Exakta lenses - ?

[martyn_bannister]

Hi all,

Can someone tell me what the deal is with Exakta (Exa?) lenses? I have bought a Triotar 135/4 (for which I think I paid too much) and a Flektogon 35/2.8 (for which I think I paid too little) and there is NO WAY either of these lenses will get even NEAR infinity focus on either of my Canons.

I have tried manually holding both lenses up to both my 10D and my 5D and they are both MILES away from focus even when stuffed as far into the camera as they will go, never mind trying to miss the mirror on either body.

Is there a difference between EXA and EXAKTA mounts and are there some lenses/mounts which WILL focus to infinity on a Canon and some that WON'T???

Or am I doomed to near focus shooting or selling them again?

Any help appreciated.

[RioRico]

This is very curious. Do these lenses have simple bayonets, or do they have the stop-down button sticking off the side? I say it's curious because of these lens registers (flange focal distances):

Canon EOS: 44mm
Exakta/Exa: 44.7mm
Pentax/M42: 45.46mm

Longer register lenses should achieve infinity focus on shorter register cameras. I have worked up a simple conversion that lets me obtain infinity focus with Exakta lenses on my PK-mount Pentax K20D -- I remove and save the tiny protruding screw from the Exakta mount and glue an M39-M42 adapter ring around the bayonet. I have grioud 0.8mm from the flange of a cheap infinity-focus M42-PK adapter. I screw the slightly adapted Exakta lens into that modified adapter, and infinity focus is mine!

I don't mess around with EOS cams so I'm not familiar with M42-EOS adapters, but a similar approach should work. Are you *sure* that these are Exakta-mount lenses? Pictures might help. Good luck!

[woodrim]

You actually have to hold it .7mm farther out , not stuff it in. Exacta is a relatively small mount.

[martyn_bannister]

[luisalegria]

As I understand it there are plenty of Exakta-Canon adapters available.

Because the Exakta and Canon register distances are so close, the adapter maker has to be careful of tolerances. It is easy to make one that is too thick. Some Exakta-Canon adapters don't give infinity on some lenses, particularly wide angles, because they are a bit too thick.

There were some posts here some time ago about "shaving" some adapters to fix that problem.

[martyn_bannister]

[luisalegria]

There is only one other Exakta mount, the uncommon external bayonet seen on some large lenses. Most Exakta bodies have the external flanges for these. And there are no commercial adapters for the external bayonet, though I have made one for a Meyer 300/4.5

For certain your lenses don't have this mount.

But other than that an Exakta mount is an Exakta mount. I have used Exaktas for 30 years and I haven't seen any lenses that have anything significantly different.

You may be getting something wrong by holding your lenses up to the lens opening. Why not try an adapter ?

[martyn_bannister]