Absurd Singularity

Ok, I don't have as much time as I used to in my prior pixel-peeping posts so I'm going to make this quick. I'm posting a couple of 100% center crops at f/2.8 and at 24mm, 35mm, and 70mm for the Canon 24-70mm f/2.8L, Nikon 24-70mm f/2.8G AF-S and Sigma 24-70mm f/2.8 EX DG HSM lenses and my thoughts on them. All shots were taken on a tripod, no flash, ISO 200, RAW, opened in Photoshop CS4 with NO sharpening whatsoever and color/exposure adjusted to match across the board. Saved to JPEG w/quality set to 10. Each individual image below contain 4 slices: 1 each for Canon and Nikon and 2 for Sigma (1 w/autofocus (AF) and the other with manual focus (MF)). Focus was on the white book with purple lettering and light grey lines. The white book to the right of this one is at the same depth. The two books to the right of that is about 5/8" in front while the two books to the left are 5/8" behind. Before I took the crops, I had to shrink all the shots taken with the Canon 5DII down to the same dimensions as the D700 (5616 to 4256 width). Make sure to click on each image to see full size.

So, at 24mm, besides some color differences with the purple lettering, everything looks acceptable across the board. Although it appears that the Nikon and Sigma AF are front-focusing just a bit.

At 35mm, the Canon and Sigma (MF) look quite comparable. Nikon looks pretty good too but shows a little bit of front-focus as the red book all the way to the right seems to be more in focus than in the Canon and Sigma (MF) samples. The Sigma (AF) crop looks fuzzier than the others but the red book on the right looks well in focus.

And finally at 70mm, everything looks comparable except for Sigma (AF) which is way fuzzed out. This is the front focus issue I mentioned in my earlier post.

So, what's my conclusion? Well, when it comes down to center sharpness, all 3 lenses are quite comparable in my opinion. Sigma's downfall is its unusually bad autofocus. When the focus is on, it's darn sharp. If I really want to keep it, a trip for the 5DII body and lens to Sigma would definitely be necessary.

This copy of the Canon that I currently have is the sharpest I've seen wide open at the long end and I've been through quite a few. Downsizing the Canon 70mm sample caused it to lose a bit of detail since at native size, it's quite apparent that the light grey lines on the focused-on book are zig-zag which I've only seen resolved by 3 other lenses wide open that I've tested: the Canon 17-55mm f/2.8 IS at 55mm, Canon 70-200mm f/4 IS at 200mm, and the Pentax 17-50mm f/2.8 at 50mm. Actually with the full sized, manually focused shot of the Sigma, you can make out the zig zags a little bit as well.

As for the Nikon lens, it's no slouch either. This particular copy may be front-focusing a little bit on my D700 body but it's definitely not as bad as with the Sigma and is probably something I can fix with the micro-adjustment feature if it really bothers me (which it doesn't at this point).

Anyway, if you want to check out the non-cropped, full-sized shots (JPEG) for each lens so that you can check out the edges and corners and color and whatnot, you can download them all here. I didn't bother putting up stopped down samples cause there wasn't anything out of the ordinary with them and nothing new that you can't tell from the wide open samples. A bit sharper than at f/2.8 and not much difference between the brands.

So, is the Sigma worth it? At $900 it's about $350 cheaper than the Canon version and $800 less than the Nikon. If you want to take a chance that you'll get one with perfect autofocus, then yeah, the combination of size, IQ and price is pretty great. Especially if you're in the Nikon camp. Even if you're a Canon user, $350 is nothing to scoff at. But definitely test that focus at 70mm immediately if you do get one. Hopefully you'll have better luck than me.