C Mount Camera

A C mount is a type of lens mount commonly found on 16mm movie cameras, closed-circuit television cameras, and trinocular microscopephototubes. 
C-mount lenses provide a male thread which mates with a female thread on the camera. The thread is nominally 1.000 inch (25.4 mm) in diameter, with 32 threads per inch, designated as “1-32 UN 2A” in the ANSI B1.1 standard for unified screw threads. The flange focal distance is 17.526 millimetres (0.6900 in) for a C mount. 
Merely to say that a lens is “C-mount” says very little about the lens’ intended use. Unlike all other lens mounts, each of which is used for only a single format, C-mount lenses have been made for many different formats, the largest being 4 times as large as the smallest. The vast majority of C-mount lenses are built for the 8-mm and 16-mm film formats and the 1/3-, 1/2-, 2/3-, and 1-inch video formats, which corresponds to a range of image circles from 5 to 17 mm diameter, approximately. Some manufacturers have recently introduced lenses for the 4/3 inch / 1.3 inch format but these remain very expensive