Hello,
don't take an AF lens since they are not well suited for manual focussing because they have only a very small turning angle from infinity to 0.45 m. The series E and the latest AiS 1.8/50 without coupling has only a minimum distance of 0.6 m and has a simplified coating. The Ai 1.8/50 is a very good lens, but is quite rare on the market. The 2.8/45 pancake with CPU which was offered with the FM 3a has no good reputation.