The Camera
Cameras convert the visible scene captured by a lens into an electric signal and transmit that signal to a
monitor for viewing.

Several considerations should be taken into account when choosing the proper camera/lens for any video system:

•	The purpose of the video system (detection, assessment, identification, ect.)
•	The overall sensitivity of the camera needed based upon the actual application
•	The amount and varying levels of light available at the scene
•	The environment in which the camera will operate (indoors/outdoors)
•	The field of view (FOV) required by the application (see figure 3)
•	The lens
•	Cost

Figure 3: Field of view.

Camera performance depends largely upon the reflected light at the scene and the quality of the
cameras imager (see figure 4).

Where the level of available light can change dramatically, a camera equipped with automatic iris
control can help assure consistent image quality. Automatic iris control enables cameras to open or close an auto iris lens to adjust the amount of light passing through the lens. On a bright, sunny day, for example, an auto iris camera will close the lens' iris to prevent strong light from reaching the camera's imager. At night, the camera will open the iris to allow a greater amount of light into the camera.

Cameras are available in various "formats" expressed as1/2, 1/3, or1/4 inches. These measurements represent the overall usable size of the camera's imager. In general, you should match the camera's
format to the lens format. For example, a half-inch camera should be paired with a half-inch lens.

Today, thanks to design improvments, high quality images are possible with smaller formats.

Figure 4: The imager (or chip).

Fixed and PTZ Cameras
CCTV cameras can be fixed or have pan, tilt and zoom (PTZ) capability. Fixed cameras are mounted on a fixed bracket and cannot move in response to operator commands. PTZ cameras are motor driven and can pan left and right, tilt up and down and zoom in and out for close-up or wide-angle viewing. (See figure 5)

Figure 5: PTZ camera.

A cameras housing protects the camera and lens from vandalism and the environment. It also can enhance the appearance of the camera installation and conceal the equipment from casual observation. All outdoor cameras require a housing of some type. The National Electrical Manufacturers Association (NEMA) rates housings on their ability to withstand environmental conditions. Protection from cold, heat, dust, dirt or other elements is needed to ensure optimum performance and extend the life of the camera.

Dome Cameras
Many PTZ cameras today are disguised in dark colored Plexiglas housings called domes. Dome cameras are found practically every major department store and in many industrial/commercial locations, hospital, colleges and government facilities (See figure 6). They are particularly popular wherever aesthetics are valued.

Dome cameras provide three primary benefits:

1) Deterrence	Domes make it virtually impossible for suspects to determine where the camera is pointed. Individuals planning to commit criminal activity are unable to detect whether or not they are under active surveillance.
2) Economy	Domes equipped with a camera, lens, and pan/tilt unit can be augmented with "drones" that have the same outward appearance, but have no equipment inside. The result is more apparent camera coverage with a much lower system expense.
3) Aesthetic Appearance	An exposed camera, lens, pan/tilt unit and associated wires are unsightly. A dome makes the collection of equipment more aesthetically acceptable, and does not detract from the interior design of a retail or business office environment.

Placing a mirrored finished or smoked bubble around the dome can conceal a dome camera further.

However, when this is done, the bubble has the effect of sunglasses, reducing the amount of light reaching the lens and affecting the color accuracy picked up by the camera.

Figure 6: Dome cameras.

On To The Next Section: The Lens>>