C-mount and CS-mount are two common types of lens mount, they have same thread size but different flange focal distance (distance from the mounting flange to the image plane).
Difference:
| C-mount | CS-mount | |
| Thread Size | 1 inch (25.4mm) diameter with 32 threads per inch (0.794 mm pitch) | 1 inch (25.4mm) diameter with 32 threads per inch (0.794 mm pitch) |
| Flange Focal Distance | 17.526 mm | 12.5mm |
| Application | machine vision, microscopy, and certain types of industrial and CCTV cameras | surveillance cameras and some machine vision |
The "C" in C-mount stands for "Cinema", it was initially developed for 16mm cine cameras. The "S" in CS-mount can refer to "Short" for easy remember since it has shorter flange focal distance.
Compatibility:
| C-mount Camera | CS-mount Camera | |
| C-mount Lens | ✔ | 5mm adapter required |
| CS-mount Lens | ✘ | ✔ |
Picture will be out of focus if you use CS-mount lens on a C-mount camera. We tested some varifocal lens and it barely working by adjusting the focus, it may not fully use the lens and is not suggested.
QAREQU C60 microscope camera is C-mount, which is common in the industrial cameras.