The scene anglethat a video camera lens can show on the monitor, like Diagonal Angle,Horizontal Angle and Vertical Angle, usually described in degree.
Focal Length (FL)is the distance from the center of a lens to the focal point (CCD sensor chip).FL, as well as the CCD chip's format, is the major factor to determine theangle of view of a lens. For example, a 6.0mm FL lens on 1/3" sensorformat has 56.8 degree of diagonal angle of view and a 5.0mm FL lens on1/3" sensor format has 66.9 degree. But, the same 6.0mm FL lens can see75.5 degree on 1/2" sensor format. The angle of view also varies a littledepending on the Manufacturer of the lens.
For 1/3" CCDchip camera, the following formula is a simple way to determine the focallength of a lens needed.
(Distance tosubject / Width of subject) x 4.5mm = Focal Length.
For example, if youwant to watch a subject of 5.5ft width at 10ft distance with a 1/3" CCDcamera, you will need a 8.0mm FL lens. That is, 10ft / 5.5ft x 4.5mm = 8.18mm.A 8.0mm FL lens mounted on 1/3" CCD camera will cover the subject you wantto watch