C Mount on M4/3

This group is for people who appreciate C-Mount 16mm and Super 16mm lenses and want to use them with Micro Four Thirds cameras like Panasonic GH1, GH2, GH3 & GH4, Olympus E-P5, the Blackmagic Cinema MFT/Pocket Cinema Camera (with adapters), or the Digital Bolex D16 Camera (native C Mount), whether these lenses are Super 16 cine or 2/3" or 1" format simple CCTV glass, please feel free to contribute and share.

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All about the lens format.

A C mount is a type of lens mount commonly found on S16/16mm movie cameras, closed-circuit television cameras, machine vision cameras and microscope photo-tubes.

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.

This is no trivial difference. For example, for the 4/3 format, a 12-mm lens is a wide-angle lens and will have a retro-focus design. For the 2/3 inch format, a 12mm lens is "normal" and can have a simple and fast double Gauss layout. For the 1/3 inch format, a 12-mm lens is long and can have a telephoto design.

Some TV lenses lack provision to focus or vary the aperture, so may not operate properly with film cameras. Also, some TV lenses may have bits that protrude behind the mount far enough to interfere with the shutter or reflex finder mechanisms of a film camera.