This mount is also called Universal screw mount, Pentax screw mount, Praktica screw mount, or M42 for short. Recently Cosina Voigtländer reintroduced a 42mm screw mount SLR with the Bessaflex TM (2004). The M42 mount was progressively replaced by bayonet mounts by all the manufacturers that used it, except on some Zenits. In the 1970s, as camera electronics and in-camera metering systems rapidly became much more sophisticated, requiring very accurate mounting tolerances to establish electrical contacts between a camera body and lenses, the technical limitations of a screw-mount lens system quickly rendered the M42 mount obsolete. Before screw-mount lenses faded from the scene, Mamiya, Pentax, Fuji, Olympus, Zeiss Ikon and Pentacon all introduced mutually incompatible systems to permit open-aperture metering but the majority of TTL metered M42 cameras simply use stop-down metering instead. All subsequent Pentacon 35mm SLR cameras (most of which were continuations of VEB Zeiss Ikon or KW lines) of the 1960s used the M42 mount.ĭespite the standardization of the diaphragm actuation mechanism, there was no industry standard for communicating the aperture ring position to a TTL light meter. In 1959 both VEB Zeiss Ikon and KW were absorbed into the new East German Pentacon camera manufacturing consortium. Praktica was once again an early adopter. By the early 1960s the diaphragm actuation mechanism had been standardized as many more companies began using the mount for their system 35mm cameras. Versions of this innovation were adopted by practically all subsequent users of the M42 mount (with the exception of preset or T mount lenses), though early adaptations varied slightly by manufacturer. In 1956 the Contax F introduced an internal aperture stop-down pin located at 6 o'clock inside the lens mount. It was also used by the Russians on Zenits from the second production run of the Zenit E onwards. In the 1960s several other Japanese manufacturers also adopted the mount for their new 35mm system cameras. Later (1957) it was adopted by Asahi for the Asahi Pentax family of SLRs which sparked the Japanese camera industry. In the early 1950s the mount was also used by the West German firm Wirgin on their Edixa Reflex range of cameras. It was also adopted by the East German firm KW on their Praktica range of cameras, introduced around the same time as the Contax S. The 42mm screw mount was introduced in 1949 with the Contax S 35mm SLR made by the East German firm VEB Zeiss Ikon. This page is NOT about the T mount thread measuring 42×0.75mm which screws into adapters ("T-rings") which fit many other types of SLR lens mount, first developed by Tamron. This page is about the 42×1.0mm thread M42 screw mount used to attach lenses to SLR cameras, most popular in the 1960s.
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