This day and night camera delivers colour images during the day. As light diminishes below a certain level, it 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 700nm to 1000nm, is beyond what the human eye can see, but this camera sensor can detect it and make use of it.
During the day, a day/night camera uses an IR-cut filter. IR light is filtered out so that it does not distort the colours of images as the human eye sees them. When the camera is in night mode, the IR-Cut filter is removed, which allows the camera's light sensitivity to reach down to low lux levels!