Quote Originally Posted by bjorke
For RF lenses, more of the light that strikes the lens ends up in the correct place on the film. There is less diffusion. The OVERALL amount of light at f/2.8 is theoretically the same. But correct placement contributes to better sharpness and higher contrast, hence the high regard for RF glass.
Uh ... I don't want to start anything, but ... Do you mean to suggest that the light from an "ordinary" (non-retrofocus) lens DOESN'T "end up in the correct place on the film"?
When you speak of "diffusion", do you mean "dispersion"? - With more glass, there should be more, not less...