Fed 3a & Jupiter 12

[lawrence]

Is there a compatibility problem between the Fed 3a and the Jupiter 12? I can mount the J12 on the 3a if I remove the rear elements (they just screw out) but not with them in. The J12 is an old silver one.

Thanks

Lawrence

 

[Roman]

Try setting the lens to its closest focussing distance befor mounting, this sometimes makes it easier...
Or maybe the coupling arm in your FED is bent a bit?

Roman

 

[lawrence]

Thanks for the advice. I tried that but it still doesn't want to screw in -- will only screw in if rear element group is removed. There definitely seems to be a problem...

Lawrence

 

[sockeyed]

I agree, there must be a problem, most likely with the body. My 1958 J-12 mounts on my Fed 3a easily, no matter how the focus is set.

I have had problems mounting my j-12 on my Fed-2, but that's because I think that rangefinder cam is a bit bent.

 

[lawrence]

Fec 3a & J12

Fec 3a & J12

Thanks -- I think I have tried everything now. I don't think it's the camera -- it seems almost unused and all other lenses screw in fine -- but it is weird as my J12 is also from 1958. The rangefinder cam looks fine to me so I guess it's just a bit of a mystery...

Lawrence

 

[pshinkaw]

Try taking off the back elements of the J12 and mount it on the Fed-3a. Then set the shutter to "B" and trip it with the back removed. You should be able to look in the back and see where the rangefinder cam sits on the coupling ring. Some Feds have their cam arms set a little low. As a result the cam will ride on the coupling ring, but will intrude into the space reserved for the lens elements. Since there is so little extra clearance for the J12, The cam could be bumping the back lens element.

Ideally the can should ride on the center of the coupling ring, but I have seen Feds where the top edge of the cam just barely touches the bottom of the coupling ring.

-Paul

 

[FrankS]

The first time I mounted my J12 lens onto my FED 2e body, I had to bend the cameras RF cam arm upwards about 1mm, then it fit.

 

[kiev4a]

The first time I mounted my J12 lens onto my FED 2e body, I had to bend the cameras RF cam arm upwards about 1mm, then it fit.

I would bet on the focus cam, too. The J-12 seems a little more sensitive to a misaligned cam than some other lenses. Just apply a little pressure upward on the cam. It probably won't take much to allow the lens to clear. It's also a good habit on all the LTM lenses to make sure they are focused so the focus ring is as far backk into the lens as possible when mounting.

 

[lawrence]

Many thanks to all for the excellent advise -- it was the cam and now I've bent it up a bit the lens fits perfectly. This forum is just the best!

Lawrence