I am trying to design a custom-built focusing helicoid and wonder what the pitch should be. My Contax Zeiss lenses extend ca 12 mm per full turn (calculated; they don't turn 360°), whereas my newly acquired 125 mm Macro (!) Apo Lanthar extends about 35 mm per turn, which I find all too much for my use.
The pitch of the Zeiss lenses is suitable for me. The strange thing is that the 35 mm Distagon and the 85 mm Sonnar have the same pitch. So could I just use the same pitch for a universal focusing helicoid for all focal lenghts? Or should the pitch be finer for longer lenses, because of lesser DOF? Unfortunately I have no Zeiss lenses longer than the 85 Sonnar to compare.
The immediate use would be for the 125 and 180 mm Apo Lanthars. But I can already see the next candidate for this adapter: the Contax 60 mm Macro Planar C...
Thank you for your info! - Hening
