What is an infrared cut filter?

Colour CCTV cameras use a filter mounted on top of the CCD chip which is known as an IR cut filter. The colour cameras use this chip as the spectral response of the CCD chip is quite different to that of the human eye. The filter makes the spectral response closer to that which would be percieved by the human eye.

All types of cameras—fixed, fixed dome, PTZ, and PTZ dome—can offer day and night functionality. A day and night camera is designed to be used in outdoor installations or in indoor environments with poor lighting.

A day and night, color camera delivers color images during the day. As light diminishes below a certain level, the camera can automatically switch to night mode to make use of near infrared (IR) light to deliver high-quality, black and white images.

Near-infrared light, which spans from 700 nanometers (nm) up to about 1000 nm, is beyond what the human eye can see, but most camera sensors can detect it and make use of it. During the day, a day and night camera uses an IR-cut filter. IR light is filtered out so that it does not distort the colors of images as the human eye sees them. When the camera is in night (black and white) mode, the IR-cut filter is removed, allowing the camera’s light sensitivity to reach down to 0.001 lux or lower.

The IR cut filter can affect the sensitivity of the camera at night and therefore True Day and Night cameras have been developed which either have no IR cut filter or a motorised IR cut filter which moves out of the way of the CCD chip at night.

Day and night cameras are useful in environments that restrict the use of artificial light. They include low-light video surveillance situations, covert surveillance and discreet applications, for example, in a traffic surveillance situation where bright lights would disturb drivers at night.

An IR illuminator that provides near-infrared light can also be used in conjunction with a day and night camera to further enhance the camera’s ability to produce high-quality video in lowlight or nighttime conditions.