I was keen to try an old lens from a Fujica on an EOS camera, but when I took off the Fujica M42 adapter to put the EOS one on I found that the threads were not the same pitch.
Thread pitch for EOS-M42 is 32 threads/inch, and for the Fujica-M42 it is 25 threads/inch. They are both of the same diameter (42mm, I guess).
It only went on about a thread or two, so I wasn't going to force it on.
Anybody know about this fact? I have searched on-line but have not found anything on this.