In 1973, Yashica the company began a collaboration with Carl Zeiss it called Top Secret Project 130 to produce a new, professional 35mm SLR with an electronically controlled shutter bearing the Contax name, and called the RTS (for 'Real Time System').
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Like Zunow, Yashica found it difficult to gain market acceptance with its proprietary SLR lens mount, and redesigned its SLR camera line in 1962 to accept the Contax/Praktica M42 lens mount.
They allow the use of P6 lenses on Mamiya 645, Pentax 645 and Contax 645 medium format cameras, Canon EF, Canon FD, Nikon F, Minolta AF, Minolta MD, Contax/Yashica, Pentax K, M42, and Leica R 35 mm cameras, as well as Lumix and Olympus micro 4/3 (m4/3), 4/3 system.