Originally Posted by
Ole Tjugen
Here's what Michael wrote, and it's absolutely correct. It's the entrance pupil which must be measured, as the "magnification" of the front cell affects the light-gathering ability.
If you object to that, take a close look at a telephoto lens - something like an old Tele-Xenar 360/5.6. The entrance pupil of that lens is 64.3mm, yet it's in a Compound #3 with a 55.69mm cell thread. That's almost 8.6mm too small! And the max physical aperture opening is even smaller than that. Clearly the glass of the front cell makes a difference.
Bookmarks