| The function
of the lens is to collect light reflected from the scene and focus it into an
image onto the CCTV camera sensor. Most CCTV applications use a
fixed-focal-length (FFL) lens, which, like your eye's lens, covers a constant
angular field of view (FOV). That is, the FFL images a scene with
constant magnifiction. A large variety of CCTV camera lenses are
available with different focal lengths (FLs), which will provide different
FOVs. Wide-angle, medium-angle, or narrow-angle lenses produce
different magnifications and FOVs.
This handy FOV calculator will help you in detemining which
lens is right for your application. Simply enter the distance to the
object, camera format, and focal length of the lens. Click
"Calculate" to see the field of view you can expect with that lens.
It also works in reverse. If you know the field of view you need,
enter it in and the distance to the object along with camera format to find the
focal length you will need to get the field of view desired. | 
