NOS Jupiter 12 lens focus issues on Leica M

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Huss

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I 'won' a NOS Jupiter 12 off ebay. Serial # dates it as 1958 production. Chrome finish and really looks like new.
I put it on my M240 using the same LTM adapter that my Voigtlander 35 2.5 was being used just a moment earlier. The CV lens focuses perfectly.

I expected perhaps some focus issues, but the Jupiter 12 can only achieve focus between 1.5 to 3 ft!! Everything outside that range is out of focus. Initially I thought it may be an rf coupling issue so I used Live Focus.
This was at 2.8 (where it actually looked really good..)

Taking the lens off the camera, the focus ramp elongates and retracts smoothly as expected when focused from min distance to infinity.
So... any ideas? Outside send it back as it was sold "As Is".

Thanks!
 
Your optical cell is way too far out from the focal plane so any shims that could be missing would not be the problem. Shake the lens around near your ear to see if you hear any rattling. That may be a case of loose elements but probably not. You'd be able to see across the frame. This would be similar to decentering but if a group was perfectly centered and not completely tight then you'd have sharp in the middle and rapid sharpness falloff towards the corners.
These lenses, when working, are usually excellent performers.

Your problem is most likely that someone tried to lube up the old helicoid and got the alignment out of whack. This would effectively put the lens within a different range of focusing as you've described. If no obvious problems like loose elements are present, it's going to have to be taken down to bare helicals then, through trial and error, reassembled, as it really sounds like the focusing barrel is "inside" the stop screw that limits focus from ~3ft to infinity.
Good luck.

Phil Forrest
 
it is tightly screwed, and how do I tell if shims are missing? Nothing looks like it's missing.. it just looks new:

j121_zps5bwitqfi.jpg


j122_zpsqbuk6kjk.jpg
 
Phil_F_NM said:
Your optical cell is way too far out from the focal plane so any shims that could be missing would not be the problem. Shake the lens around near your ear to see if you hear any rattling. That may be a case of loose elements but probably not. You'd be able to see across the frame. This would be similar to decentering but if a group was perfectly centered and not completely tight then you'd have sharp in the middle and rapid sharpness falloff towards the corners.
These lenses, when working, are usually excellent performers.

Your problem is most likely that someone tried to lube up the old helicoid and got the alignment out of whack. This would effectively put the lens within a different range of focusing as you've described. If no obvious problems like loose elements are present, it's going to have to be taken down to bare helicals then, through trial and error, reassembled, as it really sounds like the focusing barrel is "inside" the stop screw that limits focus from ~3ft to infinity.
Good luck.

Phil Forrest
Click to expand...

Nothing rattly, nothing lose. Sounds like it needs to be stripped down and realigned..

A deal is only a deal if it remains a deal...

I paid $40 all in for it. The seller claimed to have gotten good results. I kinda want to get this thing to work, as the shots I examined wide open (in the range that it can focus) were really sharp. And this thing is so different from my other glass.

p.s. thanks for the advice everyone
 
When you put the lens on your Leica, did the rangefinder align with infinity at infinity? If so, then you don't need to strip the whole thing down (especially if the barrel turns smoothly.) It looks like infinity is properly aligned in your photo. Anyway, if your RF patch says it's at infinity, then you need to remove the whole optical/aperture block from the helicoid assembly. I forgot how this is done but they are two distinct assemblies as the Contax mount version can be perfectly transplanted into the LTM version.
If your camera's RF patch aligns at infinity, what you'll have to do is measure the physical distance from the mount to the end of the barrel at infinity then do the same at close focus.
If close focus is about 1 meter, then take the difference between your first two figures and you'll have to stack up that much shim material under the optical/aperture assembly. It's hard to diagnose without seeing it but from the looks of it, this is possibly what has been done.
Are there tool marks on the lens? It looks very nice and considering its age, could be a true German lens or at least one of the best versions of the J-12.

Phil Forrest
 
My J-12 is a bit older, 1956, and would front focus badly and would not focus to the infinity.
The whole optics had to be brought a few millimeters nearer the film plane and cost me almost what I paid for the lens.
I am told that the newer black ones are much better with this regards.
 
Yeah it aligns with the rf at infinity, but is way out of focus.
I also noticed large pieces of dust in there, so it looks like someone took it apart and bogarted it up. A couple are big enough that when I set the lens to f22 and 'infinity' they showed up as blobs on the image!

