Pekka Buttler, March 2023
History of the Leica R mount:
The German camera company Ernst Leitz1 of Wetzlar pioneered the use of 35 mm motion picture film in still cameras with the 1925 mass-market introduction of the Leica (LEItz CAmera). In 1932 an upgraded Leica was introduced to enable interchangeable lenses using a 39 mm diameter 28 tpi thread mount (what we today know as the Leica thread mount/LTM/L39 mount).
Most people associate the name Leica with marvellously designed and manufactured rangefinder cameras. But in the late 50s and early 60s the managers at Leica were paying close attention to the successful introductions of several Japanese SLR systems (e.g. Nikon F, Asahi Pentax, and Minolta SR) and reluctantly decided that Leica could not afford not to enter the SLR market.
Leica introduced the Leicaflex SLR in 1964, and because it could hardly have used Leica’s existing base of Leica M lenses (a flange focal distance of 27,8 mm is simply way too short to accommodate the mirror box of an SLR) Leica chose to introduce a proprietary lens mount for use with its SLRs. That mount is the Leica R mount (I’m guessing R stands for ‘Reflex’ just as M stands for ‘Messsucher'(rangefinder)).
It is quite clear that Leica approached the task of building a system of SLR bodies and lenses with their customary ambition and attention to detail, but in the fast-moving market, this attention to detail and finessing more often than not lead to Leica introducing cameras with a feature set that had been competitive 5–10 years earlier. Had the Leica SLR been able to compete on price, the market may have been forgiving, but competing on price simply is not in the essence of Leica. While Leica’s SLR business seemed to be a bottomless pit and as Leica was simultaneously stumbling in its rangefinder business, the company that had single-handedly introduced the concept of using 35 mm motion picture film for still photography seemed heading for bankruptcy.
In a move that surprised some, Leica staved off the impending doom through a strategic partnership with Minolta2, hence significantly decreasing development and manufacturing costs. As a result, the R3–R8 Leica models were co-developed between Leica and Minolta and shared many parts.
Development (versions) of the Leica R mount
While never proving the economic success Leica may initially have hoped for, the Leica SLR system became a relatively long-lived system, being officially discontinued only in 2009. Obviously, during such a long life-span, no camera that wants to position itself as a premium product can remain unchanged. As a result, also the Leica R mount has not stayed the same throughout. The five generations of Leica R lenses are quickly identified below:
1-cam
The original Leicaflex lenses (1964–1968) featured one sloped cam that communicated information on the selected aperture from the lens to the coupled (non-TTL) light meter.
2-cam
In 1968 the Leicaflex was upgraded to the Leicaflex SL, which featured through-the lens light metering. To accommodate the needs of the Leicaflex SL while simultaneously still supporting the original Leicaflex cameras, subsequent lenses were of a 2-cam design, with one cam to communicate selected aperture to the Leicaflex SL and another to do the same for the original Leicaflex. The Leicaflex SL2 (introduced 1974) did not necessitate changes to the mount.
3-cam
The introduction of the Leica R3 in 1976 however necessitated changes. As the selling point of the R3 was exposure automation, this necessitated information from the lenses – namely the lens’ maximum aperture – that the current 2-cam setup could not offer. Hence a third, stepped cam was added to the mount. Importantly – to this point – Leica always maintained backwards compatibility by adding new controls without depreciating older ones.
R-only
A limited number of lenses were subsequently offered as ‘for Leica R only’ (i.e. not compatible with Leicaflex’s). These lenses had only the third cam (and not the earlier cams needed by the Leicaflex/Leicaflex SL).
ROM
In 1996 Leica introduced the Leica R8, a thoroughly electronic/computerized SLR, that worked best when it was able to identify the lens that was mounted. As a result, A new generation of lenses was introduced that sported electronic contacts for more thorough communication between lens and camera. Problematically, as free space was running out in the Leica R mount, Leica was no longer able to implement additions without removing something older. Hence ROM lenses lack the 1st and 2nd cam and can therefore not be used on bodies prior to the R3. Conversely, it is not recommended to mount 1-cam or 2-cam lenses on the R8 (or its successor the R9) as these lenses may damage the electronic contacts on the body.
Leica R mount specifications
Mount type: Bayonet mount (lens release on camera)
Flange focal distance: 47,00 mm
Film format: 36mm x 24mm (‘Full frame’)
Mount communication:
• depending on lens generation (see above)
Adapting Leica R lenses
First, why would you want to adapt Leica R lenses? In the simplest terms, because Leica did not pull their punches in the designing of lenses for their premium SLR line. Leica R lenses have generally commanded a premium price – both as new and secondhand, and (thanks to their generous flange focal lens) have a long history of being used adapted on various brands of SLRs.
Leica R lenses can be used natively on Leica R mount cameras, but one should take care to match the compatible lenses and bodies. In the simplest terms:
• 1-cam lenses are fully compatible with Leicaflex cameras and can be used with stop-down metering on SL, SL2 and R3–R7 cameras. Using one-cam lenses on R8–9 cameras may damage the camera.
• 2-cam lenses are fully compatible with Leicaflex, SL and SL2 cameras and can be used with stop-down metering on R3–R7 cameras. Using two-cam lenses on R8–9 cameras may damage the camera.
• 3-cam lenses are fully compatible with any Leica R-mount camera (from Leicaflex to R9), but do not support the electronic features of R8–9 bodies without modification.
• R-only lenses are compatible with all R3–9 cameras, but do not support the electronic features of R8–9 bodies without modification. R-only lenses will not mount on Leicaflex, SL or SL2 cameras.
• ROM lenses are compatible with all R3–9 cameras, and do support the electronic features of R8–9 bodies. ROM lenses will not mount on Leicaflex, SL or SL2 cameras.
Leica R lenses can be adapted to any digital, mirrorless interchangeable lens cameras using a simple dumb adapter. Most Leica R–>[mirrorless mount] adapters will also mount any generation of Leica R lenses.
Leica R lenses also have a generous flange focal distance, that allows their adapting to a wide range of SLR/dSLR cameras (including Canon EF, Four Thirds, Nikon F, Pentax K and Sony A) with simple adapter rings. However, Leica R lenses adapted to dSLRS in this way will typically only work in stop-down metering. Moreover, some companies are offering conversions and conversion kits for permanently changing the mount of Leica R lenses into mounts that are still supported.
Footnotes:
1 Leitz (company) changed its name to Leica in 1986.
2 Minolta – as some might recall – is a Japanese Camera company that had initially been oriented towards manufacturing cameras through combing German and Japanese parts. Hence, one could think that a Leitz partnering with Minolta (of all Japanese camera manufacturers) was not such a great surprise…