My good buddy Keith lent me his Tokina 11-16mm f2.8 AT-X PRO super wide-angle lens this week to play with. Despite it being a third-party lens, it is a very high quality lens comparable to other top notch UWAs, such as the Canon 10-22mm. The distortion at 11mm is very slight, while at 16mm, distortion is almost non-existent. Sharpness when stopped down 1 stop from f2.8 is very good, and at f8.0, it is incredibly sharp across the frame. The build quality is solid, the zoom ring is smooth, and the lens is quite compact.
But then I started to wonder, just how much better is the Tokina as compared to a standard zoom lens, at wide angle 28mm? So I decided to do a quick, unscientific test between the 11-16 and my Canon 17-85 f4-5.6 IS USM. I'm just investigating the optical quality here, and my test does not take into consideration other factors like price, build quality, weight etc.
So I got my 500D steadied on a tripod and shot 2 frames at 15MP, deliberately ensuring there were high contrast areas in the picture so I could compare chromatic aberration.
I shall let the pictures speak for themselves, and yes you may pixel-peep. Click to enlarge.
11-16 (Resized, with slight crop):
And now for the 100% crops where the difference is noticable:
The conclusion is simple and clear-cut: if you're shooting at 28mm most of the time, get the Tokina 11-16 over the 17-85. The Canon's chromatic aberration is horribly bad compared to the Tokina. Sharpness wise the difference is less obvious, though the Tokina is much sharper of course.