May I also just mention that the 40mm f4 Zenzanon-S has a filter thread diameter of 95mm, and has a built-in lens hood, not sure if and what filter you would use like screw-in or Cokin/Lee holder types, screw in filters in that size WILL cost you a pretty penny, and I have no idea whether there is a work around for the holder types (maybe some other members could say?) just bare this in mind. I think the later PS version does not have the lenshood.

The 50mm has a 67mm filter thread, as do all the other lenses (except for the 40mm, 500mm, and the two zoom lenses)