It’s also quite sharp, especially in the center and especially at 8 to 10mm, which is probably what you’re getting this lens for anyway. More surprisingly it doesn’t have horrible barrel distortion at 8mm, which is pretty amazing. At the longer end it’s not quite as sharp, and at any focal length the corners and even the edges are a little mushy. Chromatic aberration is pretty well controlled too.

So I’m surprised: I expected to say it was a useful lens if you really want the widest you can get but otherwise had a lot of weaknesses, which is what I said years ago about the 12-24 full frame lens. But really this one not only lets you get ultra, ultra wide, it can compete with all the other ultra wides from 10 to 20mm too. It gives up some aperture to most of the others, but except for that its very comparable to them. And from 8mm to 10mm, well there’s no comparison at all. This isn’t the lens for everyone, many people will never shoot this wide, but if you think you might, this is a great choice and I can recommend it without reservation.

Comparisons

Comparing the ultra-wide, crop sensor camera lenses is an extremely difficult task, so I’ll put the summary first: they all deliver excellent image quality and you can’t go wrong with any of them. To my ‘just taking pictures’ assessment they are all excellent. There are some differences though, so I’ll try to point those out so you have a better chance at choosing the one that’s best for you.

The Sigma 8-16 f/4.5-5.6 is the widest (and remember, 8mm is 20% wider than 10mm, so it’s a very real difference). Not quite as sharp in the corners as the others, and lower maximum aperture, but it’s really pretty good, especially considering it’s the widest of the wide.

The Canon 10-22 f/3.5-4.5 is arguably the most flare resistant, the smallest and lightest when that’s important, and has low distortion. It’s also the most expensive and vignettes a bit. I like it a lot, though, and often find myself preferring it because of its small size.

The Sigma 10-20 f/3.5 has a bit more distortion than the others but delivers very nice images and is also built much better than the Canon 10-22. It does everything well.

The Tokina 11-16 f/2.8 gives you the widest aperture if you’ll be working in low light (with ultra wides, depth of field is rarely an important point), but it’s a bit soft at f/2.8, so the aperture advantage isn’t huge (I usually shoot it at f/3.5 if I can to get it sharper). It has very little vignetting and distortion, probably the least of the group. Unfortunately, it does show quite a bit of chromatic aberration at times. Overall it may be the best image quality of the group.

The Tokina 12-24 f/4 PRO DX II is built like a sturdy tank (and therefore a bit heavier). It does tend to give low contrast images when shot into the sun but is quite sharp otherwise. This is the one I’d take if conditions were rough: I pity the rock this bad boy falls on. Poor rock.

But like I said above: they’re all excellent. We hardly ever get anything but happy comments about any of them.