All types of network 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 network 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 graph shows how an image sensor responds to visible and near-IR light. Near-IR light spans the 700 nm to 1000 nm range.|
|Image at left, IR-cut filter in a day/night network camera; middle, position of IR-cut filter during daytime; at right, position of IR-cut filter during nighttime.|
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. More on IR illuminators.
|At left, image without an IR illuminator; at right, image with an IR illuminator.|
Next topic: Megapixel network cameras
© 2015 Axis Communications AB. All rights reserved