Jupiter 3 problem

[payasam]

On both Zorki 1C and Leica M2, the focus of my Jupiter 3 is off. When focus on the moon is right, the distance scale is somewhere between 20 metres and infinity. On the first roll in my recently acquired (from Youxin Ye) M2, I lost some potentially good pictures because the plane of sharpness was some 6 or 8 inches closer to the camera than what I had focussed on. Subject distance was a metre or so, aperture f/1.5 and f/2. My Jupiter 12 shows the same error at infinity, but in practice the focal length of 35 mm and the maximum aperture of f/2.8 save pictures from being ruined. On both camera bodies, an Industar 61 L/D and a Culminar 85/2.8 are bang on, and there is no problem in the photos taken with them.

I can get correct focus with the J-3 if I deliberately mis-focus, but I would much prefer to fix it. Trouble is, I have never opened up a lens and wouldn't know where to begin. Kind of hoping that a certain Brian reads this.

 

[photodog]

Here are the instructions:

http://www.pentax-manuals.com/repairs/j3service.pdf

You will need to adjust the shims between the lens assembly and the focusing mount.

Good luck.

 

[payasam]

Thanks very much. I mean, woof.

 

[payasam]

I don't have the tools, but that's a minor point. I don't have the skills. Will just have to accurately mis-focus to get focus right. Should be easy: did it (the other way) for 17 years with an M3.

 

[Kim Coxon]

Is the focus out throughout the range or just at close focus?

Kim

 

[payasam]

Kim, I don't yet know. I'm hoping that history will repeat itself, sort of. My M3's R/F was off by the same amount at all distances. In this instance the camera bodies are above suspicion (I think).

 

[Sonnar Brian]

You wrote that the actual focus was closer than what the RF indicated. That means the optics module is too far out from the film, and the shim needs to be reduced. There is also a variable stand-off ring on the optics module. IF it has been adjusted to add to the stand-off, you should be able to undo the set screws and screw it back in. You will need to check the actual focus with the M2 using the instructions posted on Kim's website.

 

[payasam]

Brian, I put a couple of bits of thickish paper between the J-3 and its M adapter. When mounted on the M2, the R/F images align at infinity. Will do a couple of test exposures in the morning. In the day, before the paper trick, I shot a few near range frames which were deliberately mis-focussed. The paper thing is hardly a solution even if it works -- after all, I shall need to use the lens on the Zorki also. As I said earlier, I don't have the skills to open up the lens. Used to be pretty good at motorbikes, specially old British ones, but that's hardly a help here.

 

[Sonnar Brian]

You have to move the optics out with respect to the RF cam. Moving the lens and cam out the same distance as you have done will get the distance scale to co-inside with the RF of the camera. As I read your original post, it was the actual focus and RF that disagreed. To correct that, you must move the optics module with respect to the cam. If the actual focus was closer than what the RF indicates, the shim must be reduced.

The Zorki and Leica use a different focal length for their RF calibration. You will not be able to go back and forth between cameras with this lens.

 

[payasam]

Thanks, Brian. I have had no trouble using an I-61 L/D and a Culminar 85 on the Zorki and the M2 (and earlier on a IIIc). My J-12 shows a slight error of focus at infinity on both the Zorki and the M2 -- but its focal length and maximum aperture mean that there is little wrong with the pictures. The J-3 shows the same divergence between R/F images on both cameras at infinity.

The photo attached was taken at f/1.5 by deliberately mis-focussing.

 

[Kim Coxon]

I think it is sometimes more a question of degree. In the same way that there are variations between some FSU lenses depending on their history etc, there are also variations between FSU bodies. The FSU bodies are adjustable so there is no reason I can see that an FSU body cannot be set to the proper Leica standard and then you could freely interchange the lenses.

It is also a matter of degree. If a lens is set to be "perfect" on a non FSU lens, then it may be not so "perfect on an FSU one. However, the difference may be so small that the difference is hardly noticeable without either "pixel peeping" or being ultra critical. In your case, I suspect that someone has done a re-lube or similar and either left out a shim when they re-assembled the lens or put the helix unit back together incorrectly.

If you set the lens to infinity and the RF patch does not line up on a distant object, the more likely reason is that the RF cam is wrong. This would be supported by the fact that it does if you need a paper shim between the lens and M mount adapter as this will shift the cam as well as the optic unit. Once you get this right, then you can check the focus of the optical unit. If this is still out throughout the range, then you need to look at the lens shims as Brian suggests.

Kim

Brian, I put a couple of bits of thickish paper between the J-3 and its M adapter. When mounted on the M2, the R/F images align at infinity. Will do a couple of test exposures in the morning. In the day, before the paper trick, I shot a few near range frames which were deliberately mis-focussed. The paper thing is hardly a solution even if it works -- after all, I shall need to use the lens on the Zorki also. As I said earlier, I don't have the skills to open up the lens. Used to be pretty good at motorbikes, specially old British ones, but that's hardly a help here.

 

[payasam]

Thanks, Kim. Beyond my abilities, as I said earlier. Beyond my comprehension too, at first reading.

To others following this thread: Kim just offered, in a private message, to fix the lens for me if I dealt with return postage.

 

[payasam]

Think I'll fool about a bit more with the paper shim approach. Always carry a knife with scissors, and a piece of suitable paper won't add much weight.