Types of lens mounts

In machine vision projects, you need to be familiar with the various lens mounts, depending on the camera being used. Some of these mounts are shown in the figure below.

What is a lens mount and why does it matter?

The lens mount is where the lens attaches to the camera body. This connection is mechanical, and in some lenses it is electrical too. Each mount has its own dimensions and distances. So a lens with a different mount won't fit your camera without a suitable adapter. To learn about the standards, read the Lens mount article on Wikipedia.

Check the quality of a lens before you buy it. All the light that reaches the sensor passes through the lens. A poor lens ruins the image even on the best camera. After quality comes focal length. The longer the focal length, the narrower the field of view.

In auto iris lenses, the iris is adjusted automatically. In manual iris lenses, you have to adjust the iris by hand. In that case, when the ambient light changes, the image is no longer properly exposed. A wide lens is chosen for its wide field of view. Telephoto lenses are chosen for viewing distant objects with a narrow field of view; they have a shallower depth of field.

The mount is not only about the physical connection. Each standard also defines the distance between the mount and the sensor. If this distance is not kept, the lens cannot focus at infinity. Sensor size matters too. The lens's image circle must be larger than the sensor diagonal.

There is a simple formula for choosing the focal length. Focal length is roughly the working distance times the sensor length, divided by the width of the field of view. With this formula, you get a good estimate of the lens you need before you buy.

RasaAndishan products use several different mounts. The photo finish Model 1000 uses a manual M42 lens. The RA⁠-⁠LSC⁠-⁠2566 line scan camera accepts Canon electronic lenses. For more help choosing a lens, RasaAndishan FAQ.