Auto iris circuitry is normally linked to a motorized drive that opens and shuts the iris on the camera lens.Closing a physical iris is a much better way to protect a camera from being damaged by bright sunlight then simply using electronics to reduce the signal strength.
There are two main types of lenses used in security cameras.
The C mount lens has a flange back distance of 17.5mm.
Longer lengths give a narrower field of view and greater magnification.
The table below gives an approximate value for the angle of the field of view for lenses of various focal lengths and also considering the size of the imaging device (CCD).
The number of electrons, usually described as the pixel's accumulated charge, is measured, and then converted to a digital value.
This last step occurs outside the CCD, in a camera component called an analog-to-digital converter.
Security cameras with auto iris, have the ability to compensate for large variations in light levels.
This is useful for security cameras that need to adjust for changes from bright sunlight to darkness or night.
The cable used for normal CCTV installations is called RG59.
The encoded output of a surveillance camera whereby the red, green, and blue video signals are combined with the synchronizing, blanking, and color burst signals and are transmitted simultaneously down one cable.
When a video is recorded, the CCD is struck by light coming through the camera's lens.