By: Jo Chew
Date: 16/2/2006

2.8mm, 4mm, 25mm, 50mm... What do these numbers mean? CCTV lenses are available with varying focal lengths. So how do you know which lens you need? I've constructed a table showing different focal lengths and the field of view in degrees that will be achieved.

There are alot of variables that determine the field of view that you will achieve. Such as the size of the cameras imaging sensor (usually 1/3 or 1/4 of an inch).

These figures are approximate, but should give you a good indication of what lens will suit your needs. The figures are approximate because monitor underscanning and other variables will affect the end result. Degrees are of the horizontal view of the camera.