CCTV - Low Magnification Video Lenses

Image: CCTV Lens



A CCTV lens is a simple lens that is economical because of the volumes in which it is manufactured. Normally contains an iris and the ability to change focus.

The CCTV lens comes in various camera formats from 1" down to 1/6". The larger format lenses have been designed to perform over a greater sensor dimension. One can always use a larger format lens on a smaller format camera, but tried in reverse, the outer field image quality will suffer.

Each lens has its particular minimum operating distance (MOD). This is the closest distance an object may be located from the lens and still be focusable by the lens. To work closer than this, spacers must be placed between the lens and the camera, and while the magnification will increase, so will aberrations.

A general formula relating lens operating characteristics (outside the MOD)

Magnification = focal length/working distance

And field of view = sensor dimension/magnification

Because the lenses are working at less than 1X, the limit of resolution is determined by the camera sensor.

The wizard looks at your type of camera mounting, then at a potential solution to satisfy your magnification requirements.

CCTV lenses are rarely used over 1X magnification, due to poor optical performance.

If you specified a CS-mount camera, only 1/3" format cctv lenses will be recommended, and they are limited in the number of different focal lengths available. If you have the 5mm spacer to convert to c-mount, change the specification to c-mount and your selection of available lenses will increase.

The chart below shows the range of focal lengths available for various camera formats. To estimate your focal length, go to the above list of "user inputs", and multiply the working distance X the magnification. Then go to chart and see if your estimated focal length is in the availability range for the camera format. If not, modify the object size or working distance. Remember, a larger format lens can always be used on a smaller format camera (with the exception of the 1/3" format camera, with a CS-mount, which can only use a 1/3" CS-lens).


CAMERA FORMAT AVAILABLE
FOCAL LENGTHS
DIAGONAL VERTICAL HORIZONTAL
1" C-MOUNT 12.5 - 75mm 16mm 9.6mm 12.8mm
2/3" C-MOUNT 4.8 - 75mm 11mm 6.6mm 8.8mm
1/2" C-MOUNT 3.5 - 12mm 8mm 4.8mm 6.4mm
1/3" CS-MOUNT 2.8 - 16mm 6mm 3.6mm 4.8mm