Summary: Very nice lens, AF motor is not the quiet type, but it works great on my full-frame Canon and it is NOT a fish-eye in case that's isn't evident. Good luck finding a replacement lens cap for this one, it's a cheap piece of plastic that some swindlers are selling for $60.
Summary: Nice lens for the price.. Been looking to get a 17mm-50mm lens for my 5d mark ii.. These seem to be really good for landscape photography... They are some nice lens to have in your procession only if you are going to use them greatly..
Summary: I was in the market for a wide angle zoom for full-frame Canon cameras (5DMkII). I purchased an older Canon 17-35 f2.8 L lens as my first choice, but I was not very happy with results. I own this lens in the Sigma SA mount, and loved it, so I found this one.
Conclusion: I am really quite impressed with this lens on my 5d. It is sharper than I expected with no decentering at all. Sharp to the edges with the exception of the extreme corners, but overall an excellent performer fo an UWA. It is large, but not too heavy. I find the focus plenty fast and accurate enough.
Pros: Sharp, accurate focus, nice color, well built.
Cons: Some vigeneting on full frame, but easily corrected. Need to watch for flare.
Summary: Even though this lens covers a full-frame, its zoom range is wide enough that it is useful even on a crop camera (60D) on which its EFL is 24-48 mm. With the type of shooting I do, I need a wide angle of 24mm or more, so I'm often using this lens at its widest setting of 15mm.
Conclusion: if you don't need wider than 15mm than this lens is a bargain. I used this lens for youears without any problems, only the AF was loud. Lens is much sharper than the Sigma 10-20DC lens, very good from f7.1 and the corners are sharp from f9-f11.