Most security cameras come with night vision which allows them to still see things even when it’s dark outside. But how does it work?

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If you don’t know what we’re talking about, then you’ve probably at least seen the night vision footage from these ghost-hunting shows — that black and white or black and green look is all too familiar. Many security cameras are also equipped with the same night vision technology, allowing them to capture footage even in the dark.

Infrared night vision bathes the area in light that is invisible to our eyes

There are a couple of different types of night vision: one that is used by most security cameras and one that is used by night vision goggles. The most common type, which is used on most security cameras, is infrared (IR) night vision, which relies on infrared light.

If you’ve ever looked at the front of a security camera, you’ve probably noticed that it’s covered in a handful of little LED lights. This is infrared light, and when it gets dark, these lights turn on and act as a kind of spotlight, flooding the camera’s field of view with infrared light.

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The fact is that infrared light is completely invisible to the naked eye. So it doesn’t look like bright light is flooding the area outside, but it actually is — your eyes just don’t see it.

Also, night vision footage from CCTV cameras always appears in black and white because human eyes can distinguish black and white better than with other shades of colors such as red or blue. Because of this, most night vision cameras switch to a monochrome filter to make it easier for us to see the image.

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There are many different types of light that we can see with our eyes, but infrared (IR) light is invisible to the naked eye.

Most security cameras that have night vision capabilities, including the Nest Cam, also have what’s called an IR filter. This automatically detects daylight and applies a filter to block out IR light during the day to keep colors looking accurate. When nighttime arrives, the filter is automatically removed, allowing more light, including IR, from the camera.

Placing a night vision camera near a window will cause infrared light to reflect off the glass.
Placing a night vision camera near a window will cause infrared light to reflect off the glass.

The intensifier tubes absorb any light they can and amplify it

There is also another type of night vision, and it is more common in night vision goggles that contain something called «amplifier tubes». In the most basic terms, this involves the use of an extremely sensitive camera sensor that increases the intensity.

In more advanced terms, the available light that enters the night vision goggles (composed of photons) is converted into electrons, turning the light into a kind of electronic signal. The electrons are then multiplied with photomultiplier tube and then passed through a phosphor screen which creates flashes of light resulting in a brighter image.

All colors of light entering the goggles are converted to a green tint after passing through the phosphor screen, providing that iconic look you’re probably familiar with — human eyes are much more sensitive to green than most other colors. ,

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Night vision goggles are possible because it’s never dark outside, just very, very dark. In fact, it’s very hard to block the whole light unless you are actively trying to do so. Night vision goggles can pick up faint light from the moon or street lights and amplify it.

A normal camera can do something similar. Enter a dark room in your house (or go out at night) and take a long exposure photo with your camera (if it’s capable of taking long exposure shots). The resulting image will be much brighter than what you actually see because the camera takes all the available light and amplifies it. If there was absolutely no light available, the camera couldn’t capture anything, no matter the exposure.

Again, however, this type of night vision is usually only found in night vision goggles, and most security cameras that are equipped with night vision capabilities rely on IR light, which is much cheaper to implement and gives you better image quality overall.

Image courtesy of thekirbster/Flickr.

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