FD-EOS Converter - Mods to FD Lenses

[CoolToolGuy]

I have the Canon FD-EOS converter and I got a used FD 400 f4.5 SSC lens from KEH to use with it. The compatibility chart shows this lens as compatible, but it also has a note that certain of these lenses will not be compatible. I think I found out why.

The copy that I got is a bayonet FD mount, and in the rear of the lens, near the mount, is a rectangular mask like an internal hood. The FD-EOS converter is much like a Canon EOS teleconverter, with an element that extends into the back of the lens. The mask prevents the converter from being mounted. The later versions of this lens have a mask that accommodates the converter.

I have looked at the mask and it appears that I could 'hog out' the metal to clear the converter. It seems to have no mechanical functions, and since the converter extends further into the lens it would not serve any optical purpose. I could probably remove it altogether, although I have not taken it apart as of yet.

Has anyone dealt with this? A modified mask would technically decrease its value as an FD lens, but it increases its value for use on a DSLR.

I don't think I can return the lens to KEH, even though they have a bayonet version that should have the later mask and I would be willing to trade up.

Any insight or references to this issue would be greatly appreciated.

Have Fun,

[gasrocks]

There is an article (linked to on many sites) "Homemade Fd-eos adapter." Email the author - nice guy with a lot of experience adapting fd lenses to work on eos cameras. My fd lens (which I use on an adapter) does not have such a flange as yours.

[ron chappel]

I've heard of someone cutting out that very part you are talking of Rick.
Unfortunately i can't remember any more than that...perhaps it's now an archived thread on photo.net?

In any case it would be quite easy to do as you say.
If you want to try doing it while the part is still attached to the lens,first cover the rear elements with tissues for protection.
Try to take it out though.
It might be easy (a couple of screws) or could be a real pain (FD mounts are really complicated to reassemble)

[Tom W]

You get 14 days to return at KEH, I believe.

Other than that, you will probably need to devise a way to protect the lens while you grind away with your dremel tool. Can the rear mount piece be removed to make modifications easier?

[CoolToolGuy]

You get 14 days to return at KEH, I believe.

Other than that, you will probably need to devise a way to protect the lens while you grind away with your dremel tool. Can the rear mount piece be removed to make modifications easier?

I didn't know about the return period on used lenses - this one was freshly reduced as well. It would be a shame, as this one is in really outstanding shape, with the case and all of the supplied filters. I may give them a call tomorrow.

The mask is the farthest-back piece of sheet metal on the lens, and it has several pins that signal things to the FD body (max aperture is one, I think). It also has slots in it for the two aperture levers. After looking at it again, I'm not sure I want to try to remove it. I bought an 'FD Lens Repair Manual' on CD via eBay, so I thought that would help, but is only for selected lenses, mostly WA and normals. There is plenty of room to stuff something in the barrel to protect against 'dremel dust', but I would want to angle it up so gravity is my friend and the grindings fall away.

I'll check with KEH and see if I can trade up.

Have Fun,