FED 2, J-12 query

[JonP]

Just playing with my new J-12. Tried it on my Fed 2 type b and all is fine at infinity well 15m, I can measure that accurately. It is also fine further away. At 1m according to the lens, actual and r/f give me 3m (I have tried a known J-8 from the same position (on the FED ) and my other 4 J-8s are fine as is a J-11, I-61, I-22, I-50 and Orion 15 all appear to rgister true on the FED.
The J-12 also appears fine on other cameras including an Oleged Zorki 3M.

Oh, with a ground glass the r/f and actual distance are fine down to 3m, and that's where the lens stops

Any ideas what is causing the problem?
Or a solution, other than buying another FED 2 especially for the J-12 and of course another J-12 for other cameras
Thanks
JonP

 

[Spyderman]

No idea.

Please try to describe your "test-cases" more accurately. (i.e. each test case separately).

 

[JonP]

Ok I thought I'd try the J-12 on my FED 2 before using it in anger. It's raining so no going outside.
Tried the J-12 on the Zorki 1 it came with. Focused on street light at 15m away, I know this I've checked it before, everything correct, distance is 15m, lens says 15m and r/f aligned. Tried the window frame at 1m, same results. Tried same with J-12 on FED 2, 15m test fine, 1m test, lens moves to 1m, I had to move away to 3m for the r/f to align. Still at 3m swopped lens for J-8 that I know is correct, 3m came out as 3m away, lens read 3m and r/f aligned. Tried combination of most lenses with most bodies at 1 and 15m, only the j-12 on the FED 2 gives this error.
I know its not highly and there are no pictures to prove it, but I did check by mounting the camera on a tripod and checking with a ground glass and 10x loupe.
So at 3m with the FED2 and J-12 set at 1m and r/f aligned focus is as far as I can tell spot on.

 

[fidget]

Just a thought, I had problems mounting a J12 on my FED2. I had to bend (or move) the rf cam following arm up to clear the lens glass properly. I then had a small problem like yours where the arm would not follow the lens cam outwards as it started to bind on the glass, but only very lightly, not leaving a mark. I needed to raise the arm a little more to ensure that it cleared the glass of the J12. I guess that only the J12 presents such a lump projecting from the back of the lens.
I believe that J12s frequently give this problem on FED2's.

Dave...

 

[Spyderman]

Maybe the FED 2 needs calibration of close focusing... The drop shaped thing on the RF arm.

Do other lenses focus correctly with the FED 2 ? At infinity as well as close up?
If YES, then it's probably what fidget wrote.

 

[JonP]

The other lenses are all fine. It seems a shame to attack the FED2 just for one lens. Is it true that some J-12s have a smaller rear element? If not I may have to use another body, or buy a dedicated FED 2 for the J-12.

 

[fidget]

The other lenses are all fine. It seems a shame to attack the FED2 just for one lens. Is it true that some J-12s have a smaller rear element? If not I may have to use another body, or buy a dedicated FED 2 for the J-12.

The idea is that the camera remains usable for all lenses. The amount that the arm is bent up is probably only 1/2 to 1 mm. Maybe another FED2 is a good idea, then 3a etc....etc...

 

[JonP]

3a arrived last week, hmm another FED 2 !! Did I really need an excuse?