J-9 LTM to M42 swap?

[Sam N]

Not sure if this is the right place to ask this, but...

I have a J-9 that doesn't focus properly on my RFs. It's useable at smaller apertures and further away, but the problem is more than a shim will be able to fix. The glass and aperture are in great shape.

The optical part of the LTM J-9 screws off... will this screw into the mount of an M42 J-9 for SLR use? I was thinking of getting one with bad/broken glass and just making a frankenstein lens.

 

[feenej]

M42 is a lot bigger than ltm, M39 I think. You would need an adapter.

 

[Sonnar Brian]

Most FSU lenses interchange optics modules, but I have not done that conversion first hand.

Kim Coxon has instructions for the J-9 on his site. If the focal length is too long, you can adjust the spacing between the front and rear group.

 

[raid]

So, if I have a nice J-9 in Contax mount and I get a J-9 LTM with bad optics, I could just switch the optics to get an LTM J-9 with good optics?

 

[Sonnar Brian]

Yes, but you have to shim it properly in the new mount.

 

[Murray Kelly]

This prompts me to ask why a J-3 optical unit I bought won't screw into either the LTM or CK J-3 lenses I also have. Looks right but the threads are a tiny bit different. I have a couple of I-61 lenses - maybe I should try it in one of those?!

Murray

 

[Sonnar Brian]

The design of the J-3 focus mount changed ~1951. The threads never changed, as i've put a 1935 CZJ SOnnar into a 1970's J-3 mount. BUT- the length and tapering around the F-Stop ring did change. The J-3 optics module changed design ~1962. Note if the rear module is in a fixture that unscrews from the unit as a whole- the earlier design. Later design, the optics fixture is one piece and the rear glass is held in with a retaining ring.

 

[Murray Kelly]

Ah-ha! The optic unit is '84. The others are '56 and '64. You'd have to change the mount to get the thing to thread in perhaps? It felt just like that. Doesn't matter. I bought it on spec. I'd be more interested in getting a Helios-103 into a LTM mount.
Just saw another thread you were contributing to about the J-3. Sorry to get OT here.

Luckilly my J-9 s are OK but for some looseness in the helical. I figure the tiny off axis wobble isn't important to me. The LTM sample has amazing resolution.
I wonder if Sam N's problem might be an element put in backwards? Must be a diagram somewhere of the optical internals. Showing the elements and groups so he could just check it's not just something as 'simple' as that?

The M42 register is way different. I could see problemos there.

Cheers and thanks
Murray Brisbane

The design of the J-3 focus mount changed ~1951. The threads never changed, as i've put a 1935 CZJ SOnnar into a 1970's J-3 mount. BUT- the length and tapering around the F-Stop ring did change. The J-3 optics module changed design ~1962. Note if the rear module is in a fixture that unscrews from the unit as a whole- the earlier design. Later design, the optics fixture is one piece and the rear glass is held in with a retaining ring.

 

[Sonnar Brian]

The 84 module should go into the 64 J-3 mount.

Getting a Helios-103 into an LTM mount is hard.

 

[Sam N]

So nobody has an LTM J-9 and an M42 J-9 lying around? It would be pretty easy to test this.

 

[Sonnar Brian]

I've put a 1941 8.5cm F2 Zeiss module into a J-9 before, and a J-11 swap from SLR to Contax mount. I do not have an M42 J-9.

Just be careful of the shims... Had a hard time getting the thin aluminum foil shims back on the J-9 after testing with the Zeiss.