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-   -   Jupiter 8 on m42? (http://www.rangefinderforum.com/forums/showthread.php?t=167180)

Barry Kirsten 12-24-2018 15:01

Jupiter 8 on m42?
 
I'm impressed by the images on the Jupiter 8 thread and as I love the rendition of Sonnar lenses began to think of getting one. However when looking at samples on the auction site it became apparent that apart from a few which are modified e.g. for Nikon, they're all ltm m39 thread.


This raises the question of compatibility for m42. The flange-film plane distances for the two standards are different - 45.2mm for m39, and 45.46 for m42. Granted the difference is small - 0.26mm - but I would have thought this is significant, especially at large apertures and close subject distances. What do people think? And are any of you using J8s on m42? Appreciate any comments.

santino 12-24-2018 15:24

The only sonnar type 50mm for slrs I know of is a quite rare pentax lens.
You won't be able to use your J8 on M42 cameras (but M42 lenses on ltm cameras).

The cheapest sonnar type you could get for m42 is the j9 but its 85mm.

Ko.Fe. 12-24-2018 19:12

Everyone who wants it FSU special goes with Helios 50mm lenses on SLR.
Glass and Metal.
I had Helios 81H. It made Cron 50 looks like overpriced boo-boo.

Barry Kirsten 12-24-2018 20:41

I part answered my own question whilst dozing in my chair after Christmas lunch. These J8s seem to come with 39-42 adapter, so they can fit in an m42 body. And of course, in a reflex camera as long as the image is in focus on the screen, it should focus on the film, or else how could extension tubes work? I hadn't thought it through properly.


So I'm wondering now if anyone with m42 has successfully used a J8? But I'm now also looking at Helios, although these are not Sonnar. Thanks for your input.

santino 12-24-2018 22:32

The adapter is for m39 zenit slr lenses. With such an adapter you can mount them on m42 slrs. Its basically a step up ring.

Rf lenses like the j8 won't focus correctly on slrs because of the flange distance (the lens has to be close to the film, in slrs there is the rather large mirror box in the way).

retinax 12-25-2018 00:27

Perhaps you're confused with the J9, that is available in m39 for Zenith SLRs, as well as in l39. The J8 can not work on any SLR (except for close-ups), the optics sit too close to the focal plane, in the position occupied by the mirror in an SLR.

Phil_F_NM 12-25-2018 10:09

The only true sonnars for SLRs you can use will be over 90mm due to the physical constraints of the formula. The original 10.5cm Nikkor for the Nikon F was about the shortest you could find this formula. No such thing as a 50mm Sonnar for an SLR that reaches infinity focus.
Phil Forrest

Barry Kirsten 12-25-2018 10:14

Ah, so I was right after all. They'll focus for distances less than infinity, but not all subject distances. I had an idea that flange-focal distance was important. Thanks.


As santino mentioned, there are a couple of old Pentax Sonnars, the Takumar 58mm f/2 and 58 f2.4 which I have on my list of interesting lenses.

Sumarongi 12-25-2018 10:20

Quote:

Originally Posted by Barry Kirsten (Post 2857201)
This raises the question of compatibility for m42. The flange-film plane distances for the two standards are different - 45.2mm for m39, and 45.46 for m42. Granted the difference is small - 0.26mm - but I would have thought this is significant, especially at large apertures and close subject distances. What do people think? And are any of you using J8s on m42? Appreciate any comments.

«45.2mm for m39» —— well, that's *not* rangefinder-M39*26tpi, but «Early Russian SLRs (Zenit) (not to be confused with M39×26tpi and M39×1/28,8)».

See here: https://en.wikipedia.org/wiki/Flange_focal_distance

As others mentioned, you probably won't find a 35mm-SLR-Sonnar < 85mm focal length anywhere...

David Hughes 01-13-2019 01:36

As soon as I read M42 I thought of SLR's and then realised that there are no Jupiter 8's available for them.

The problem is that there is not much clearance behind a J-8 for the mirror box. From the film plane to the glass at the back of the lens is 27.75mm (at the infinity focus); or the aperture blades are 42.14mm from the film plane to give a better idea.

So the obvious answer, for me, is buy a cheap USSR made film rangefinder or a dear Leica digital, or something in between. And, of course, there's the Contax/Kiev route to explore but I can't think of anything else; although there may be something in the CZ range. Anyway, I'll wish you luck.

Regards, David


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