Nice review, but I disagree about filters. The Canon 48mm are nice but lack modern coating. I would opt for a 48 to 49 or 48 to 52 step ip ring and modern multicoated B+W or Hoya 49 or 52 filters. With a 40-49 or 40-52 stepup ring could use same filters with that 25/3.5. 40mm filters are a pain to find and are needed on many other Canon ltm lenses (28/2.8, 35/2, 35/2.8, 50/1.8 etc).
Nice review, but I disagree about filters. The Canon 48mm are nice but lack modern coating. I would opt for a 48 to 49 or 48 to 52 step ip ring and modern multicoated B+W or Hoya 49 or 52 filters. With a 40-49 or 40-52 stepup ring could use same filters with that 25/3.5. 40mm filters are a pain to find and are needed on many other Canon ltm lenses (28/2.8, 35/2, 35/2.8, 50/1.8 etc).
Yeah for "standard" pictures, coatin filters are better, for infrared sometimes not.
By the way, i normally use B+W or Hoya filters for infrared.