Security Cameras that see in the dark
Humans have several great attributes, but seeing in the dark is not one of them. Human vision is limited to a small portion of the electromagnetic spectrum called visible light. It is possible for humans to see beyond this range by making use of equipment which allows us to capture non-visible sources of electromagnetic radiation known as infrared light.
Many CCTV cameras now have the ability to project infrared light using an array of LED illuminators. When this capability is combined with CCD sensors capable of recording the infrared light, you achieve what is reffered to as night vision.
CCTV security cameras with night vision capabilities allow you to see in total darkness. Many night vision cameras are capable of producing detailed video regardless of lighting conditions. When required, night vision security cameras automatically switch to infrared mode without the need of human intervention.
There are four important things to keep in mind when dealing with night vision security cameras. Distance, resolution, light pollution and sensor type.
Many cameras tout their ability to project infrared light at great distances. Before spending resources on a camera that boast such feats, keep in mind that even if a camera can illuminate an object that is far away, chances are you are not going to be able to make out what that object is (unless you are using a camera with a zoom function). It is better to spend your money on a higher resolution camera with a lower infrared capability.
A vehicle will need to be within 50 feet of a night vision camera in order to properly identify the make and model (forget about color with an infrared security camera, the car will always be a shade of green). A person will need to be within 20 feet of the security camera to make a proper ID.
Most security cameras with IR illumination will have a reach of at least 25 feet – therefore the focus should be on increasing the image detail (or resolution) in order to have a better chance of identifying the subject. Remember that the resolution of the camera must be matched by a recording device that has the capability of recording it. If your camera has 480 lines of resolution, and your Digital Video Recorder can only record 320 lines of resolution, you are loosing the benefit of the higher resolution.
The other issue is light pollution. Many outdoor areas are lit at night. Sometimes by pretty strong light sources. Be very careful not to place your night vision security camera near such light sources, as it will interfere with the sensors and could produce unwanted artifacts in the recorded video.
If you plan to use your night vision security camera in an unlit area, keep in mind that the infrared illuminators do produce a faint reddish glow which can be easily detected at short distances. They may not be the best solution for covert surveillance.
Night vision is a necessary feature for any outdoor CCTV application. When choosing your camera, make sure that it features built in infrared illuminators and a CCD sensor. Cameras equipped with CMOS sensors do not perform as well in the dark, therefore I would recommend that you steer clear of them for outdoor applications. Also look for a camera with an IP55 designation which indicates that the camera is well suited to be used in humid and dusty conditions.