Canon LTM Lenses on Russian FED cameras

RalfJ · Sep 15, 2023

Hello -

I received a Canon 135mm 3.5 LTM lens that won't mount on either of my FED 5B cameras. I suspected that the rangefinder arm was getting in the way and I was correct. I put the shutter on B and mounted the lens by suppressing the rangefinder arm from the back and I was able to complete the mount. Is there a right way to do this without resorting to these extreme methods? Leica lenses and Industar lenses do not have this issue as their rangefinder driver is circular. Please see photo for reference. Many thanks for your responses.

reddesert · Sep 15, 2023

Not really. It is generally telephoto lenses that have this issue of the "tongue" rangefinder cam - other telephoto lenses besides Canon sometimes have it. Normal and wide angle Canon lenses usually have a rangefinder cam that goes all the way around and don't have the issue.

The Canon RF camera bodies have a circular RF feeler that is free to rotate, but the Russian RF bodies have a feeler with curved surface, with a pointy end that jams on the end of the lens's tongue RF cam when you mount it.

The RF cam calibrations are generally said to be different between Canon/Leica/Leica-copies, versus Russian Leica-thread RFs. The focus offset goes as the square of focal length, so in principle it is pretty negligible for wide angles, possibly noticeable for fast normal lenses, and significant for telephotos. This means you might be happier with a Jupiter telephoto on a FED body, anyway.

RalfJ · Sep 15, 2023

Many thanks for the info, i guess this lens will be dedicated to IIIB and the Canon 7

nosmok · Sep 16, 2023

Apologies if this has been asked and answered many times, but: having read about this RF-basis issue for years between Leica and Soviet cameras, it's still the case that any LTM lens should scale-focus accurately on any LTM camera body, correct (assuming that lens and body are set up correctly)? It's just a problem with the optical rangefinder itself...

RalfJ · Sep 16, 2023

nosmok said:
Apologies if this has been asked and answered many times, but: having read about this RF-basis issue for years between Leica and Soviet cameras, it's still the case that any LTM lens should scale-focus accurately on any LTM camera body, correct (assuming that lens and body are set up correctly)? It's just a problem with the optical rangefinder itself...

RalfJ · Sep 16, 2023

I think that zone focusing would be the safest route to go. I mounted a Summitar 50 on the Fed 5b and rangefinder was great on infinity. I then mounted an industar-26 that i had just cleaned and relubed, and it was perfectly aligned to infinity when checked with ground glass and magnifier through the focal plane where film travels, but was off with the actual built in rangefinder. So i just slid off the name plate and adjusted rangefinder to this lens. Very easy to do, but goes to show you that it is never a one size fits all between LTM based cameras.

reddesert · Sep 16, 2023

nosmok said:
Apologies if this has been asked and answered many times, but: having read about this RF-basis issue for years between Leica and Soviet cameras, it's still the case that any LTM lens should scale-focus accurately on any LTM camera body, correct (assuming that lens and body are set up correctly)? It's just a problem with the optical rangefinder itself...

In principle yes. The flange to focal plane distance is the same across the M39 mount, but the RF camming is marginally different. The way that these interchangeable lens rangefinder systems work is: there is one fiducial focal length lens, typically a "50mm," where the lens cam surface is just part of the barrel holding the optical elements and moves in/out with them as the lens is focused. The body RF feeler touches this cam and moves the RF element accordingly.

For all other focal lengths, the lens has to pretend to the body that it is the fiducial focal length: the lens RF cam is on a separate helical so that it moves at a different rate than the lens elements. When for example a 100mm lens is focused to 5 meters (extension 2.0mm), its RF cam has to extend only as much as the 50mm lens would extend when focused to 5 meters (extension 0.5mm). It is pretty easy to see for yourself how the cam extends less than the lens elements in a tele lens. For a wide angle lens the cam has to move at a faster rate than the lens elements. You can also see how this system limits focusing accuracy with long focal length lenses.

The difference between Leica/Canon and FED/Zorki is said to be in the fiducial focal length, one of them is set up for about 51mm and the other about 52mm. Not much, but enough that when the extension gets significant, it can't be covered up by depth of field.

