Perfect lens designs are symmetrical, and their sizes and distance from the film/sensor are related to the focal length. Since normal cameras do not have flange distances, you can only make perfect lenses down to a certain point, and if you want a smaller focal length (wider lens), then you can\'t move the lens close enough to the sensor to get a perfect symmetrical design, and so you need to design a lens with retro focal design, which trades off some characteristics for a wider angle of view at a larger flage distance.
The Leica M lenses have a shorter flange distance, and they can have more perfect wide angle lenses than the R. This is also why the Hasselblad SWC with its Biogon is a more perfect wide angle than the Hasselblad V 40mm Distagon, even the latest. In fact, in Zeiss speak, I believe that Distagon means retro focal and Biogon means (nearly) symmetrical, for their wide angle lenses.
Aug 04, 2012 at 04:54 AM
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