Just another Jupiter 8 collimation thread

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alexandru_voicu

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Hi everyone,

This is my first post here, but I am a long time reader of RFF. I'm very glad my account was finally validated.

This is my story. I have Bessa R2A and a bunch of FSU lenses (three wonderfully preserved Jupiter 8 and one NOS Industar 61). For quite some time, I started contemplating the idea of collimating them. I tested my favorite lens from the bunch (a 1971 black Jupiter 8, export variant) and I discovered it back focuses a few centimeters at 1m@f2 and that infinity focus is correct. As far as I understand how the rangefinder cam work, if I shim for close focus, I would definitely lose the inifinity focus. The "ideal" Jupiter 8 should back focus both at 1m and at infinity, so that a proper shim would fix the focus across the range. So, my question is, why not starting by first reducing the focal length of the lens and then shimming it accordingly? What do you think?

I would greatly appeciate your comments on this.

Thank you,
Alex

PS Brian, you are a worldwide celebrity! 🙂
PPS Please excuse my not-so-good English.
 
Alex- , welcome to the forum. On the PPS- if only I could master a second language as you have done with English...


The ideal situation is to reduce the focal length of the lens to the Leica standard. The problem is getting the room to move the rear group of the Sonnar in closer to the front group. You need to file down the rear of the mount, and polish down the front of the optical fixture used to hold rear group. It is very close to the Aperture mechanism. There is no secondary stand-off shim for the rear group, as there is with many Helios-103's.

I've reduced the focal length on a couple of J-3's, but ones where the focal length is on the high-end of "normal". This can be done with the earlier J-3's, where the rear module unscrews. I have not done it on a J-8, but the same technique works.

I rely on the "infamous" Sonnar focus shift to compensate for infinity focus after a lens is optimized for use close-up and wide-open. Most of the J-3's and J-8's will focus at infinity with the lens stopped down to F2.8.
 
Hi Brian (and everybody else reading this thread),

Thank you very much for your comments. I guess I will never be able to have "the perfect J8", so I'll start by shimming it first. I've read all your previous posts and I'll use a 0.1mm shim first. I hope the focus shift will do its job for what infinity is concerned. 🙂

The bad news is that my girlfriend just got her Bessa R3A (new) and the rangefinder is miscalibrated. While all my FSU lenses reach infinity on my R2A, they all don't on her R3A. I've tried them with my ltm adapter and my lenses. I'll try to calibrate it tomorrow, but my eyesight may be misleading me, which is very frustrating.

Please excuse my lamentation. 🙂

Best regards,
Alex
 
Depending on what adapter you use, the infinity focus on the Bessa might change slightly. Check her camera with an m-Mount lens if you can. I bought several inexpensive Chinese adapters for 50mm. Some do better than others. I've found that I-61's and later J-8's seem to call my 5m test target a 6m target, according to the distance scale. I put them on the adapters that are slightly too thick, problem solved.
 
Hi again and thank you for your replies.

Brian, we (me and my gf) both have voigtlander adapters, which are supposed of being higher quality. On my Bessa R2A, all my J8 lenses reach infinity on the rangefinder patch. So I took out my voigtlander adapter and my lens and I tried them on the R3A. In other words, the only real difference beeing the camera bodies. The patch on the R3A does not reach infinity, not even close. I think it's pretty obvious that either the R2A or the R3A is mismatched as they don't respond the same. I placed my bet on the R3A and I hope I won't regret it.

buzzardkid: that's great! things are now different from what they were in 1991. by the way, at that time I was in 6th grade. 🙂 If you ever plan to pay one more visit, drop me a line, it would be nice to meet a fellow rff member.

The conclusion of the evening is that unfortunately I have to postpone the collimation of the J8 in order to fix the newly acquired R3A. Please wish me luck.

Best regards,
Alex
 
It sounds like the R3a is off. If you do the adjustment yourself, this would be a good forum to post instructions.

On Rangefinder cameras and lenses: sometimes they will drive you crazy. I have a Canon III that I use for collimation work, and two Canon P's for use. Each will focus accurately with actual focus, distance scale, and rangefinder all agreeing with most lenses. THEN I will get a J-3 collimated for the Leica standard, and it will give slightly different results between the Canon III and the Canon P. Maybe the lens rotates to a different position, the RF Cam is not completely parallel to the mount???? So I end up just using the lens with the camera that it agrees best with.
 
Hi Brian,

Thank you for your support. Today I did my best to calibrate the R3A rangefinder. It's much better, but not perfect. I used the instructions found here. Because I paid so much attention to the rangefinder at infinity and because I used my glasses for the first time while focusing, I discovered that my R2A is also slightly misaligned both horizontally and vertically. I'm very depressed. I have to warn you, however, that I'm on those people who will ALWAYS find something wrong with any object, no matter how insignificant the defect is. I haven't touched a Leica my entire life, but I'm sure I'll find something wrong with it that even the owner would not be aware of. 🙂

Brian Sweeney said:
I've found that I-61's and later J-8's seem to call my 5m test target a 6m target, according to the distance scale. I put them on the adapters that are slightly too thick, problem solved.
Click to expand...

Is this just an example of wrong engraving of the distance scale or does the lens actually focuses at 6m instead of 5m (back focus)?

I'll keep you updated on both my first roll with the R3A and the Jupiter 8 collimation.

Best regards,
Alex
 
The error with the I-61 and J-8 is that the Distance Scale does not agree with the RF. The lens has a mechanical stop for infinity, the distance scale reads infinity: but the Rangefinder of the camera does not reach infinity. When this happens, I build up the RF cam with Copper tape so that the RF and Distance scale agree on infinity, then shim the actual focus to agree with both.

An example in this thread:

http://rangefinderforum.com/forums/showthread.php?t=91163
 
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