The cam lens is similar to the lens of the humaneye and gathers the reflected radiation fromthe scene much like the lens of your eye or a film camera.the capacity of the lens is to gather reflected light fromthe scene and center it into a picture onto the CCTV camerasensor. A small amount of the light arriving at the scene fromthe characteristic or simulated brightening source is reflectedtoward the cam and blocked and gathered by thecamera lens.
When in doubt, the bigger the lens diameter,the all the more light will be accumulated, the brighter the imageon the sensor, and the better the last picture on the monitor.this is the reason bigger opening (measurement) lenses, havinga higher optical throughput, are better (and more expensive)than littler breadth lenses that gather less light.under great lighting conditions—splendid indoor lighting,outdoors under daylight the expansive gap lensesare not obliged and there is sufficient light to forma brilliant picture on the sensor by utilizing little diameterlenses.most feature applications utilize a settled central length (Ffl)lens.
The FFL lens like the human eye lens covers a constantangular field of perspective (FOV). The FFL lens imagesa scene with consistent altered amplification. A huge varietyof CCTV cam lenses are accessible with distinctive focallengths (Fls) that give diverse Fovs. Wide-angle,medium-point, and tight plot (telephoto) lenses producedifferent amplifications and Fovs. Zoom and varifocallenses can be changed in accordance with have variable Fls and Fovs.most CCTV lenses have an iris stomach (as doesthe human eye) to modify the open region of the lens andchange the measure of light passing through it and reachingthe sensor.
Contingent upon the application, manual orautomatic-iris lenses are utilized. In a programmed iris Cctvlens, as in a human eye lens, the iris closes automaticallywhen the brightening is excessively high and opens automaticallywhen it is excessively low, in this manner keeping up the ideal illuminationon the sensor at all times. Figure on top shows representativesamples of CCTV lenses, including FFL, varifocal,zoom, pinhole, and an extensive catadioptric lens for longrange outside utilization (which joins both mirror and glassoptical components).