In the past, wide aperture lenses ( f / 2, f / 2.8 ) were very expensive, due to their complex mathematical design and manufacturing know-how required, at a time when all computations and glass making were done by hand.
22.
For instance, the removable back was for faster loading and reloading, the bayonet lens mount was designed for rapid lens interchangeability, the long-base rangefinder was for more accurate focusing with large aperture lenses, and the vertical metal shutter not only gave a faster maximum speed but also banished the problem of shutter blinds burning.
23.
Very-large-aperture lenses designed to be useful in very low light conditions with apertures ranging from f / 1.2 to f / 0.9 are generally restricted to lenses of standard focal length because of the size and weight problems that would be encountered in telephoto lenses and the difficulty of building a very wide aperture wide angle lens with the refractive materials currently available.
