FSU Lens on Leica LTM: backfocus problem

[Karlov]

hello everyone,
I'm new of forum and I know my question is not a new one but I cannot find a thread answering my doubts.
I own a Jupiter 8 black version and I got a Leica IIf.
Trying to mount it on Leica IIf I notice lens cannot reach infinity as is to say rangefinder is not completely aligned even when lens distance scale stops to infinity.
Despite that, trying to take photos at maximum aperture setting lens to infinity aperture doesn't show any focus problem.
On the contrary, if i try to focusing accurately test chart 1 meter away from camera I got a very strong backfocus.
I tried also an Industar 61 and an Industar 26 on Leica and all of them show backfocus (Industar 26 being closer to correct focus).
So my question is: there is a way to adjust or calibrate FSU lens to operate correctly on leica LTM?

Thank you in advance for your answer

 

[Dez]

First of all, does the lens screw all the way in properly? The infinity index should be straight up or a little bit past the vertical position when it is screwed all the way in. There is sometimes a slight incompatibility in the screw threads that causes that problem.

Any FSU screwmount lens should work correctly with your rangefinder, especially at distance. Are you sure the rangefinder is set correctly? Have you checked it against a known good lens from Leica or Canon, for instance? If both FSU lenses indicate the same thing, almost certainly your rangefinder needs adjustment.

This is very easy to do; all you need is a small screwdriver, 2-3mm wide. Undo the screw just beside your viewfinder window. Underneath it is another screwhead. Turning this screw very slightly will adjust the horizontal position of your rangefinder moving image. Set the lens to infinity and adjust the rangefinder for correct position when looking at an object at least 100m away.

It is fairly common for an FSU lens to need internal adjustment to focus accurately according to the rangefinder at close distances, but it is very unusual for the rangefinder cam in the back of the lens to be out of position, causing problems at infinity.

Cheers,
Dez

 

[Karlov]

Many Thanks for your suggestions. I have no opportunity to check fsu lens against canon or leica lens. I think I'll try to repeat test wityh Industar 61. Anyway, there is a manual or tutorial on line to read instructions to align rangefinder on Leica ltm?

 

[Dez]

Please read the third paragraph of my post above. It is as simple as that. The screw covering the adjuster is immediately to the right of the viewfinder window on the front of the camera.

Cheers,
Dez