Why isn there a Leica “Digital M”?
Because! OK, that’s not good enough. There are no Leica M style digital rangefinders because it’s very hard to make one. One big advantage of a rangefinder (for normal and wide-angel lenses) is that it uses symmetrical lens designs. These are simple and compact, yet achieve very high quality. They have the disadvantage of causing the light to strike the film at angles far from perpendicular. Light from the 12mm Voiglander Heliar (a rather extreme example) actually reaches an angle of 60 degrees from perpendicular in the corners of the image. For such lenses, the “exit pupil” (the point in space from which light seems to originate) is very near the “optical center” of the lens. Film is very tolerant of such wild angles of incidence. Modern digital sensors are not so tolerant. Many show very objectionable vignetting if light deviates from perpendicular by just 10-15 degrees. Few are usable past 20 degrees. That means that no “rangefinder style” normal or wide angle will work well. So, ju
