back-focus discrepancy: Leica/Russian

[FrankS]

Can someone help me out with this issue. I've read that the Leica standard lens flange to film plane distance is 28.80mm and that the Russian camera and lens specification is different. This results in problems only with longer lenses and when shooting at large apertures, due to less depth of field.

Does a Russian spec lens on a Leica spec body tend to focus closer or farther than indicated in the rangefinder? (assuming rangefinder is properly adjusted for Leica spec lenses)

I assume then that a Leica spec lens on a Russian body would be the opposite?

In which case can the discrepancy be rectified with a simple paper shim between the lens and the body? Is it the Leica lens on Russian body or Russian lens on Leica body?

(Bessa CV = Leica spec)

 

[Sonnar Brian]

A lot of conjecture on the Web, seems to bear out on my Russian lenses: The Russian camera is built to the Contax 52.3mm standard, hence the reason a J8 can be had in both Kiev mount and Russian LTM mount. So when you mount and focus a 52.3mm(Russian lens) lens on a body that the RF expects a 51.6mm (Leica Standard) lens, the lens is too close to the film and the focus is beyond what is indicated by the RF. This is what happens when a Sonnar (52.3mm) is mounted on a Nikon (RF calibrated for 51.6mm). I used shims to back off the mount by an edditional 0.5mm and calibrated everything at 8feet. It is not a perfect solution because the helical is slightly different between a 51.6mm lens and a 52.3mm lens, but it works good enough to use the 13.5cm lens wide-open and close-up.

I would not shim a Leica to use Russian lenses, but I have built up the RF cam using copper tape.

 

[rbiemer]

Frank,
According to Mr. Maizenberg's book "...all modern 35mm cameras with rangefinders(except Kiev)are equipped with one of the following lenses: Industar-50,Jupiter-8, or Industar-26m with the same working distance of 28.8 +/- 0.02mm .(emphasis mine) All the interchangeable optics have the same working distance"
That's the theory anyway. As we all know the FSU gear is sometimes better in theory than in practice.
There are two distances to consider: Body working distance and Lens working distance.
Ideally they are the same.
The 28.8 distance is measured on the body from the lens mount to the pressure plate-optimally with film in place. His (Maizenberg's) method seems to be to measure at each point on the mount where it is screwed into the camera body.
Presumably your leica spec body is correct and the lens is slightly off?
If it's one lens I think a shim might work--if that's the direction the lens needs to be adjusted.
If it's all or most lenses then the mount ring may be adjusted to compensate?
He (Maizenberg) does say that the order to check is: Rangefinder then Body working distance then Lens worknig distance.
Hope this helps.
Rob

 

[Roman]

I can confirm what Brian says - if I focus the Jupiter-8 on the Bessa (wide-open & close) on the eyes, it is usually the ears that are in focus (not the nose...)

Roman

 

[Paul Connet]

Re: back-focus discrepancy: Leica/Russian

Can someone help me out with this issue. I've read that the Leica standard lens flange to film plane distance is 28.80mm and that the Russian camera and lens specification is different. This results in problems only with longer lenses and when shooting at large apertures, due to less depth of field.

Frank, a difinitive discussion of the supposed incompatibility of Leica and FSU cameras and lenses can be found at Dante Stella's website:

http://www.dantestella.com/technical/compat.html

It is way too mysterious for me. I just put the FSU lens on the Leica body, shoot pics near and far, wide open and stopped down. If it works, I'm happy. If the pics are bad I try not to repeat that particular combination again. Quite surprisingly, a lot of times the two brands go together nicely, and I'm mostly happy.😉 I have a lot of FSU stuff and Leica too.

Regards, Paul C.