35mm SLR · From 1949

M42 screw mount cameras

M42 is a 42 mm screw thread with a 1 mm pitch and a 45.5 mm flange distance. Carl Zeiss in Jena developed it in 1938, and it first appeared in 1949 on the Contax S and the Praktica, which is why it's also called the Praktica or universal thread mount. Pentax, Zenit, Fujica, Yashica, Mamiya, Olympus, Ricoh and Chinon all used it. Pentax's Spotmatic of 1964 metered through the lens with the lens stopped down, and Pentax moved to the K mount from 1975.

On the Spotmatic you push a lever to stop the lens down before the meter reads. The Spotmatic F of 1973 meters wide open, but only with Super Multi-Coated Takumars. An adapter puts M42 lenses on Pentax K bodies.

1 camera we cover.