Types of Camera Lens Mounts – C-Mount, CS-Mount, and M12 Mount (S-Mount)

Lens mounts are the mechanical interfaces that attach a lens to a camera and set the correct distance for focus.

Choosing the right mount is critical to ensure the lens can focus properly. Frequently asked first questions when building a camera is:

- Will my CS Mount Lens work with my C Camera Mount?
- Will my C Mount Lens work with my CS Camera Mount?
- What is the difference between a S Mount lens and a M12 lens?
- How can I use an M12 lens with a C / CS mount camera?

If you've wondered any of the above, you're in the right place! Below is a concise guide to lens mount compatibility. We’ll compare C-mount vs CS-mount lenses and M12 vs C/CS-mount lenses – highlighting key differences, compatibility issues, and use cases.

S M12-Montage C-Montage vs. CS-Montage

What is the difference between C and CS mount?

C-Mount vs CS-Mount Lenses

C-mount and CS-mount are both common screw-threaded lens mounts used in machine vision and CCTV cameras. They share the same thread size (1-inch diameter, 32 threads per inch), but the flange height (also known as focal distance FFD) is different. The flange focal distance is the distance from the mount’s shoulder to the camera’s image sensor plane. 

We believe the "S" in CS-mount means "Short" which explains why:
- C-mount lenses have a standard flange height of 17.526mm.
- CS-mount lenses have a 5mm shorter FFD of 12.5mm. This improves optical performance and/or reduces optical design complexity and cost.

C-mount vs CS-mount compatibility is therefore one-way: 

1.) A C-mount lens can only reach focus on a CS-mount camera if a 5mm spacer ring is added.

2.) CS-mount lenses CANNOT be used on C-mount cameras. Physically the lens will thread on, but because the CS lens is designed for a shorter distance, it will focus the image in front of the sensor on a C camera. There is no simple adapter to fix this – the lens just can’t be placed far enough forward to focus on the sensor.

M12 Lens Mount vs C-Mount vs CS-Mount Lenses

M12 lenses (also known as S-mount lenses) are miniature lenses with a 12 mm diameter thread (M12 x 0.5). They are widely used in compact board cameras.

Comparing an M12 lens vs a C-mount lens (or CS-mount) reveals major differences in size and standardization: 

Physical Size and Thread:
M12 lenses are much smaller. They use a metric M12×0.5 thread instead of the 1″-32 UN thread of C/CS mounts. The entire lens is often only a few centimeters long. This compact size makes M12 lenses ideal for small embedded cameras, but it also means they typically work with smaller image sensors up to about 2/3″ sensor formats.

In contrast, C-mount lenses are larger and can support sensors up to around 1″ or more. 

Flange Focal Distance:
Unlike C/CS, the M12 mount does not have a standardized flange focal distance. The distance from the lens to the sensor in M12 systems depends on the specific lens design and the lens holder used. Each M12 lens must be matched with a compatible lens mount holder and adjusted (typically by screwing in/out) to focus on the sensor.

Not all M12 lenses are interchangeable across different holders or cameras – you must ensure the mechanical back focal length and lens barrel length suit your camera’s mount. In other words, an M12 lens that works in one camera might not focus in another if the lens housing is different.

Mounting and Adaptability:
M12 lenses screw into small lens holders on the camera board (often secured with glue or screws once focused). These holders are sometimes called S-mount or board-mount holders. Adapters do exist to use an M12 lens on a C-mount or CS-mount camera. However, compatibility is not guaranteed.  In practice, if you attach an M12 lens with an adapter to a C-mount camera, it may not be able to focus to infinity or it might vignette since M12 lenses are designed for smaller sensors.

Always check the lens specifications and, if possible, test the combination before committing to an M12-vs-C/CS swap. In short, M12 vs C-mount/CS-mount lenses trade off flexibility for size and cost. 

A Machine Vision Camera and Lens Compatibility Table

Tabelle zur Kompatibilität von Kamerahalterungen

Die Anpassung eines Objektivs an die Fassung kann frustrierend sein, wenn Sie ein Objektiv gekauft haben und feststellen, dass es nicht auf Ihrer Kamera fokussieren kann. Wenn Sie mit diesem Problem konfrontiert sind, sind Sie nicht allein! Anhand dieser Tabelle zur Kompatibilität von Objektivanschlüssen können Sie feststellen, ob Sie versehentlich ein inkompatibles Objektiv für Ihre Kamera gewählt haben.

Tabelle zur Kompatibilität von C CS S-Mount-Objektiven

Für S-Mount oder M12-ObjektiveFür den Vergleich ist ein mechanischer Vergleich zwischen dem Objektiv, dem Objektivanschluss und dem Kameragehäuse erforderlich. Der mechanische Aufbau ist bei jedem M12-Objektiv anders, da dieser Anschlusstyp nicht genormt ist.


Bitte beachten Sie, dass diese Tabelle davon ausgeht, dass Ihre CS-Mount- oder C-Mount-Kamera keine künstlichen MBFL-Einschränkungen hat. Die Teledyne/FLIR/PointGrey Blackfly CS / C-Mount Kameras sind nicht Kompatibel mit allen CS- und C-Mount-Objektiven, sofern der IR-Filter nicht entfernt wurde.

Das Auflagemaß und der Durchmesser von M12 / S-Mount-Objektiven sind häufig nicht mit CS- und C-Mount-Kameras kompatibel, was dazu führt, dass die Objektiv-Mount-Kombination nicht fokussiert werden kann. Diese Inkompatibilität kann auch bei anderen M12-Objektivanschlüssen auftreten.

In conclusion, understanding these lens mounts will help you pick the right lens for your project. For a large-sensor, high-precision vision system, go with a C-mount lens (or CS-mount if using a smaller format and tight space). For ultra-compact or camera modules, M12 lenses offer unbeatable size and flexibility. And whenever mixing and matching mounts (like using adapters), double-check the focus and image quality to avoid surprises. With the proper mount, your camera will capture sharp images and you can fully leverage the capabilities of your lens and sensor combination!

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