Leica R bayonet
|A Leicaflex SL female part of in bayonet mount|
|Connectors||Electrical contacts for lens properties on later models|
The Leica R bayonet lens mount is the standard method of connecting a lens to the Leica R series of 35 mm single-lens reflex cameras. The mount is descended from those used for the Leicaflex, Leicaflex SL and Leicaflex SL2 SLR cameras, but differs in the cams used to communicate lens aperture information to the camera. 3 cam lenses are compatible with all of the Leica SLR cameras, while R-only lenses have a slightly different mount shape that will not fit on the earlier cameras.
The flange focal distance between mount and film is 47 mm.
The modern apochromatic manual focus Leica R lenses are especially notable for their world class optical performance[by whom?], for example, 90mm f/2 AA, 100mm f/2.8 Macro, 180mm f/2, 180mm f/2.8, and 280mm f/4.
On 5 March 2009, Leica announced plans to cease production of its R-Series manual focus SLR and lenses.
1 cam lenses have a sloped cam that only works to communicate aperture information to the original Leicaflex camera. They can be used on later cameras in stop-down metering mode only. Leica do not recommend that they be used on R8 or R9 cameras because if the cam is out of specification it may damage those cameras' ROM contacts. 1 cam lenses may be modified to work fully on later cameras.
2 cam lenses have two sloped cams for the Leicaflex, SL, and SL2. They can be used on R cameras in stop-down metering mode. As with 1 cam lenses, Leica does not recommend that they be used on the R8/R9 although they can be modified as with 1 cam lenses.
3 cam lenses have a third stepped "R-Cam" fitted that communicates aperture information to R-series cameras. They will work with all Leica SLR models since they have all three mechanical connections.
These lenses only have the stepped R-cam and only work on R-series cameras. The mount is deliberately slightly incompatible with Leicaflex models and will not fit. they may be converted to three-cam or ROM by a technician.
These only have the stepped R-cam plus electrical contacts allowing the lenses to communicate additional information to the camera, such as the lens' focal length. This is only supported on the R8/R9 although the lenses are fully compatible with earlier R cameras. The additional information is used in flash metering and communicated to the flash unit where it can be used to set power and flash zoom correctly and also to the optional Digital Module allowing lens focal length to be recorded with other image data.
Use with other cameras
The flange focal distance of 47 mm is fairly large, meaning that few other systems' lenses can be adapted to fit on a Leica R and retain infinity focus, but R lenses can be converted to other systems. The distance is only 0.5 mm larger than the Nikon F-mount, which is not sufficient to make a workable adapter, however, at least one Nikon camera has been modified with a Leica R bayonet mount to take R lenses, and at least two manufacturers make replacement mounts, allowing many Leica R lenses to be used directly on various camera systems, such as Nikon F mount cameras. Chips can also be attached to provide focal length and maximum aperture recognition in the camera body, which provides EXIF in digital cameras.
A number of manufacturers have produced adapters to allow Canon EOS cameras to take R lenses, these operate only in stop-down metering mode but function well when rapid operation is not required.