Are there any downsides of converting an old FD(n) lens to the EF by means of actually replacing the mount with a EdMika or similar? The lens will become a manual focus and manual aperture control lens, but will be a very affordable one since old lenses are quite cheap.
I've tried to think of possible shortcomings of the result, but I've only come to think of
- Only manual focus and aperture control
- The viewfinders brightness will suffer when using high apertures
- There will probably be more lens flare in older lenses, given the lack of multi-coating
- When focusing at certain distances the back element may protrude so far back into the camera body that it could be hit by the mirror and possibly damage it or get damaged itself
As long as using it for portrait at large apertures that would require manual focus anyway or video recording it seems like an affordable option to consider at least. Is there anything important I've missed that would render it pointless to convert old lenses.