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 – that way you can better choose what’s best for you.

• 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). It’s not quite as sharp in the corners as the others and has a lower maximum aperture, but it’s really pretty good, especially considering it’s the widest of the wide.

• Nikon 10-24 f/3.5-4.5G shows a fair amount of barrel distortion at 10mm (note to self: never take girlfriend’s portrait with this lens) and doesn’t have the best corner sharpness of the group. It’s got the largest range and is fast to autofocus, which makes it a great wide-angle walk-around lens. If I were mostly going to shoot at 15-24mm and occasionally shoot wider, this would be a great choice. If I were going to take lots of 10mm scenic shots, I’d probably look at one of the others—- they’re a bit better at 10mm.

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

• Nikon 12-24 f/4G has exceptional center resolution and is very flare resistant but does show some field curvature at 12mm @ f/4. The border quality is also impressive though a little less field curvature may be desirable at 12mm. It’s a very good lens, maybe better than the competition, but not as much as its price would suggest.

• Tokina 11-16 f/2.8 (version I or II, they aren’t very different) 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.

• Tokina 12-24 f/4 PRO is built like a sturdy tank (and therefore a bit heavier). It’s a good lens but does tend to give low-contrast images when shot into the sun and has a tendency to show some chromatic aberration when objects are backlit. This 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.