Focus Jupiter 3 on M8

[jazzwave]

I plan to buy Jupiter 3 ( I love Sonar looks) for my M8 and M4P.

Need your information , Is there any focus problem this lens on M8?

regards
Ronni

 

[Sonnar Brian]

There are focus problems with most Jupiter-3's with any camera made to the Leica standard. This can usually be corrected by adjusting the lens via the main shim.

 

[dotur]

www.ivanlozica.com

And there is a more expensive way: J-3 in Kiev/Contax mount with Amedeo's Contax -Leica adapter.


0468dot2011 by dotur, on Flickr

 

[Mr_Flibble]

I found it's only a problem at close up with a large aperture where the slight back focus became visible

 

[Dez]

J3 on an M-Leica

J3 on an M-Leica

The J3 as it came out of the factory generally didn't focus properly even on contemporary FSU cameras, due to miserable quality control. Any example I have ever played with required re-shimming to be reliably usable. Fortunately, this is really easy to do, and there are loads of sites that show how.

There is a small difference between the default focal length of the FSU 50mm lenses and those made for Leica/Canon cameras, which theoretically makes it impossible to focus correctly over the whole focus range. It is possible to shift the focal length to compensate, but this is a considerably more difficult modification, and I doubt if it is worth it. Generally. I would consider it possible to shim a J3 more or less correctly for a Leica/Canon, or exactly for an FSU camera, but not both if you plan to use large apertures.

Incidentally, the shimming methods call for checking the focus at the film plane at whatever subject distance is most important to you using a ground glass or equivalent device. I use an old Exakta waist level finder. With its magnifier, I find it to be the easiest way to do this job.

The J3 is a very nice lens, and far cheaper than the astronomically-priced Leitz alternatives. Do the shimming mod- it is definitely worth the effort.

Cheers,
Dez

 

[Dez]

An example

An example

The discussion about the J3 got me off my backside this afternoon to check and adjust two lenses that I had put away some while ago as needing some service.

The first J3 is a silver one from 1967. It is cosmetically near mint, but I had previously found it did not focus accurately. I put it on my FED 2 to check the focus at the film plane with my trusty Exakta waistlevel finder. It was WAY off. With the scale set to infinity, it actually focused at 4-5m. The lens had a 1.36mm shim. It needed to be shimmed at 0.7mm to focus accurately. Much fiddling was required to accomplish that.

The second one is a 1977 black one bought as new old stock. I had not been using it at all as the coating is not as good as the older ones, and I already have too many lenses. That one had a shim of about 1.45mm, and is almost correct, but still focuses a bit short. I think I may be able to improve it by substituting the 1.36mm shim from the other one, but got lazy and just put it away. When you re-shim the lens you have to reposition the aperture ring, which is a bit of a pain. One of these days I'll get ashamed enough to finish the job.

Anyway, in my expereince, the J3 is really a very capable lens, but you really need to do the work that the factory didn't to realize its potential.

Cheers,
Dez

 

[Sonnar Brian]

The worst part of repositioning the aperture ring: tapping out new holes for the set screws. I use a triple-zero drill bit with a manual hand-drill.

 

[Dez]

The worst part of repositioning the aperture ring: tapping out new holes for the set screws. I use a triple-zero drill bit with a manual hand-drill.

Yes indeed! You can figure where the holes need to go easy enough, but I am always tempted to drill the indentation while the aperture ring is still attached, and unless I am super steady, I will just mess up the threads in the aluminum ring. I try to have the discipline to mark the spots properly and then take the ring back off for drilling. I have a lot of watchmaking tools, and I find a pin vice is the best tool for that work.

Cheers,
Dez.

 

[Sonnar Brian]

Today's Project.


Really nice 1967 J-3 shimmed for my M9. Wide-Open at f1.5.




And at F4:



My M9 gets used with Mostly Sonnars.

 

[Sonnar Brian]

My standard test for accuracy,

Fence post at F1.5.

 

[Dez]

Those are really sharp, Brian, and obviously focused correctly. I keep hearing that because of the slight focal length difference from the nominal 50mm of the Leica and Canon, that even a well shimmed J3 can't be corrected over the whole focus range on a Leica body without a challenging mod to shift the focal length. Is this just an urban legend? Or did you specifically correct at a close focal distance?

Cheers,

Dez

 

[Sonnar Brian]

Not urban legend, the Russian standard is a nominal 52.4mm and the Leica is nominal 51.6mm. Do the math, The J-3 requires a 0.1mm longer throw when moving from 3ft to infinity than does the Leica. I shim the lens for close-up and wide-open. The Sonnar focus shift works for you, stopping down shifts the focus towards infinity.

 

[Dez]

AHA! So sometimes you can catch a break! I just shimmed up a J3 on my FED2. I'll have to give it a try on a screwmount Leica. It certainly seems to be working properly for you!

Cheers,
Dez

 

[nksyoon]

Is the J3 for sale, Brian?

 

[Sonnar Brian]

I've posted this image before, but I just like it.

This J-3 is made from three different parts lenses. front element and focus mount from a 1983 Valdai lens, 1955 KMZ optics module with the two triplets, and aperture ring from a third Valdai lens parted out.

Wide-open on the M8.





I use a 1.25x magnifier on the M8, one of the Chinese finders available on Ebay. Put an O-Ring around the outerrim to protect my glasses.

I have a hard me letting any of my lenses go. They are all a little bit different.

The J-3 is very easy to work on.

http://pentax-manuals.com/repairs.htm

Kim Coxon, a Moderator here, has posted instructions for the J-3.