A customer of mine brought in a HUGE 400mm Canon lens. The mount appears to be some sort of T-mount, but I can't tell exactly. They want to mount it to a Canon T50 body, but I can't start looking for an adapter until I can identify the mount.

A picture of the lens can be seen at:

http://photos.yahoo.com/shuttermutt in the "Canon Lens" folder.

Any help would be sincerely appreciated!

-Shuttermutt

By rick oleson on Thursday, November 15, 2001 - 11:00 am:

I'm not sure, but the rear cap on the 'accura' extension ring looks like an M39 thread as was used on the Canon and Leica rangefinder cameras. It might be that this was made for use on a reflex housing and the 'accura' tube would adapt it for use directly on the camera body (which would not be a promising proposition on a rangefinder camera). I don't see anything that looks at all familiar from Canon SLRs in the photo.

rick =

rick_oleson.tripod.com

By Shuttermutt on Saturday, November 17, 2001 - 09:51 am:

The customer also reported that the person they bought it from had two Canon rangefinders and two Canon SLRs for sale. I think the all of those tubes and other bits were used to convert the lens to be used on those rangefinders.

What I'm wondering, however, is if there might be an adapter setup available to mount the lens to an FD body such as an AE-1. I've seen T-mount to FD mount adapters, but I don't know if they'll work or not since I'm not sure if the lens is a t-mount or not.

-Shuttermutt

By Winfried on Sunday, November 18, 2001 - 02:25 am:

Take a caliper and measure the outer diameter of the thread. If it's 39mm, it's a Canon/Leica rangefinder mount. If it's 42mm, it is probably a T-mount (which has the same diameter, but a different thread pitch as M42/Praktica/Pentax mount).

I would guess that it's a T-mount lens, since there were very few lenses above 200mm manufactured to be used on a mirror box with a Leica/Canon rangefinder.

A T-mount to FD-adaptor will work mechanically, but of course you will loose the open aperture measurement feature. I think you will have to close the aperture of the lens to the selected value when measuring with an FD body.

By Shuttermutt on Monday, November 19, 2001 - 06:55 pm:

Well, my calipers tell me it's 39mm. The kicker is that what I'm measuring appears to be an adapter and NOT a part of the actual lens. The lens itself uses a thick two-bladed bayonet type mount. Think K-mount, but with two blades and REALLY beefy.

As the picture (kind of) shows, the whole assembly goes like this...

1. Lens (female bayonet with a rotating ring to lock the male piece in place)
2. Thick brass adapter (male bayonet on one end and 39mm male threads on the other)
3. Black aluminum tube (female 39mm threads on one end and male 39mm threads on the other)
4. Silver aluminum cap (female 39mm threads)

What's killing me is I can't figure out or find anyone who knows what that monster bayonet mount is called. If I knew, I might be able to find a "mystery mount" to FD adapter of some kind.

You guys nailed what the lens has been adapted to mount to. Now I've got to find out what that actual lens mount is called. It's KILLING me! I can supply additional (smaller) detail pictures of the back of the lens if anyone wants to help play Sherlock.

Thanks for the help to date, guys!

-Shuttermutt

By Shuttermutt on Monday, November 19, 2001 - 06:57 pm:

Correction...

1. Lens
2. Thick brass bayonet adapter
3. Black metal threaded ring (anti-seize ring?)
4. Thin M39 to F39 ring
5. Black tube
6. Silver cap

-Shuttermutt