Quote Originally Posted by SMBooth View Post
if the film to hole distance is about 55mm then a pinhole diameter of .3mm is fine, your .34 will work fine to just adjust the f stop. That's f183 for the .3mm and f161 for your .34mm

The film plane to inner flange distance would be 55mm, yes. But a body cap adds about 8mm (the Pentax one I have), placing the pinhole further away? I noticed this when I put the body cap on the 67 earlier. Just a thought. I have been mulling a pinhole for the 67 for a few weeks now. Most interesting.