This lens an exact copy of Carl Zeiss Sonnar 50mm f/2 pre-war lens. So I expected pretty much from this test, I could test only in close-up action because Leica lenses on Nikon D50 doesn't work on longer distance. I found this lens is very sharp and it has good color rendering. Recommend for close-up works even on DSLR bodies, I guess very good performer on it's original place on many Russian Leica clones like Zorki cameras.
The Jupiter is a sharp lens which delivers excellent value for money. It does however suffer from contrast and flare problems. I suspect that the suppression of internal reflections is poor. For applications where the flare / contrast issue is not a problem the the Jupiter will deliver sharp pleasant images at a bargain basement price.
The lens on the Jupiter appears to be very clean with a nice coating. It's a Zeiss Sonnar clone, so I have high hopes about its performance, assuming that the Soviet manufacturing tolerances weren't horrendous on that day in 1957. I have to say that I'm very happy with the Jupiter. The contrast and color rendition is quite good. The focus seems accurate. There's really nothing to complain about it (except that the aperture ring doesn't have click-stops).
The edges may not always be the bee's knees, but the center can be dead sharp with killing contrast. Is also said to be a good color optic.