Hamster
Established
I was just wondering if any J8m were ever made in m39 mount. I have yet to see one.
If such a thing do not exist, is is possible to transplant a Kiev J8m optical block onto a m39 J8 helical mount? I would have thought given the equidistance aperture control and click stops it would the logical thing to do.
If such a thing do not exist, is is possible to transplant a Kiev J8m optical block onto a m39 J8 helical mount? I would have thought given the equidistance aperture control and click stops it would the logical thing to do.
Spyderman
Well-known
No, there were no J8M in LTM. Only adapted.
It is possibleto transplant the optical block, but the aperture is often very stiff. You need to use one of the focussing blocks where the filter rim doesn't move during focusing. The latest variant where the filter rim moves would be difficult to use, because you would have to hold the lens body and only then change aperture. Even worse than the original method without click stops.
Kiev is more tolerant to the stiff aperture ring, because of the infinity lock, and also you can hold the focussing wheel and then turn aperture ring.
Anyway you can try the surgery... theoretically it should be compatible.
It is possibleto transplant the optical block, but the aperture is often very stiff. You need to use one of the focussing blocks where the filter rim doesn't move during focusing. The latest variant where the filter rim moves would be difficult to use, because you would have to hold the lens body and only then change aperture. Even worse than the original method without click stops.
Kiev is more tolerant to the stiff aperture ring, because of the infinity lock, and also you can hold the focussing wheel and then turn aperture ring.
Anyway you can try the surgery... theoretically it should be compatible.
santino
FSU gear head
yeah, I saw the Industar 61LD in kiev mount in the kiev survival site 
Nickfed
Well-known
Hamster said:
I think the the first thing to do is to investigate the significance of the "m" in Jupiter 8m.
Hamster
Established
Nickfed said:
As far as I can see the difference between J8 and J8m were click stops and the stops distance were linear as opposed to logarithmic, additionally the rear cemented doublet were made smaller on the J8m, not so sure if they actually changed the prescription. Perhaps the front element and the triple cemented group were interchangeable between J8 and J8m, however I never tried. Hopefully experts such as Kim can shed light on that, he had an excellent repair guide for m39 J8s on his website, all 4 version of the lens were covered.
Xmas
Veteran
Observation seems to indicate that the blackening (of both Kiev and LTM J8) is better than for J8m. None of the J8s had 'diamond necklace' rings on the rear element, some of the J8m are pretty bad.
This wont help contrast at f2, but has reduced impact if stopped down, dont throw your J8m away.
One would need someone with a large sample of lenses to confirm.
I thought the triplet group was the rear group and the middle was a doublet any one know for sure?
Noel
This wont help contrast at f2, but has reduced impact if stopped down, dont throw your J8m away.
One would need someone with a large sample of lenses to confirm.
I thought the triplet group was the rear group and the middle was a doublet any one know for sure?
Noel
Hamster
Established
Quite sure middle group is a triplet and rear group is a doublet. This site also confirms:
http://www.baierfoto.de/russobj/objektive.html
http://www.baierfoto.de/russobj/objektive.html