I was allowing for the lens cap. My measurement wasn't exact as I couldn't get the mirror up as I have a roll of film in it. I never have figured out how to fire the shutter without film in the camera even though I've owned it for 20 years, just never needed to!

Quote Originally Posted by Poisson Du Jour View Post
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.