[Leica] Retrofocus: question for Erwin Puts?

[Gaifana@aol.com]

One of the places that rangefinders excel is with wide angle lenses. It is my 
understanding that this comes from the fact that retrofocus designs are not 
necessary with lenses under 40mm, as they are with SLRs, since the lenses do 
not have to focus to clear an SLR mirror. (Of course, with TTL metering, you 
now need "some" retrofocus to not block the sensor).

I also noticed  that the older Contax lenses, like the legendary 21mm and 
35mm Biogons have significant rear-extending elements, which bring the rear 
glass even closer to the film plane. It is my understanding that Leica did 
not bring out a competitive lens until the 35 summicron (which explains why 
the M3 didn't need a 35mm finder and instead took on Summaron with eyes).

(1) How much of an effect does lack of retrofocus have on the performance of 
a lens? 

(2) How about distance to the film plane? I think this should increase 
transmission.

(3) Or is the higher sharpness of rangefinder lenses attributable to smaller 
glass that is easier to produce?

Thanks
Dante