Originally Posted by CharlesDAMorgan
A good question, but I tried that with a Voigtlander VSL (1 or 2 - I'm away from home at present) and while the lenses should fit, the early Zeiss made and branded QBM lenses actually don't mount at all well to the camera - the mounts are subtly different enough. The later Rollei ones do - so as a body it would not work with the Sonnar and the Distagon I have. Which is a shame.
The irony of course is that the Canon's autofocus is incredibly fast - with the kit 35-70 it came with - so much so it beats the pants off the Nikon F90X and F80 I have and is considerably more accurate. I don't use AF much, but when I do I want what the Canon offers. So I shall be mounting manual lenses on it...
If you like the 650 autofocus you'd love the 600/630 then. Owning 650, 620, 630 & RT models concurrently for some years the 630 is faster as, indeed Canon claimed when it was released. I expect the 1 series were faster again but you have a preference for lighter bodies, so...