While the human eye can only register light between the blue and red spectrum, a color camera's image sensor can detect more. The image sensor can sense long-wave infrared radiation and thus "see" infrared light. Allowing infrared to hit the image sensor during daylight, however, will distort colors as humans see them. This is why color cameras are equipped with an IR-cut filter -- an optical piece of glass that is placed between the lens and the image sensor -- to remove IR light and to render color images that humans are used to.

As illumination is reduced and the image darkens, the IR-cut filter in a day & night camera can be removed automatically to enable the camera to make use of IR light so that it can "see" even in a very dark environment. To avoid color distortions, the camera often switches to black and white mode, and is thus able to generate high quality black and white images.