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How Do They Do It?
Outside of the infrared security camera lens is LED lighting (Light Emitting Diode), which lets the lens see a whole spectrum of light that our eyes can't see. The images captured are in black and white during any night filming. LED lighting gives the camera just enough light to film what's going on, but not enough light to be a dead giveaway to the subjects being filmed.
The eyes of any nocturnal creature come up of twin beacons of light, as the LED lighting is reflecting off of their eyes. But in even in very low levels of light (say, from the moon) the infrared security camera can often film in color. In regular levels of light, infrared security cameras will film in color.
There are some cameras on the market listed as "Day/Night cameras", but they are different from infrared security cameras. They don't use LED lighting but uses extra sensitive chips and are considered inferior in capturing good images for night time filming. To make things even more confusing, there ARE some Day/Night cameras that use LED lighting. Whatever the camera used for night surveillance, be sure it has LED lighting.
Advantages for Home Security
If you are considering an infrared security camera for your home or business, then it's best to get a weatherproof, round ("bullet") model. Be sure to install it outside. Remember how the light reflected off of nocturnal animals' eyes to make them glaringly bright? This can also happen if you install the camera indoors and it tries to film through glass.
Not all infrared security cameras are alike. Price will depend not only on shape and size, but also how far away they can film in total darkness. Think hard about all of the requirements you need in a security camera. Will there always be an outdoor light on somewhere? Do you get a lot of light from streetlights? In other words, if you really don't need to film in total darkness, there's no sense in spending the extra dollars and cents for abilities you're not going to use.