Has anyone ever done this with much success? I believe I've found a new method that makes it MUCH easier to accomplish. With a standard lens for a 35mm or APS-C based camera, you'll find that there's virtually no distance to play with. Knowing that the flange distance on a medium format camera is much longer than that of a standard DSLR, I thought it would be fun to try a Mamiya 645AF lens on a Canon 5D3. Much to my surprise, it works, and it works very well. I'll post up a result once the bossman gets off his ass and sends it to me (forgot to snag the card). I would highly recommend trying this-it's fun and free if you have some MF lenses laying around (or cheap if you don't-M645 manual lenses are dirt cheap).