Cameras are key tools in digital security systems. The features and capabilities of cameras determine what the security system can act upon and/or record for future reference.

Type of Camera

A primary choice is whether to use digital or analog cameras. Analog cameras generally use interlaced scan, whereby they scan every other line of the scene on one pass, and the complementary lines on the next pass. This can result in fuzziness when recording moving subjects. Digital cameras tend to use progressive scan, which scans the entire scene in one pass, resulting in a clearer image.

Digital cameras also communicate by using Ethernet, by far the world's most widespread local area network (LAN) standard. In addition, they often feature Power-over-Ethernet (PoE), which eliminates the need to run separate power cabling to the camera location, thus reducing cost. This enables digital cameras to offer better reliability, a simpler installation, and lower net cost than analog cameras.

Camera Resolution

Another important factor in camera selection is the resolution of the image. Many analog cameras use a resolution of 352x288 pixels, about 0.1 megapixels. Digital cameras come in a range of resolutions. Megapixel cameras range from a megapixel (1 million pixels) to multi-megapixels, offering as much as forty times the resolution of analog cameras. This gives much more detail and clarity to each frame. Your chance of identifying what and who is in recorded video is much greater than with an analog camera.

One advantage of using high-resolution digital cameras to cover a scene is that you can achieve the required recognition capability with many fewer digital megapixel cameras than analog cameras. Depending on the size, geometry, and other aspects of the coverage area, one digital megapixel camera may be able to substitute for as many as a half-dozen analog cameras.

Camera Intelligence

The intelligence of digital cameras is another important factor in digital security systems. Analog cameras are typically "dumb" cameras in that they offer limited means of decision-making and control. Analog cameras may be used with fixed mountings, viewing the same scene constantly, or they scan in predetermined patters over a larger scene. Frequently, they are activated by motion sensors so that they do not have to record continuously.

Digital cameras offer greater functionality because they can be controlled in a great variety of ways by onboard or remote software to operate in response to events that take place within their field of view, or in response to events that happen elsewhere within the larger system of which they may be a part. For example, they may be set to recognize and zoom in to track faces or license plates, or to count people entering or leaving a secured area. They may also be controlled to record on the occurrence of certain "interesting" events within their view, or the scope of the system they belong to.

Digital cameras now have the intelligence to detect motion in software-defined areas of their field of view, and react to or ignore motion, depending on the region in which it is observed.

Integration of Audio and Video

The integration of audio and video at the camera may be significant in camera choice. In situations where the sounds at the time and location of an event may be important, such as retail, restaurant, or bank sites, the ability to record the sound in sync with the video may be necessary to establish what is happening. Likewise, a two-way audio capability may be useful for access control applications by allowing communications to the point of entry. Also, cameras featuring integrated audio and video eliminated the need for separate audio wiring to the camera site, reducing wiring cost.