Hi,
I've been having trouble finding information about filter ring diameter for industar 50. Finally, figured it out and thought I would share it (with illustrations).
Filter ring diameter is 33mm.
There are vintage filters of this size available on ebay for about $22-$25 + shipping from Eastern Europe or UK
I got a step-up ring 33 to 37mm ($4), UV filter 37mm dia. ($5) and lens hood 37mm with cap ($5), all new, made by Sonia (India)
The
result, mounted on K7 with M39-M42 and M42-PK, looks like a distilling apparatus but it takes picture, focuses to infinity, etc.
Quick sample photo is
here. (not color corrected)
I have Zenit 3M which I used to take b&w pictures and I thought the lens was great. I look forward to testing it with dslr.
Hope this info will help somebody else.
M.