Jupiter 8 and Leica

[MarkoKovacevic]

Should my Chrome J8, which focuses correctly on a Zorki 4, focus correctly on a Leica III?

 

[Roger Hicks]

Should. If it doesn't, the possibilities are (1) incorrect register, with errors cancelling out on the Jupiter and Zorkii or (2) cam on Zorkii adjusted to take account of of lens errors.

Personally, I incline towards the view that if it focuses perfectly on the one, it should focus perfectly on the other. This is more likely than either of the above scenarios.

Cheers,

R.

 

[Sonnar Brian]

The focus should be slightly off with everything else being correct on both cameras. The focal length of the J-8 is slightly longer than what the Leica is calibrated for. The J-8 has a nominal 52.4mm focal length, the Leica is set for a nominal 51.6mm. The difference in the throw of the lens is about 0.1mm. I shim my J-3's and J-8's for the Leica standard and optimize it for close-up and wide-open focus. I stop down slightly for infinity, the Sonnar focus shift works in your favor.

Adjusting the J-3:
http://www.ziforums.com/showthread.php?t=97

 

[ALEXFLEX]

A reliable camera, many features of the lens, this course was more fun

I hate regular camera repair

 

[MarkoKovacevic]

If the focal length being slightly different would be able to throw the focus off, would a CV lens be grossly focused?

 

[Sonnar Brian]

A CV lens is made for the Leica standard. Depending on the Focal Length, it may or may not focus accurately on a Zorki.

Putting a CV 50mm F1.5 Nokton on a Zorki can cause focus issues wide-open and close-up.

 

[MarkoKovacevic]

A CV lens is made for the Leica standard. Depending on the Focal Length, it may or may not focus accurately on a Zorki.

Putting a CV 50mm F1.5 Nokton on a Zorki can cause focus issues wide-open and close-up.

Hmm. I guess the only thing to do is try and see what happens. If it doesn't work out, the focusing ring needs a CLA anyways, so I could get it shimmed during the CLA.

 

[wolves3012]

I have one J-8 that I use on my IIIC, it's one that Kim Coxon adjusted specifically. Initially it was off-focus (front focussing, I think) and Kim adjusted the focal length rather than adjusting the shimming. I hadn't ever used it on an FSU but Kim did say it probably wouldn't have focussed correctly there either. Just so you know that shimming alone may not be the answer.

 

[julio1fer]

I've used occasionally two different J-8 lenses in my IIIb, without any noticeable problems.

 

[Sonnar Brian]

I have one J-8 that I use on my IIIC, it's one that Kim Coxon adjusted specifically. Initially it was off-focus (front focussing, I think) and Kim adjusted the focal length rather than adjusting the shimming. I hadn't ever used it on an FSU but Kim did say it probably wouldn't have focussed correctly there either. Just so you know that shimming alone may not be the answer.

I've done both. The rear element has to be moved in closer to the front group to reduce the focal length. The J-3 and J-8 do not have "secondary shims" that control the standoff. You have to polish down the fixture for the rear module and perhaps the main optics module to move it in. I've done this on two J-3's after adjusting the main shim was "just not good enough".

The results are good, lens is accurate close-up and wide-open, and at infinity.