In almost all forums , I read that the Industar 61 LD 50mm lens has more contrast and is sharper than the Jupiter 8 50mm lens. I recently bought a very nice 1957 Jupiter 8 lens from RetroPhotoHouse , polished aluminium with external knurled focusing knob.Focusing and apertue operation as smooth as silk . At the same time I bought a new/old stock Industar 61 LD (1990) from another Ebay seller.Lens is just as smooth and in great condition.These were to use on my 1957 Zorki4 when it arrives from Oleg at OKVintageCamera.As Oleg says "Any soviet camera or lens ó small lottery. As other soviet production they may have unstable quality. You may get excellent thing or absolutely unusable item. So, if you have a good Jupiter lens ó you win that lottery. For any LTM camera I can recommend Industar-61 lens. Itís a cheap, but may get nice picture (if you win the lottery!)" As the Zorki hasnt arrived yet I did some very controlled testing with both lens on my 36mp Sony A7r and the results were surprising.The Jupiter 8 was not only sharper but had better contrast than the Industar 61 LD.Perhaps its like Oleg said - I won the lottery with the J8 but losy it with the Industar 61 LD.For around 25euro is it worth trying again with the Industar with another lottery ? Appreciate any thoughts.
The year before last I had a fed 2 (d4) and an indistar 61LD and a jupiter 8 (which had a bunch of scratches in a small area that was a bit like the etching done by fungus), and I used both lenses on one film and I noticed that there was a very similar difference in colour "cast". If both lenses were identical in performance then I'd still chose the J8 as it offers a slightly wider range of apertures which partially compensates for the narrower shutter speed range of a fed compared to a zorki. The rangefinder patch was very pale though, and with it being smaller than a zorki's it was harder to use.
I do see that the writing on the inside of the label seems to be more visible with the 61LD than it is with the J8. Perhaps the radioactive Lanthanum has got X-Ray properties, lol.
There is not much that can really go wrong when grinding, polishing and coating optical glass. It's a process that takes a certain amount of time and patience.
However, the assembly and optical centering of the lens is vital for it's performance. The result is the sum of the errors. That's the lottery part. The beautiful Gauss curve. The Soviets simplified and reduced a lot of the assembly steps in comparison to (for example) Zeiss Jena to speed up numbers.
If the optics are good, cleaning, reassembling, recentering, shimming and collimating a lens can improve performance significantly. It takes a lot of efford, and you need the right equipment.