weird spot with J-12

[ath]

Hi folks,

I bought a '59 Jupiter 12 in LTM. The lens is in OK shape; the glass has some cleaning marks but is not too bad.
My first roll turned up that a strange spot appears exactly in the middle of the frame. With a second roll I did some systematic testing and came up with the following results:
1. The spot is strongly affected by aperture - very dominant at f/11, dominant at f/8, nearly gone at f/5.6 or below.
2. The spot is NOT affected by UV filter, focus, shade or re-blackening the rear element.
3. The spot is ALWAYS exactly in the middle of the frame.

example taken at f/11:

Any ideas how to get rid of this? Camera is a M2 and OK.

 

[pevelg]

I used to have this problem with one of my Russian lenses, though I don't remember which one. I had always thought that the problem was due to lighting conditions, but I never was really sure. I'm not much help here, but I have experienced what you are experiencing. Perhaps comfort from knowing that you are not alone? 🙂 I remember shading the lens with my hand in an attempt to remedy situation, but I don't recall if it worked. I've sold all my Russian lenses a while back....

 

[oscroft]

I had the same problem with a J-9 some time ago but never found out the cause - I eventually gave it away for spares. (A second J-9 was, and still is, fine)

 

[OldNick]

This seems to illustrate another reason to buy late-year FSU lenses. I have a 1987 J-12, purchased from Yuri at Fedka, and it has none of this type of problem.

Jim N.

 

[xayraa33]

I would like to see a tutorial on re- lubing the LTM J-12.
someone must have done this themselves at sometime.
it would be a great sticky.

 

[ath]

f2eyelevel, I will check if the glass is oily. I hav already disassembled the lens to replace the shim (focus was off 10cm at 1m). The rear element is easy to unscrew; the front group comes off after detaching the focus ring and screwing it out with a spanner. Blades looked dry but I will check once again.

xayraa33, when you habe disassembled the lens like above you hold the focusing mount. Be careful when unscrewing it and mark the threads where to start. Mine was sticky as well and for a start (until I solve the spot problem) I just put four drops of very thin high quality oil on the helix (front / end / inner / outer thread) and turned a few times. Quite smooth now but probably not a long term solution.

 

[ath]

The glass and the aperture blades are clean 😕

 

[khadgar_959]

I also have kind of this problem on my J-12, just try to use in soft light like cloudy days or rain days. or if you have to use it in sunny days, it's greatest to take the photo in shades

 

[john341]

I use a J12 quite often on my Kiev and on my Leica. I have not seen this problem. I have seen a very similar problem with my FOCA camera. I put it down to a shiny spot on the rear of the lens assembly...looks very similar to your picture. Check rear of lens for any bright spot. Best of luck!