Help with 100mm USM Macro mount

[coolman23]

I borrowed a 100mm macro from a friend and can't get the thing to mount on my 20d. It sets in properly but won't turn or lock. Any ideas what the problem could be? Thanks.

[Greg_C]

Make sure that none of the screws on the rear of the lens are loose. One could be causing this ..... maybe. It is a EOS mount lens isn't? (silly ??? I know)

Oh. and welcome to POTN.

[SarahJD]

That was my first thought too -- is it a Canon mount?

[coolman23]

Hi,

Yes it's a Canon mount. I've been comparing this to my other lenses and for the life of me cannot see where the problem could be. Oh, and thanks for the welcome.:)

[snails]

Check to see if one of your other lenses will mount on the camera.
If both lenses will not mount double check the body, I'd look for a stuck latch, friction springs or any physical damage.
If your lens fits and the 100mm doesn't, compare the mounting hardware between the mounting lens and the one that will not. I would be looking for loose screws, or physical damage.

Can you tell I'm an engineer?

[SarahJD]

I don't have any other ideas -- sorry. Let us know if you figure out the problem. And I forgot my manners -- WELCOME! :)

Sarah

[coolman23]

Well it must be something with the mount that's off although it sure isn't very noticeable to the naked eye (at least not mine). I found an old Rebel x film camera that had the plastic receiving mount and it was able to fit on that with some but not much resistance.

Anyway, it looks like now I need to go and buy my own - which isn't a bad thing.