are this calculations done? To me, I agree, it's a little brother to a 200 f/2 - if it's sharp enough for the cropping.

380
"well , then you need to WB against a qp-card etc to know what you are doing and to  se what you get, it tells nothing that you select a Kelvin number."

Ah No, I don't need to White Balance against a card to "know what I am doing".
I know exactly what I'm doing - I'm selecting identical Kelvin numbers for White Balance for each camera.

"It tells nothing"

Again No, it definitely tells me something. It tells me that Nikon's Auto White Balance or White Balancing by Kelvin number is terrible under the lighting I had set up. Canon is much more accurate.

"Was it RAW or JPG?"
If you had read my post you would realize I was filming (VIDEO!) no RAW or JPG.

Ankorwatt's point probably was: you can see that they are different, but without a reference how do you know which one is correct?


381
Yes, all nice. But i am not worried about the need of such a lens. More about the possibility to even build it! (For a price someone can pay)

A 135mm f/1.8 lens has the same size physical aperture as a 200mm f/2.8 lens. I'm pretty sure this lens would be cheaper than Sigma's $1,300 70-200mm f/2.8 OS, seeing how it's a much simpler design. I'd also guess that it'd be cheaper than Canon's $1,000 135mm f/2 L, because that tends to be how Sigma rolls. I'd personally guess somewhere in the $800 range.

Cheers,

b&

Sigma's 180mm f/2.8 OS Macro is faster than Canon's equivalent, and has OS, and is more expensive. It might be a precedent for this lens's pricing. My guess is about $1,300.

I also wouldn't be surprised. It would be faster than the Canikon equivalent, and with OS. I guess something around 1100$ at launch.

For me, as a FF + crop shooter, this lens could replace the purchase of a 300mm f/4 - if it takes TC well. Overall a lot of value if one lens is both a fast portrait prime and a sharp stabilized tele.


382
I'd rather see Sigma do a 19mm or 20mm or 21mm wide angle "A" lens. There's nothing available for Canon that's a prime, wide and auto-focus.

Canon's widest is 24mm and if Sigma did a 24mm, they'd just be copying Canon. They should man up and do something new.

That could be said about the 35mm too, but it seems that it made many people happy (including me).

24, 28, 35, 50, 58, 85, 100 and 135 are very popular and "recognizable" focal lengths. Canon, Nikon, Sony, zeiss etc have their own version. Sigma is just joining the big game - at least for now. However they had a 20mm, so it might be that something wider will come.

I wouldn't buy the 50mm. The focal length on ff is too similar for me - just a bit of cropping. However, the run lured 135mm.... That's another story.... Slurp!

383
My oh my. If it takes 2x TC well you end up with a stabilized 270mm f/3.5.....


384
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.

385
EOS Bodies / Re: 21mp Sensor in the 7D Mark II? [CR1]
« on: April 19, 2013, 12:27:59 PM »
And why didn't they bring the 70D already, since it is overdue after 2 1/2 years, when Canon has all the stuff they need (including sensor) ready. It looks to me (and I hope so), that they are delaying the 70D so they can introduce it with the new sensor.

Who said it was overdue and/or that they're delaying the 70D?  Internet expectations?  Or Canon?  Perhaps Canon believes they're ahead of schedule.  Because other than some not-so-vague comments from Canon employees who were put on the spot, I don't recall reading/hearing anything about the 70D or the 7D2 especially in regards to an impending announcement or due date.

So again, are these YOUR expectations from reading a RUMORS site, or are these missed deadlines that Canon has self-imposed?  Obviously a rhetorical question...

Talk on this website has REALLY gone from "rumors" to "if _____ doesn't fit my personal expectations then it's ______ (fill in the blank with negative thoughts)."

Have you ever heard about competition?

Canon is deciding on the sensor while the D7100 has been shipping and making people happy for a while. That's what makes Canon look late. They're not the only player in the game, and the show goes on with or without them.

386

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.

388
...

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.

389
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.

390
...

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.


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