There are two basic night viewing methods that cameras use: image enhancement and thermal imaging. Both methods use infrared radiation (IR) to see in the dark. If you have seen black and white high contrast night vision images, then you are familiar with image enhancement technology. It allows you to distinguish facial features and identify people and objects with great accuracy. With thermal imaging, the subject appears in bright colors because the camera detection is based on heat.
Security cameras that use image enhancement technology collect tiny amounts of light and amplify them to the point that you can see images clearly in the dark. The light that is collected is called infrared light, which is undetectable to the human eye.
Surveillance cameras usually have built-in infrared illuminators, which make it possible to see far away at night. LED type illuminators are generally preferred over bulb type illuminators because they are small (smaller than a thumb tack), require little power, and have a long life span. Infrared LEDs can provide enough light for a security camera to capture high quality images, even in complete darkness. The more LEDs a camera has, the greater the intensity and longer the distance it will be able to see in the dark.
New Defender cameras use thirty-eight LEDs, allowing for 110ft of night vision.