David J. Valvo:
"Range finder camera lens designers don't have that problem."
Not exactly. For the standard 24mmx36mm 35mm film frame, lenses 50mm and longer do not have any penalty when designed for SLRs or rangefinders; this is because the optically best design puts the lens element closest to the film plane relatively far away, leaving plenty of room for the mirror. Shorter than 50mm, however, is wide-angle territory, and the optically best position of the rearmost lens element moves closer to the film plane the shorter the focal length becomes. With rangefinder cameras, this is not a problem, but with SLRs, other than with the now sadly limited "mirror-up" lens designs, a compromise is required. Wide-angle SLR lenses are generally designated as "retrofocus," that is to say, inverted telephotos. This design puts the rear lens element further from the film plane, but does not perform as well as a "true" wide-angle design. For an excellent ex&le of this, including world-class Zeiss technical documentation, check Hasselblad's web site and compare the performance of either of the 40mm Distagon lenses (one is brand-new) available for Hassy SLRs versus the stellar performance of the Biogon 38mm lens, found on the 905 SWC (Super Wide Camera). The Biogon 38mm is an optically "true" design and has been hailed as perhaps the best wide-angle lens ever designed and manufactured. Rest assured that the Distagons are among the finest ex&les of retrofocus lens design, but not even Zeiss can escape the inherent sacrafice which must be made in SLR wide-angle lens design.