--- You wrote:
How much difference in frame length could that make?
Art
--- end of quoted material ---
I expect quite a lot when you are looking at figures like 99.5 %. Fractions of
a percent! It would be easy to do the geometry to see how the gap would affect
accuracy at different focal lengths.
It would have been simpler before lenses got so complex too. Years ago, lenses
weren't so far from the pinhole, where all the light came from one point. I
don't know the terminology, but in modern lenses, retrofocus and so forth, a
lens set at 50 mm might send light to the film plane as though the center of
the lens were 90mm away or something similar.
It's pretty remarkeable that thye get the registration as true as it is.
Rich
