Thanks Rick. The Zeiss 21mm with the Canon EOS 5D Mk.I is a killer combination. It produces sharper images straight out of the camera. It may be that the 12.8 Megapixel sensor has a less severe Anti-aliasing filter in front of it VS the Mk.II. Certainly an easier camera to use. I wish the Manufactures would drop the Anti-aliasing filter altogether. Steve