What is the difference between C-mount and CS-mount camera?
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Differences Between C-mount and CS-mount Cameras
C-mount and CS-mount are types of lens mounts commonly found in CCTV cameras, machine vision systems, and other imaging devices. They are used to securely attach lenses to the camera body and facilitate the proper optical alignment between the lens and the sensor. Despite their similarities, they have distinct differences that are important for compatibility and optimal imaging performance.
Key Differences
| Feature | C-mount | CS-mount |
|---|---|---|
| Flange Focal Distance | 17.526 mm | 12.526 mm |
| Camera Compatibility | C-mount cameras | CS-mount cameras |
| Lens Compatibility | C-mount lenses can be used on both C-mount and CS-mount cameras with an adapter. | CS-mount lenses can only be used on CS-mount cameras unless the camera supports adjustable back focus. |
| Adapter Use | No adapter needed for C-mount lenses on C-mount cameras. | 5 mm adapter ring needed to use C-mount lenses on CS-mount cameras. |
Detailed Explanation
Flange Focal Distance (FFD): The flange focal distance is the distance from the lens mounting flange to the image sensor plane. C-mount lenses have to bridge a longer distance to focus light onto the camera sensor, resulting in an FFD of 17.526 mm. CS-mount lenses are designed for a shorter distance of 12.526 mm. The difference in FFD is significant because it affects the compatibility of lenses with different camera mounts.
Physical Design: The threads used in both C and CS-mounts are the same, with a diameter of 1 inch and 32 threads per inch. However, because of the different FFDs, the mounts are not directly interchangeable without modifications or adapters.
Usage of Adapters: Since C-mount lenses have a longer flange focal distance, a 5 mm spacer or adapter ring is used when fitting a C-mount lens onto a CS-mount camera to make up for the shorter distance and allow proper focusing. On the other hand, there is no adapter available that enables a CS-mount lens to be used on a C-mount camera, because the lens would sit further away from the sensor than necessary, resulting in an inability to focus the image properly on the sensor.
Camera Compatibility: CS-mount cameras can use both C-mount and CS-mount lenses, the latter without any adapter, by adjusting the camera's back focus if necessary or using spacer rings for C-mount lenses. C-mount cameras are generally compatible with C-mount lenses directly, and they cannot use CS-mount lenses without an adjustable back focus feature.
In summary, when choosing between C-mount and CS-mount cameras and lenses, one must consider the flange focal distance and camera sensor compatibility. The proper pairing is vital for achieving sharp images and ensuring the system operates as intended. Understanding these differences allows for better informed decisions when selecting cameras and lenses for specific applications.