Little Prince
Well-known
I can confirm that the 'standard' 39mm thread (which is the same as the E39 thread) is different from the CL 39mm (C-Summicron) thread. The former is 39mmx0.5mm pitch and the latter is 39mmx0.75mm pitch. All regular 39mm filters produced today by prominent manufacturers (B+W, Heliopan, Hoya, etc.) seem to be 0.5mm pitch. I have this from contacting the manufacturers themselves. I have even tried a regular 39mm Hoya filter on the C-Summicron. It cross-threads of course, but goes in quite well. Maybe 1 rotation or so short but I found it quite securely in place without forcing it. But then that is quite difficult to measure, it is possible I had actually forced it a little without thinking I did.