My 35/2 with the concave front element is the 35/2 FD SSC. I gave it a light treatment which must have gone on for eight months. This was done with a CFL lamp amd aluminum foil on the bottom. If I had a UV lamp it would have been faster. The color is almost completely clear. If I had to shoot something on color slide film where the exact color was critical I might switch to a 35/2 New FD. The FD SSC is extremely sharp. I have had lenses completely overhauled too. If you enjoy using the lens it's worthwhile.