Outdoor surveillance camera system on a construction site
Outdoor surveillance systems work in much the same ways as indoor systems; the main difference is the cameras. Outdoor cameras are designed to be weatherproof but outdoor cameras can also be used indoors. Typical surveillance systems have three major subsystems: the cameras (indoor and/or outdoor); a way to record the camera images, usually a security DVR; and a way to get the signal from the camera to the security DVR. Many systems can also be connected to the Internet for remote viewing and/or recording.
Cameras
Indoor camera in an outdoor housing
Outdoor cameras work just like indoor cameras except they are built to withstand the elements. These cameras can either be indoor cameras placed in water-tight housings or cameras that are completely enclosed and sealed from the manufacturer. Many cameras are designed to be used outdoors without a housing; these are often more economical and easier to install. Also, they are less obtrusive and typically less expensive; the consumer models can be purchased for less than $100 each. These cameras are usually called bullet cameras and the smaller varieties are called lipstick cameras (because they are the size of a tube of lipstick).
At Night
Because many outdoor surveillance systems are used at night, these systems have features to enhance nighttime surveillance. The most popular feature is called IR (infrared). IR cameras use small infrared LEDs (light emitting diodes) to illuminate the area in front of the camera with light which is invisible to the human eye. However, IR cameras do have some limitations.
IR Limitations
For many cameras, the actual field of illumination is often less than what is advertised. And although the IR light is invisible to our eyes, bugs can see the light and are attracted to it. Bugs attract spiders that build webs over the lens, causing glare and completely obscuring the night vision capability.
Low-Light Cameras
Cameras are rated in "lux," which is an illumination rating. The lower the lux rating of a camera, the better it can see in the dark. A camera rated at 3 lux is not usable in twilight and must be have additional lighting. And according to FootPrintSecurity.au.com, black-and-white cameras will function better in low light conditions because color cameras will produce a grainy image and become unusable. Professional-level outdoor security cameras can operate at lux levels below the human eye. A camera rated at .0003 lux can produce a usable image with just a partial moon and these cameras can be purchased for less than $150.
Camera Signal
The camera generates a signal which is transferred to a security DVR either wirelessly or through a cable. Coaxial cable-based systems are the most common and are called CCTV (closed circuit television) systems. Once the signal is transferred to the security DVR, it is recorded for future playback. Security DVRs are different than regular DVRs because they can record many cameras simultaneously and are enhanced with other features needed in surveillance situations.
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