Was Leica the first to use a "normal" lens in 5cm for the 135 format? Any particular reason why this focal length was chosen instead of other nice round numbers like 40 or 45mm, both being closer to the format's diagonal length? Other focal lengths like 135, 35 and 28mm also became "standard offerings" across brands (e.g. Zeiss) right from the beginning, AFAIK. Why is that? No such "agreement" among makers WRT to short teles - we had 85, 90, 100 and 105mm.