Kuribayashi's first interchangeable-lens 35mm SLR system.
THE CAMERA
The system consisted of a single camera, the Petri PENTA, introduced in 1959. It was a budget fully mechanical SLR with a quick-return mirror, fixed pentaprism viewinder, focal plane shutter with speeds ranging from 1/2 to 1/500th of a second, and a classic version of the M42 screw mount.
THE LENSES
The line of lenses released for this system was small, but it allowed photographers to shoot a wide range of subjects: from landscapes, casual photography and portraits, to wild nature photography. All lenses were of a preset type. The standard 50mm lens had a moderate speed of F/2, but was an unusually complex 7-element modified double Gauss design. The accessory lenses - 35/3.5, 105/3.5, 135/3.5, 180/3.5 and 500/8 - were designed and manufactured by Kyoei Optical Co. In the lens names, "C.C." or "K.C." indicated the type of single-layer coating.
Unlike other manufacturers, Kuribayashi did not follow the path of modifying the M42 screw mount to introduce the automatic diaphragm, but instead, already in 1960, released the Petri PENTA V camera with a proprietary breech-lock bayonet mount that supported the automatic diaphragm.