Fisheye lenses don't have the rectilinear correction in them. If you walk up towards a wall, your brain automatically processes that it's flat. However, a lens needs to make certain corrections so that a picture of a flat object appears flat (if perpendicular).


Many people love the EF-S 17-55. I don't like the fragility of its IS unit though. You could also consider the 17-40/4, the 16-35/2.8II, the EF-S 18-55 or 17-85 or 15-85, or the excellent EF-S 10-22.