In everyday language the Field of View of Field of Vision, abbreviated as FOV, refers to that area which is visible through any optical instrument, which could be the human eye or a lens.
This definition can be applied to the CCTV parlance and FOV can be defined as the width or height of a scene to be monitored by the security camera. In CCTV Field of View depends on a number of factors such as the sensor format, the focal length of a lens, and the distance from the objects.
A simplified calculation for 1/4-inch CCTV lens can be made using the following formula:
W (horizontal width) = (distance) * 3.2 mm / (Lens Focal Length)
where 3.2 mm is the horizontal size of 1/4″ CCTV sensor (4.8 mm for 1/3″ sensor).
It is very important to use the right lens for desired field of view; otherwise the images on security cameras will not be satisfactory. CCTV security camera lens with fixed focal length are less expensive and give smaller distortions but do not offer flexebility in terms of field of view choices.
To choose a proper lens the CCTV designer should consider all parameters. Avoid using commonly available online lens calculators because for proper lens selection you should consider both camera installation height and object height. Without taking all these parameters in the picture, the calculation error can exceed 30%.
Using our CCTV design software (CCTV Design Tool or IP Video System Design Tool) you can see how modification of any installation parameter can affect the result.