I have used OM lenses on my 1Ds, as well as old Pentax super-takumar 50mm 1.4 on my camera, and they all worked fine. Of course it only is manual focus, but it does't bother me. I want to KEEP my lens, as it is truly stellar. I am eying an F5, but also on the list is an EOS-3 and F4. I would love a 1V (as the layout is the same as my camera now), but they are still going for $500+..