Different mechanical mounting systems are used to connect a lens to a camera, ensuring both good focus and image stability. The mount is defined by the mechanical depth of the mechanics (flange focal distance), along with its diameter and thread pitch (if present). It’s important that the lens flange focal distance and the camera mount flange distance are exactly the same, or focusing issues may arise. The presence of a threaded mechanism allows some adjustment to the back focal distance if needed. For example, in the Opto Engineering® PCHI series lenses, the back focal adjustment is needed to adjust the focus for a different field of view.
C-mount is the most common optics mount in the industrial market. It is defined by a flange focal distance of 17.526 mm, a diameter of 1” (25.4 mm) with 32 threads per inch.
CS-mount is a less popular and 5 mm shorter version of the C-mount, with a flange focal distance of 12.526 mm. A CS-mount camera presents various issues when used together with C-mount optics, especially if the latter is designed to work at a precise back focal distance.
F-mount is a bayonet-style mount originally developed by Nikon for its 35 mm format cameras and is still found in most of its digital SLR cameras. It is commonly used with bigger sensors, e.g. full-frame or line-scan cameras. Lenses can be easily swapped out thanks to the bayonet mount, but no back focal adjustment is possible.
Mxx-mounts are different types of camera mounts defined by their diameter (e.g. M72, M42), thread pitch (e.g. 1 mm, 0.75 mm) and flange focal distance. They are a common alternative to the F-mount for larger sensors.
Each camera mount is more commonly used with certain camera sensor formats. The most typical sensor formats are listed below. It is important to remember that these are not absolute values – i.e. two cameras listed with the same sensor format may differ substantially from one another in terms of aspect ratio (even if they have the same sensor diagonal). For example, the Sony Pregius IMX250 sensor is listed as 2/3” and has an active area of 8.45 mm x 7.07 mm. The CMOSIS CMV2000 sensor is also listed as 2/3” format but has an active area of 11.26 mm x 5.98 mm.
Common line scan sensors formats:
|2048 px x 10 µm||2048 px x 14 µm||4096 px x 7 µm||4096 px x 10 µm||7450 px x 4.7 µm||6144 px x 7 µm||8192 px x 7 µm||12288 px x 5 µm|
|20.5 mm||28.6 mm||28.6 mm||35 mm||41 mm||43 mm||57.3 mm||62 mm|
Common area scan sensors formats:
|Full frame - 35 mm||43.300||36.000||24.000|