Lesson plan
C mount
A C mount is a type of lens mount commonly found on 16 mm movie cameras, closed-circuit television cameras, machine vision cameras and microscope phototubes. C-mount lenses provide a male thread, which mates with a female thread on the camera. The thread is nominally in diameter, with 32 threads per inch (0.794 mm pitch), designated as "1-32 UN 2A" in the ANSI B1.1 standard for unified screw threads. The flange focal distance is for a C mount. Merely to say that a lens is "C-mount" says very little about the lens's intended use. C-mount lenses have been made for many different formats. C-mount lenses are built for the 8 mm and 16 mm film formats and the 1/3", 1/2", 2/3", 1", and 4/3" video formats, which corresponds to a range of image circles approximately from 5 to 22 mm in diameter. Depending on the format, the design of the lens and its performance will differ considerably. For example, for the 4/3 format, a 12 mm lens is a wide-angle lens and will have a retrofocus design. For the 2/3-inch format, a 12 mm 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.…
Article summary
A C mount is a type of lens mount commonly found on 16 mm movie cameras, closed-circuit television cameras, machine vision cameras and microscope phototubes. C-mount lenses provide a male thread, which mates with a female thread on the camera. The thread is nominally in diameter, with 32 threads per inch (0.794 mm pitch), designated as "1-32 UN 2A" in the ANSI B1.1 standard for unified screw threads. The flange focal distance is for a C mount. Merely to say that a lens is "C-mount" says very little about the lens's intended use. C-mount lenses have been made for many different formats. C-mount lenses are built for the 8 mm and 16 mm film formats and the 1/3", 1/2", 2/3", 1", and 4/3" video formats, which corresponds to a range of image circles approximately from 5 to 22 mm in diameter. Depending on the format, the design of the lens and its performance will differ considerably. For example, for the 4/3 format, a 12 mm lens is a wide-angle lens and will have a retrofocus design. For the 2/3-inch format, a 12 mm 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.…
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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