Quote Originally Posted by g0tr00t
Thanks for the responses. I am taking a photo class now and the teacher said that since the lens elements are closer to the film plane in a rangefinder than they are in an SLR, you get "more light" using a RF at 2.8 than you would using an SLR.
Confused me too and am still confused...
Confuses me too!!

I would say the instructor was asked a question, and not knowing the answer, tried to create something.

A wide angle lens on a single-lens reflex camera tends to be more complex ... requiring more elements (read: retrofocus). That usually means more air-to glass surfaces... and less efficiency. Very little less efficiency. DAMNED little less efficiency.
It may be of concern in certain photometric (read wild scientific) applications. but for anyone with a modicum of sanity, it means *nothing* in any type of photography in which the most fastidious photographers - as we know them - might be involved.