I've got a question for those of you who are knowledgeable about lens-to-camera interface theory. One of the advantages of rangefinder camera design is said to be eliminating the mirror box of SLR cameras and the resulting compromises in o ptical performance, especially with wide-angle lenses. To quote from the Mamiya 7 brochure: "A significant advantage of rangefinder camera design for the opti cal engineer is the elimination of the mirror box and the resulting shorter flan ge focal distance which permits placing the rear lens element close to the film plane. Various other restraints on lens design are also removed, providing far more versatility in coming up with a lens composition that approaches ideal opti cal theory." I own a Mamiya 7, and it's certainly true that with lenses like th e 43mm and 65mm, the rear element seems to be backed right up almost against the film plane (in fact these two lenses protrude so far into the camera body that the instruction manual warns you, when mounting either of them, to take care tha t the rear lens rims do not touch the rangefinder coupling roller). Martin Sil vermann, a Mamiya rep responding to a question at the Mamiya website (and before you discount his words as those of a salesman, remember that he's selling both rangefinder and SLR systems), noted: "The real virtue of any rangefinder system over an SLR system is in the inherent design advantages of RF wide-angle lenses . Since there is no mirror box to contend with, RF wide-angle lenses can be "str aight" or "true" wide-angle designs, where the focal length is more in line with the actual film-to-optical-"center" distance (actually in most cases, the rear nodal point, for your optical buffs). SLR wide angles are "retrofocus" design, which leads to all sorts of compromises in order to allow focusing through the m irror system. In the end, the RF design will yield superior results, all other things being equal."

My question is, if all this is true (and I'm not suggesting that it isn't), how do large-format photographers get such sharp images, when the rear elements of t heir lenses may be at some considerable distance from the film plane? Doesn't there seem to be an anomaly here? Why doesn't this distance seriously compromis e optical performance?