How to choose a correct CCTV Camera Lens for security camera

There will be a lot of specs in the box when we bought a new security camera. We will explains all about 2.33mm,3mm specs printed on every cameras.

A convex lens is used inside security cameras, the focal length is the distance between the center of the lens and the point at which parallel rays that incident on lens converges to make a sharp image focus of the lens. Focal length is measured in mm.

The camera with lower focal length have larger optical power than the one with larger focal length. The CCTV camera lens with larger focal length have higher magnification and narrow-angle of view, conversely, for shorter focal length, it will have less magnification and wider angle of view.Generally, 2.8mm,3mm,8mm,12mm or 50mm lenses are used in the security camera.

Field of view

Field of view is the area which the lens allow us to see, for a wider FOV, the focal length of the lens should be small.

CCTV Camera lenses have 2 type: fixed and varifocal.

Most camera will have an industry standard of 3.6mm lens which provides a 72 field of view. Shown below is a diagram showing a comparison of FOV of the common lenses.

Security camera produces images using CCD(charge coupled device) sensor chips, the size of the chip is normally 1/4”,1/3” or 1/2”. The chip size is larger, the image quality is higher.Below is the table relating focal length and CCD size with view angle.