Choosing Rangefinder Lenses for Leica M Cameras
The term rangefinder lenses primarily refers to those lenses designed to fit Leica's range of cameras with the M-type camera mount. Several manufacturers make these lenses, and besides Leica, there are some manufacturers making film and digital cameras using that mount.
What Are Leica M-Mount Lenses?
Leica introduced M-mount 35mm lenses in 1954 when it launched its first M-type camera, the M3. This type of mount has a quick-release bayonet fitting for Leica's range of 35mm and digital rangefinder cameras. Unlike other camera manufacturers that now use electronics to control their camera lenses, Leica has stayed with an all-mechanical construction. This means Leica lenses still have manual aperture rings and manual focusing, a characteristic shared only by digital cinema lenses. Virtually any M-mount lens will fit an M-mount camera, so it's possible to purchase new lenses for any old Leica cameras and vice versa.
Characteristics of M-Mount Lenses
Thanks to compact camera dimensions, the distance between the lens mount and the sensor is short. This means that rangefinder lenses are small and light, yet offer excellent optical qualities. Leica rangefinder cameras use a prism arrangement in the viewfinder to identify the correct focus point. A cam fitted to the lens activates this prism.
Leica's rangefinder lenses are made of metal and use high-quality glass, producing good results. While not as expensive, lenses from Zeiss and Voigtlander also work well. Several other manufacturers also supply compatible lenses as well as some special effects lenses for M-mounts.
Camera Compensation for Different Focal Lengths
Rangefinder cameras have separate optical viewfinders with fixed magnification. When attaching a lens with a different focal length, its field of view changes. The camera compensates for this so that it correctly frames photographs in one of three ways. First, digital rangefinder cameras have a series of LED lens frames that illuminate in the viewfinder when activated by a six-bit barcode on the lens. Alternatively, lens information may be manually entered. Because lens frames don't cover all possible focal-length combinations, separate optical and digital viewfinders matching specific focal lengths are available for attachment to the camera's hot shoe. Finally, if the camera has a live view screen, you can use the screen for focusing and composition.
Fitting Rangefinder Camera Lenses to Other Cameras
Because many mirrorless system lenses have a similar lens-flange-to-sensor distance, it's possible to use adapters to fit rangefinder lenses to mirrorless cameras with smaller cropped sensors. This includes cameras from Sony, Olympus, and Panasonic, as well as Sony full-frame E-mount cameras. There are also adapters for fitting M-mount lenses to L-mount cameras from Leica, Sigma, and Panasonic. Conversely, it's possible to use adapters to fit numerous other lenses to Leica M-mount cameras.
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