Potential Problem with Jupiter 12 LTM

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Lawrence Sheperd

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I just received a late-model Jupiter-12 (serial no. 9009003, English "Jupiter-12"). Looks in great shape, and un-mounted the focus ring turns smoothly and easily as does the diaphragm. However, when I mount it on either my FED 2 or (carefully) on my Canon P, the focus movement becomes so stiff that the lens will unscrew when racking out the focus. I mount the lens with focus at its minimum distance.

Any thoughts?
 
try to set the camera on Bulb or Time exposure, push the shutter button, hold the curtain open, and install the lens.
As far as i know, a jupiter 12 should not be installed on canon P,
the issue is either the baffle in front of curtain not allowing you to install the lens, or if you managed to install it, once you focus to infinity, the large lens element will move back touching the baffle or shutter curtain.

My friend have 2 canon P and one canon 7 and when i try to install my black 1982 J12, the baffle will not allowing me to do it. A leica M, leica III series, Hexar RF, Rd1, is OK with J12. If J12 from 199x have smaller rear element it may fit, but is there any j12 like that?
 
I have seen that happen as well with some FSU lenses. Does it get better if the lens is screwed in almost, but not quite, all the way? My theory is that the combination of rather flimsy aluminum mount construction and sometimes optimistic tolerances in some of the Russkii lenses can translate pressure against the back of the mount into slight warpage which can cause tightness in the focusing.

Does it screw in easily and smoothly? If not, some slight binding of the threads can also cause warpage. I have sometimes been able to alleviate this problem a bit by polishing the lens thread a bit with fine steel wool, or a mild abrasive such as Comet cleaner.

Some FSU lenses are really great, but they can be a bit inconsistent.

Cheers,
Dez
 
Thanks for the responses. After doing some more searching on this site and others, it seems as though there may be some interference with the RF cam and the rear element barrel, causing the cam to rub slightly. Also, the lens' lubricant is probably stiffened. Some interior screws may also not be torqued equally. So many possibilities....!

As far as mounting on the Canon P, it seems that the majority of folks with the later black version (mine) say that the lens will mount 9 times out of 10. Hopefully mine is not the 1 out of 10. It appears the rear element and barrel are slightly smaller than the earlier black versions and the original chrome versions, also. I did not feel any undue pressure when mounting. However there is film in the camera so I could not verify (I know, stupid of me to try without being able to view from the rear of the camera.)

I'll give cleaning and re-lubing a try and then work out the kinks on the FED 2.
Much appreciation to those chiming in.

BTW, does anyone have the "how-to" that Mike Kovacs linked to on this APUG post? Link is a dead end now.
 
I just tried mounting my late model (black, 1981) Jupiter 12 on a canon P. There was plenty of clearance. Unfortunately, I only have one LTM Jupiter 12 to try at this time. I think I remember having a problem once with a J12 on a Canon 7 though.

Cheers,
Dez
 
Lawrence Sheperd said:
Thanks, Colyn. I wonder how different the construction of the contax mount (your link) is from the LTM mount (my lens?)
Click to expand...

The Contax mount is quite different from the LTM one, I'm afraid. If you're looking for re-lube instructions for the LTM version, I'm not sure they exist on the 'net. I have not come across them so if you do find something, please post a link.
 
Lawrence Sheperd said:
I just received a late-model Jupiter-12 (serial no. 9009003, English "Jupiter-12"). Looks in great shape, and un-mounted the focus ring turns smoothly and easily as does the diaphragm. However, when I mount it on either my FED 2 or (carefully) on my Canon P, the focus movement becomes so stiff that the lens will unscrew when racking out the focus. I mount the lens with focus at its minimum distance.

Any thoughts?
Click to expand...

I can't comment on the Canon P but the RF sensor arm on the FED 2 is commonly too low, which casues it to catch on the side of the rear element of a J-12. You need to mount it with the back off and the shutter held open on 'B' to verify if this is your problem. If that is the issue, the solution is simple: bend the arm upwards until it just clears. Obviously, be careful when doing this! It doesn't take much force. The distortion of the lens-mount mentioned by Colyn is also a potential problem, what he says is correct. If a lens runs freely down the mount threads though, it's not likely to be the issue. I've come across this particularly on the Zorki/FED 1 with the collapsible Industars, I haven't seen it happen with any other combinations but it certainly could.
 
Thanks much, wolves3012. I'll be sure and take photos and post them (if successful with the CLA.) I believe that I'll just dedicate the J12 to the FED 2 and try and find a reasonably priced Canon 35 for the P.
 
pb908 said:
try to set the camera on Bulb or Time exposure, push the shutter button, hold the curtain open, and install the lens.
As far as i know, a jupiter 12 should not be installed on canon P,
the issue is either the baffle in front of curtain not allowing you to install the lens, or if you managed to install it, once you focus to infinity, the large lens element will move back touching the baffle or shutter curtain.

My friend have 2 canon P and one canon 7 and when i try to install my black 1982 J12, the baffle will not allowing me to do it. A leica M, leica III series, Hexar RF, Rd1, is OK with J12. If J12 from 199x have smaller rear element it may fit, but is there any j12 like that?
Click to expand...

(I know the thread is old but if it can help anyone🙂

It is a bit of a lottery, but J-12 from 80s onwards have more chances to fit on Canons.
I researched before getting mine to fit in my digital Fuji X-E1 by reading about experiences with J-12 on Canon P and 7.
Mine is from 1986 and it fits.
If you look carefully to pictures of later Jupiter-12 before buying you'll see some with slightly smaller mushroom. Well, that's what I did.
Some will fit, some won't, but it seems that there is more chances when trying with 80s specimens.
To be exact after checking my notes: from 1975 to 1990, many specimens reported to fit.
 
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