Canon FD to EF mount change

This model should allow you to convert your old Canon FD lenses to the more modern EF mount. This model has been specifically created for Canon FD 135mm f/2.5, and may need further adjustments if you wish to convert a different kind of lens.

I have designed it by iterating over measurements, and then fixing the problems along the way. Commercially available conversion kits do exist, unfortunately they cost more than the lens itself, no files are able to be bought.

The mount conversion should allow infinity focus of the lens, which normal adapters do not (the lens cannot “move invard enough”), after you swap the mount, you also need to readjust this distance. This is done by unscrewing the top part of the lens (3 screws) and then moving a plate that stops you from focusing the lens. I also needed to move the rear element and suspend it above its screw-in part, but this may vary from individual lens to lens, you need to experiment.

I have been able to get these results while focusing on a star with a bahtinov mask:

And a stacked, lightly edited photo taken with this lens:

I printed this in PLA and PETG (which might be more suitable for longer use), the arm is printable without supports, the adapter / mount is not. I reccomend hybrid tree supports, it is easier to remove them afterwards.

For (dis)assembly of the lens I would highly recommend this video:

You can also find all of the code on GitHub: https://github.com/Biosias/canon_fd_to_ef_adapter