On Sat, 14 Jan 2017, Chuck Guzis wrote:
Looks to be 38mm indeed. Rather than burn $40 on a
protective filter,
I'll probably just buy one of the Chinese coated "peel and stick"
filters for $2. Shouldn't hurt until the real thing wanders my way for
cheap...
Photographic filters most often have a 0.75mm thread pitch, in MANY
diameters.
38mm is not very common, but "step-up" adapters from 38mm to 52mm, or 38mm
to Series VI are available.
With a step-up adapter, would a polarizing filter be useful?
some other common photographic threads include:
0.8" x 36tpi whitworth RMS microscope lenses
25mm x 0.5mm Schneider some enlarger lenses and Compur 00
39mm x 26tpi Whitworth Real Leica
39mm x 1.0mm Fed, Japanese imitation Leica stuff, most enlarger lenses
39mm x 24tpi some early Canon
42mm x 1.0mm Pentax
42mm x 0.75mm T-Mount
1/4-20 UNC Tripod
3/8-16 UNC older/larger tripod (not counting the Royal Photography
Society recommended 3/16-24 BSW, 1/4-20 BSW, and 3/8-16 BSW (UNC is 60
degree threads, BSW is 55 degree)