It is the best full-frame fisheye that I know for Canon EOS cameras! I already had the predecessor of FD EF 2,8 / 15mm. The lens goes to the limit of what is possible. I'm using it currently mostly for creating 360 ° panoramas (including ball-Panorama). It brings an excellent performance with my EOS 5D. What is even more positive note, it has a holder for film / Gelatinfilter at the back.