I have a SMCP-A 50/1.7 with a very small chip near the centre of the rear element. It normally has no effect, but sometimes 'lights up' when the sun is in-picture and produces a pattern of reflected hot spots (not flare, but certainly related). I plan to do a resolution test of this lens and two other SMCP-A 50/1.7, before and after the 'black marker' fix on the damaged one.
Jim www.jcolwell.ca
