i have a Hasselblad 30mm lens I would call a fisheye and an adapter to use it on my Canon 7D. I tried it and yes its cumbersome and must be used in manual or aperture prioity mode but am having trouble as the aperture reads 00 and there appears to be no method to adjust it. Everything I have read so far suggests setting the aperture to 1.0 .......I guess thats if you can figure out how. I can adjust the aperture and focus on the lense, no trouble there, but not the camera. Anyone have a suggestion, please....and not the suggestion of "why"? or go get a dedicated Canon Lense...Please. Im aware of that and that I may be beating a dead horse. Thanks to any positive suggestions.