Quote Originally Posted by Dan Fromm View Post
QG, when a lens is focused at infinity its rear nodal plane is one focal length from the film plane. The exit pupil can be anywhere, as long as its in front of the film plane. This is one definition of focal length.
Agree.

The bit that concerns the light loss question is that about where the exit pupil is.

Quote Originally Posted by Dan Fromm View Post
Do you agree that the relationship between magnification, focal length, and extension, defined as the distance between the lens' rear nodal plane and the film plane, is e = f * (m +1)?
Yes.

Quote Originally Posted by Dan Fromm View Post
There is a convention, and I think you follow it. PM = exit/entrance.
Good to hear that!