The OP was asking specifically about the Jupiter 3's and in my limited experience with these lenses (I have had 5-6 in LTM) I haven't seen any good rules of thumb. The one I still have is a black one from the 70's, it is pretty sharp, and most of the others were silver from the 50's and 60's, and they varied from pretty good to pretty bad, but they probably could be adjusted to work fine. These lenses were made in different factories and that adds another set of variables to the QC factor. Lore says the the contax/kiev mount lenses have better build quality than the LTM, which makes sense as the the Kiev was the higher end camera. I love my lens and I only wish that this design was available for an SLR. Great for portraits with a nice, smooth out of focus background.