Recently, I was going through old cases of some of my early photo equipment. My F-1 with the original brick-sized motor drive. (Whoa, hold me back! 3fps!) I lovingly looked at my EOS3 with eye focus that actually worked (and which at times liked more than my EOS1). And then I saw it. My cherished 500mm f8 mirror (reflex) lens. Ah, many fond memories -- including how critial focus could be. How I wished Canon had created an autofocus version. Sony did it recently. Why not Canon? Then I started my search for a decent FD to EF adapter. I actually found tow, both of which I ordered. One via Amazon, made by (or marketed by) Fotodiox. The other from some non-descript company in China. The difference: Fotodiox uses a "corrective element", which makes it more like a 1.2x converter, the Chinese one (which is enroute), uses nothing. I have the feeling the lack of a corrective element might not make a difference since since mirror lens in general seem to focus beyond infinity.
I was pleased with the Fotodiox results, generally speaking. It vignettes incredibly on the edges (might not be an issue with an APS-C camera), but is remarkably sharp in the center (if I can get it in focus!). The presence of the corrective element also does introduce some chromatic aberration, which is usually not something greatly present in a reflex lens. One beauty of digital is that you can ratchet up the ISO with some degree of impunity, versus the old days of only reluctantly switching to 400ASA film. I've only shot some informal shots with it -- my kids' soccer games -- doing both stills and video with my 1Dx. The video is actually pretty good and sharp, considering I'm a little rusty doing manual follow focus. Ditto for stills. Here are a few samples for the curious. I'm looking forward to receiving my "non-corrective lens" mount adapter this week and will keep you posted.