Because the difference is all in the expected rate of cam motion, the focusing scales on the lenses should be unaffected by it (to the degree that focusing scales are accurate anyway).

nosmok · Sep 17, 2023

Thanks for these answers, RalfJ and reddesert. Always wondered about this, plus I have been thinking to modify a Zorki-3m by removing the rangefinder (making a "Zorki-1mf", ala a Leica If). It's good to have more data that doing so would accomplish what I need.

henryvk · Sep 18, 2023

nosmok said:
Thanks for these answers, RalfJ and reddesert. Always wondered about this, plus I have been thinking to modify a Zorki-3m by removing the rangefinder (making a "Zorki-1mf", ala a Leica If). It's good to have more data that doing so would accomplish what I need.

There's also the Zarya, which is a FED without a rangefinder to begin with: https://camerapedia.fandom.com/wiki/Zarya

Removing the RF arm from a FED or Zorki should be easy enough though.

Maybe also look at this thread here: https://www.photrio.com/forum/threa...ameras-with-leica-mounts.194081/#post-2587773

Kodachromeguy · Sep 18, 2023

reddesert said:
In principle yes. The flange to focal plane distance is the same across the M39 mount, but the RF camming is marginally different. The way that these interchangeable lens rangefinder systems work is: there is one fiducial focal length lens, typically a "50mm," where the lens cam surface is just part of the barrel holding the optical elements and moves in/out with them as the lens is focused. The body RF feeler touches this cam and moves the RF element accordingly.

For all other focal lengths, the lens has to pretend to the body that it is the fiducial focal length: the lens RF cam is on a separate helical so that it moves at a different rate than the lens elements. When for example a 100mm lens is focused to 5 meters (extension 2.0mm), its RF cam has to extend only as much as the 50mm lens would extend when focused to 5 meters (extension 0.5mm). It is pretty easy to see for yourself how the cam extends less than the lens elements in a tele lens. For a wide angle lens the cam has to move at a faster rate than the lens elements. You can also see how this system limits focusing accuracy with long focal length lenses.

The difference between Leica/Canon and FED/Zorki is said to be in the fiducial focal length, one of them is set up for about 51mm and the other about 52mm. Not much, but enough that when the extension gets significant, it can't be covered up by depth of field.

Because the difference is all in the expected rate of cam motion, the focusing scales on the lenses should be unaffected by it (to the degree that focusing scales are accurate anyway).

Thanks for an excellent description.

In my case, Brian Sweeney adjusted a Jupiter-8 to work almost perfectly on my Leica IIIC at all distances. But I have not used it wide open close-up, where it may back focus a bit.

aw614 · Sep 18, 2023

I could have sworn I read on rangefinderforum since the FSU rangefinders have a minimum focus adjustment, it is possible to adjust the rangefinder to the Lecia specification.

I zone focused my Zorki 1 when I had my Canon 35mm F2.8 on it and for the most part photos came out fine. I was mostly shooting at higher apertures, F5.6, F8

nosmok · Sep 18, 2023

henryvk said:
There's also the Zarya, which is a FED without a rangefinder to begin with: https://camerapedia.fandom.com/wiki/Zarya

Removing the RF arm from a FED or Zorki should be easy enough though.

Maybe also look at this thread here: https://www.photrio.com/forum/threa...ameras-with-leica-mounts.194081/#post-2587773

I had a Zarya for a bit. The Zorki-3m is pretty much the only FSU camera body to meet the criteria I have: full shutter speeds 1- 1/1000, in the correct order (1/30 not off on the other side of the galaxy), on one dial; easier loading than Leica (go ahead and call me a wimp-- I HATE the bottom loading thing). Still to be seen is whether I can get the knobs to sit a little lower on the top deck after the RF/VF window is gone-- on the 3m some shafts are quite tall to clear it, and the body is already slightly bigger than a Leica If, which is my model for this project and a really fun camera until you have to load it.

henryvk · Sep 18, 2023

I was wondering about that too.

nosmok said:
I had a Zarya for a bit. The Zorki-3m is pretty much the only FSU camera body to meet the criteria I have: full shutter speeds 1- 1/1000, in the correct order (1/30 not off on the other side of the galaxy), on one dial; easier loading than Leica (go ahead and call me a wimp-- I HATE the bottom loading thing). Still to be seen is whether I can get the knobs to sit a little lower on the top deck after the RF/VF window is gone-- on the 3m some shafts are quite tall to clear it, and the body is already slightly bigger than a Leica If, which is my model for this project and a really fun camera until you have to load it.

Are you planning on removing the RF/VF + housing? Now that I want to see when it’s done

Canon LTM Lenses on Russian FED cameras

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