An unusual Canon mount

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

The other day I was playing with the newly arrived lenses, when one of them refused to go into the adapter. This happens sometimes when an FD adapter is taken off while still locked, but it was the case here: when I flipped the lens it turned out that the automatic aperture lever is enclosed in some sort of a protective shroud.

It was definitely of Canon's making.

I thought for a bit about how to deal with it, and decided to go with the brute force - in the worst case scenario I'd need to replace the mount, and I've got some potential donors. Well, I did not even need to be all that brutal - it popped out almost right away - as you can see it was held in place by a notch and a dab of glue. The lens can be used now, and I saw something I haven't encountered before.

kypfer · Joined: 27 Sep 2017 Posts: 514 Location: Jersey C.I.

aidaho · Joined: 29 Apr 2018 Posts: 456 Location: Ukraine

Never seen something like that before. What was the lens model?

DigiChromeEd · Joined: 29 Dec 2009 Posts: 3462 Location: Northern Ireland

The adaptor you removed is a Canon accessory for it's FD lenses. It is fitted over the aperture lever so that when the lens is reverse mounted on a camera for macro photography the aperture can be opened and closed manually using the aperture ring.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

DigiChromeEd · Joined: 29 Dec 2009 Posts: 3462 Location: Northern Ireland

Alsatian2017 · Joined: 05 Mar 2018 Posts: 237

Alsatian2017 · Joined: 05 Mar 2018 Posts: 237

fdlenses · Joined: 15 Mar 2017 Posts: 56 Location: Germany

Canon called this little thing a "Manual Diaphragm Adapter". New FD lenses – except for dedicated macro lenses – did not have the aperture lever lock switch or lock position which some of the breech-lock FD lenses still had.

The cap with a hole was called a "Macro Hood". There were two versions of it: One with a pin on the inside that enabled manual aperture control (second picture, left-hand side, pin at 12 o'clock position) and one without (second picture, right-hand side). To attach it, the hood with the pin has to be rotated counter-clockwise a bit (that's the direction of actuating the aperture lever) before it slips into the lens mount and is fastened clockwise as any cap. That's why it has the second marking at the 5 o'clock position.

While the hood can only be used with reversed lenses, the Manual Diaphragm Adapter can also be used for enabling manual aperture control with uncoupled extension tubes/rings.

Gardener · Joined: 22 Sep 2013 Posts: 950 Location: USA

Lightshow · Joined: 04 Nov 2011 Posts: 3669 Location: Calgary

Is it glue? Or was some gunk dried on it?
I actually never seen this accessory before, I have seen the reverse hood long time ago, interesting...
I know the SSC and earlier FD's typically have an aperture lever detent that will hold the lever in the engaged position which activates the aperture ring, to my knowledge the nFD lenses don't have this feature.