Comments about Sigma Sigma 28mm f/1.8 EX DG Aspherical Macro AutoFocus Wide Angle Lens with Hood for Canon EOS Cameras - Gray Market:

Bought this lens new and right out of the box it does not autofocus correctly at all. Not just a little bit off, but quite ways off. I think it is front focusing by more than an inch and a half! It's worse when your subject is farther away. I am still trying to figure out how bad it is. On my Canon t2i the only way I can get good focus from this lens is to manually focus using the live view mode. Even manually focusing through the view finder is not accurate.[...]Other Canon and Tamron lenses on my Canon T2i is autofocusing spot on so it's not a camera issue. If you'regetting this lens please make sure you're getting a good copy.