Jupiter 12 focus problems

Hello all,

I recently purchased a perfect looking contax-mount Jupiter 12 to use on a Kiev 4. Thumbnails of the lens follow:

I took some photos with it and was disappointed with the results. It seems to perform best at about 1 metre's distance and when focused on infinity the image is very soft. I'll put here 3 photos unprocessed scans, the first with focus on an object about 1 metre away, the second, with the focal point on a tree in the foreground and the third, on the buildings at infinity:

All three photos were at f/8 and the depth of field on this 35mm lens is (or should be) pretty generous. What might be going wrong here with the focus? I'm pretty certain that i mounted the lens correctly (body locked at infinity and lens focused at infinity before mounting. The camera also performs well with other Jupiter 8 5cm lenses that I have.

Thanks,

I've bought several Jupiter-12's that needed to be "shimmed", meaning the ring that controls the stand-off of the optical barrel within the focus mount had to be changed.

To test for this: take some shots of a ruler at minimum focus, and again at about 5m. Shoot wide-open. For a second test, shoot a brick wall or fence to test for de-centering.

The J-12 uses the same shims as the J-8. You can also make shims from paper, plastic, foil, etc. If the actual focus is too close, the shim needs to be thinner. If it focuses past what the RF indicates, the shim needs to be thicker.

Some shots of a J-12 that I sold. This one is Leica mount, but the shims are the same as the Contax/Kiev mount. The optics come off the focus mount the same way, unscrew rear group, then take front section out to expose the shims.

Leica - For Sale: Jupiter-12 Leica Thread Mount| Location: USA | Ships:

To test for this: take some shots of a ruler at minimum focus, and again at about 5m. Shoot wide-open. For a second test, shoot a brick wall or fence to test for de-centering. The J-12 uses the same shims as the J-8. You can also make shims from paper, plastic, foil, etc. If the actual focus is too close, the shim needs to be thinner. If it focuses past what the RF indicates, the shim needs to be thicker.

Thanks a lot Brian. When you say "take some shots", are you referring to a digital camera? I have only film cameras to test, a Kiev IV and a broken Conatx III. Someone told me once that an SLR focus screen can be placed on the film plane to test/adjust focus. Should this work? I have a screen from a Nikon F2. A question here about this: is it correct that the etched side of the screen should face downwards, ie. so that the etched side is placed on the focal plane? That must be right...

My Jupiter 12 is from 1958 and I've heard that these have a wider rear-group than later models. I also have a spare scratched Jupiter 8M from the seventies from which I can take shims if needed. Hopefully these are the same, but otherwise I can try cutting rings from tin as you suggest.

Should I also tests the focus at infinity or is it better to adjust for minimum focus and at 5m?

All the best!

The shims are exposed after unscrewing the front section of the lens, which may be done after the rear section is removed.

I've used scotch tape on an exposed piece of film, held flat with a piece of glass. An SLR screen will work.