The C-mount is mainly used to connect projectors and projection lens, as well as in some microscope imaging systems.
The distance from the mounting base plane to the focal plane of the C-mount is strictly specified to be 17.5 mm. This interface design allows a certain distance between the lens and the image sensor to achieve the best imaging effect.
The CS-mount is a ring used to increase the distance between the lens and the image sensor. It uses the ring to achieve the conversion between interfaces to achieve the best image presentation.
The original intention of the CS-mount was to help the lens present a clearer image, so the main difference between it and the C-mount is the distance between the image sensor and the lens. Specifically, the CS-mount shortens this distance to 12.5 mm, which is less than the 17.5 mm of the C-mount.
To use a C-mount lens with a CS-mount camera, you usually need to add a 5 mm spacer (C-CS connecting ring) to achieve the interface conversion.
简体中文 
English