I read the instructions on how to locate the entrance pupil but I would like to use an NN3 with a film rangefinder camera. That means the viewfinder is not looking through the lens and will see parallax when camera is rotated.
So my question is: How do I work out where the entrance pupil is on a film rangefinder camera? Is there a special technique for this kind of camera. I will probably be using 35, 50 or 85 mm lenses.