I bought a sigma 10-20 a few weeks ago. None of the pictures I took with it at first seemed sharp. f8 af. The only time it seemed sharp is when the subject was right in front of the lens. I finally started looking at the distance scale, and I noticed that it never goes to infinity in af. It stops at 3'. When I put it in mf and turn it to infinity the pics seem sharper. When the camera hunts for focus it will go to infinity, but it comes back to 3', so the focus motor works.... Is my camera too stupid to focus it? Or does the lens have too much distortion and the af sensors don't know what to do with the image? Ps it focuses all of my other lenses just fine.