SIGMA 24-70 VS. SIGMA 17-70

Janika wrote in post #2548347
The constant 2.8 aperture is more of a mith than a so called "big" plus. The very reason why I got rid of my 18-50 2.8 EX

What do you mean?

I would agree with this in terms of build-feel. When I handled/had both the 1770 and 1850, I thought to myself the same thing: they really do feel similarly robust, but the 1770 doesn't have the EX label on it. Optically it is impressive too.

I tend to shoot wide open a lot with all my glass, including when I had the 1850EX (and 1755IS), so I think this is really shooter-dependent.

Photolistic; I was very excited about the constant f/2.8 and after a few weeks of use, I realized that I am at around f/4 to f/11 most of the time, so what's the point?! Plus it had some CA and BD wide open, more so than my new 17-70. I ended up parting from the 18-50 EX...

AdamJL wrote in post #2546195
What exactly is a full frame lens?

Assuming that you're a newbie.
Its the lens that can be used on cameras like 5D

farrukh wrote in post #2548416
Assuming that you're a newbie.
Its the lens that can be used on cameras like 5D

Not a newbie at all... but I wouldn't call that a full frame lens.
I'd call that a lens
And I'd call the 17-70 a crop lens, because it can't be used on full frame.

Photolistic wrote in post #2548373
What do you mean?

x2.

Layston wrote in post #2546557
My copy of the 24-70 I find fast to focus, not overly loud (doesn't bother me, but I've never owned a USM lens so...) and rarely hunts. I shoot indoors a lot, but I also typically have the ability to turn on lights if I want. I can't say what this would be like in a dark club etc.

But to answer your question AdamJL. A "Full Frame Lens" is one designed such that it's image circle is large enough to cover a standard 35mm film frame or a "Full Frame" sensor which is roughly the same size as standard 35mm film. The 300D, 350D, 400D, 10D, 20D and I think 30D all are "crop" cameras with APS-C sized sensors which are smaller than 35mm film. Lens manufacturers are making lenses that fit these cameras but if you put the lens on are "Full Frame" camera, you would not cover the entire sensor and the corners would be dark if not black. Canon's own EF-S lens line does this, but they have the added problem of only fitting a few cameras, the 10D does not work with EF-S lenses even though it has the smaller sesnor because the EF-S lenses have a special mount that the rear lens protrudes further into the camera and the mirror would hit it as it moves.

Do some searching and there are better more technical details of "Digital Only" lenses and EF-S lenses here. But that's why the 17-70 is "Digital Only", it does not cover a full 35mm size sensor or film, it is designed specifically to cover APS-C sized sensors.

Yeah I understand that... I just don't agree with the term "full frame lens".
A lens is a lens, and will work with anything unless specifically designed not to. And in that case, the lens is different and can be noted differently, like Canon's EF-S lineup.

I'm probably being pedantic, but it's the little things that make a difference. It's like people who say crop cameras change the focal length of the lens, when in fact, they do not.

AdamJL, not to break this out into an argument, but I think people are making the point that the 24-70 is full frame compatible whereas the 17-70 is not. Yes they could say that the 17-70 is "one of Sigmas DC lenses designed specifically for Digital cameras with crop factor" but it's much easier to say that the 24-70 is FF compatible.

And as far as focal length change, using a crop factor changes the EFFECTIVE focal length of the lens IN COMPARISON to a standard 35mm camera. Remember for users like myself who have used film cameras for decades, being able to talk in RELATIVE terms to the knowledge we already have is very important. Otherwise the frame of reference is lost and you end up talking two different languages with the same words and everyone is confused. And yes, I can see that you know this and I agree the term "full frame lens" is misleading, but "FF compatible" I think is totally acceptable and even correct terminology.

Layston wrote in post #2549142
AdamJL, not to break this out into an argument, but I think people are making the point that the 24-70 is full frame compatible whereas the 17-70 is not. Yes they could say that the 17-70 is "one of Sigmas DC lenses designed specifically for Digital cameras with crop factor" but it's much easier to say that the 24-70 is FF compatible.

And as far as focal length change, using a crop factor changes the EFFECTIVE focal length of the lens IN COMPARISON to a standard 35mm camera. Remember for users like myself who have used film cameras for decades, being able to talk in RELATIVE terms to the knowledge we already have is very important. Otherwise the frame of reference is lost and you end up talking two different languages with the same words and everyone is confused. And yes, I can see that you know this and I agree the term "full frame lens" is misleading, but "FF compatible" I think is totally acceptable and even correct terminology.

"FF compatible" I agree with wholeheartedly; "FF lens" I don't because it implies that it can only be used with a FF sensor.
And as my last hijack, I have to say I don't agree with the term "effective focal length" (whether compared to a crop-sensor or not).
A change in Field of fiew would be the better term to use to describe the change caused by a cropped sensor. This is because a crop sensor also changes the depth of field. A fast lens has a smaller depth of field on a FF sensor.
The focal length always stays the same. 20mm is 20mm on a 1.3, 1.5, 1.6 or FF sensor.
But anyway, no arguments, just healthy discussion
I won't hijack this thread anymore, so if you would like to continue let me know and we can discus via PM

Yeah I dont care if its full frame or not. As long as it works on my camera.