Canon EF 300mm f/2.8 L USM Reviews

There are very few lenses that can take full advantage of the 17Mp Canon EOS-1DS-MkII. This is one of them. It's sharpness and contrast are the best of any lens I've ever used, including the Nikon version of it. Primarily used for nature photography where sharpness is critical, the USM autofocus works very well--one can typically get the pupil and iris of a Heron in flight to be razor sharp with the bird at about 1/3 frame. It is interesting to note that with the 1.4x Canon teleconverter and the 17Mp sensor, the lens/converter combo is noticeably softer, such that in still air, the enlarged image wihout the converter has about as much info as the larger image with the converter. Built like a fighter plane.