L-series professional f/1.4 wide-angle lens with an aspherical lens element to correct aberrations. The floating system enables high picture quality to be obtained over the entire focusing range. Autofocusing is quick and quiet with rear focusing and ring USM. Full-time manual focus is also available.
sharpness, optical quality, fast f/1.4,
well none, but price ($1300) :)
beautifull lens - saturated, sharp and CA free
normal wide with cropfactor, naturaly wide with fullframe
rarely put this down from my 20D