No tool marks on the lens. But it would have been better if there were and it worked properly!
Quite a bummer as the lens really looks like new, with not a cleaning mark or scratch on the glass. But hunks o dust in there! I love the size of it, and it looks cool too. From the test images that were in the focus range of 1.5-3ft, it is really sharp! Talk about a specialized lens...
 
J-12 butt and front (lens block) just unscrews. Watch it here. https://youtu.be/yRlAV599DXc
Shim comes out in this video as well. White metal ring.
Particles inside is normal for old FSU lens like this. It is paint.
Wrong, missing shim, might be wrongly assembled heliciod (I'm not sure about it). Or butt and lens block are from different lenses. Known dirt trick.

This lens is one the easiest to work on. My Rissian Biogon was with dry lube and flimsy. I re-lubed it, put back together, lens is firm and focus is as good as on Leica lenses.
 
Excellent video Ko.Fe, thanks for the link.
In the video the lens butt easily and quickly unscrews. Mine loosens up, then spins and spins w/o ever detaching. As if someone stripped the threads...
 
ckuwajima said:
My J-12 is a bit older, 1956, and would front focus badly and would not focus to the infinity.
The whole optics had to be brought a few millimeters nearer the film plane and cost me almost what I paid for the lens.
I am told that the newer black ones are much better with this regards.
Click to expand...

Yes, I've recognized this same issue with my copy. Shimming (in the standard way) does no good. The rear element has to be brought several millimeters closer to the film plane to achieve infinity focus.

I think it was re-assembled incorrectly. Gonna have to break it down to the helicoid as mentioned in an above post.
 
ok, disassembled the helicoid, and reassembled. it was fine.

it seems (as suggested) the butt of the lens (the massive rear element group) is not matched to the front optical group. if i unscrew the rear element approximately 1080 degrees, focus is correct.

so i think i'm going to attempt shimming the rear part with a rubber gasket or something. these are such hack-job lenses.
 
ckuwajima said:
My J-12 is a bit older, 1956, and would front focus badly and would not focus to the infinity.
The whole optics had to be brought a few millimeters nearer the film plane and cost me almost what I paid for the lens.
I am told that the newer black ones are much better with this regards.
Click to expand...


bayernfan said:
Yes, I've recognized this same issue with my copy. Shimming (in the standard way) does no good. The rear element has to be brought several millimeters closer to the film plane to achieve infinity focus.

I think it was re-assembled incorrectly. Gonna have to break it down to the helicoid as mentioned in an above post.
Click to expand...

I have a Contax/Kiev mount J-12 (black, 1980s) that behaves the same, and I agree that the solution should be bringing the whole lens block closer to the film plane. I just haven't got time to fiddle with it so I don't know the detailed way of how to fix it.

My best J-12 is a chrome Arsenal version in Contax/Kiev mount. Zero focus error.
 
Jupiter 12 for Kiev that I have came in just like that. The whole optical assembly needs to be moved back, not the shim. There is a screw, that fixes block in certain position. It has to be barely catching the slot in outer barrel. When reassembled, most people don't screw it in far enough. I don't have it in front of me, so I am going from memory. It took two or three tries, because it was never far enough.
 
I think that fixing screw might be the one on aperture mechanism.

Edit:

Now I remember. Once rear element is unscrewed, retaining ring is accessible. Removing it allows for lifting entire optical assembly out of focusing mechanism, including aperture adjustment ring. Optical block screws into aperture ring, with aperture adjustment screw acting as a stop. Most likely, optical block is not screwed in enough. It has to be screwed in far enough for the screw to be at the end of the slot in aperture ring. It should be half-in half-out. Reassembly is in reverse order. Check collimation on ground glass with shutter open, lens set on infinity, and a SLR.

Hope it was helpful.
 
Huss said:
Excellent video Ko.Fe, thanks for the link.
In the video the lens butt easily and quickly unscrews. Mine loosens up, then spins and spins w/o ever detaching. As if someone stripped the threads...
Click to expand...

Well, it was hard for me to believe what LTM J-12 from fifties is 40$. Now we both know why.
 
Yes... Maybe it was NoS all of these years because it was "Brak" from the factory. It means something went wrong during manufacturing, but still made it in the store. Very common for FSU times.

If you want it NoS and with better chances to be OK, look for black ones with sn starting with 91. Last year of production was 1991, if I'm not mistaken. I have one, briefly, for curiosity. It was never used before. And it was OK on Leica with original shimming, just little bit of front focus.

M4_2J12YFKent400HcB7M_June2016208.JPG


More pictures here:
http://rangefinder.ru/glr/showphoto.php/photo/91641/ppuser/9655/cat/500
 
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