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CCTV cameras are designed to capture video, convert it into an electric signal, and then transmit that signal to a monitor for viewing and recording device for storage. For this reason, many business owners and individuals purchase them online and have them installed for security purposes, and to have peace of mind.
Several considerations should be taken into account when choosing the proper camera/lens for any video system, whether for your business or home. Ask yourself the following questions before speaking to a CCTV company:
- The purpose of the video system (detection, assessment, identification, etc.)
- 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
- The lens – Most standard cameras do not come with a lens!
The lux (symbol: lx) is the SI unit of illuminance (lumens/sq meter).
In specific applications, an auto-iris lens is insufficient for the level of light available. In such cases a different type of camera is required; a low-lux camera for instance.
These cameras have a lux specification to distinguish the light sensitivity between CCTV cameras. The lower the number, the more sensitive the camera is to light. A camera listed as having a lux sensitivity of 0 would be able to see in complete darkness (i.e., infrared camera – see below).
Where the level of available light can change dramatically, a camera equipped with automatic iris lens 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.
Dynamic range is the brightness sensitivity ratio of the CCD (charge-coupled device).
The wide dynamic range is essential for capturing image detail at all light levels. Traditional surveillance cameras are plagued by dynamic range problems in a typical 24 hour day, due to severe reflections, glare, car headlights, and direct sunlight.
Wide Dynamic Range cameras avoid this problem. This is done by capturing multiple exposures and combining them to form an image that more accurately represents the light levels of the scene.
Matching a camera’s format specifications
Cameras are available in various “formats” expressed as 1/2, 1/3, or 1/4 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 improvements, high-quality images are possible with smaller formats.
PTZ Pan, Tilt, & Zoom
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. Assuming that you plan to buy a CCTV system for video surveillance, the PTZ function should be an important consideration in your purchase decision.
Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light. The name means “below red” (from the Latin infra, “below”), red being the color of visible light of longest wavelength. Infrared radiation spans three orders of magnitude and has wavelengths between approximately 750 nm and 1 mm.
Infrared is used in night-vision equipment, such as CCTV surveillance, when there is insufficient visible light to see an object. The radiation is detected and turned into an image on a screen, hotter objects showing up in different shades than cooler objects, enabling the police and military to acquire thermally significant targets, such as human beings and automobiles.
Do note that IR radiation is a secondary effect of heat; it does not heat itself! “Thermal” detectors do not detect heat directly but the difference in IR radiation from objects. Different materials emit more or less IR radiation as temperature increases or decreases, depending on the composition of the material. For instance, smoke is more transparent to infrared than to visible light, so firefighters use infrared imaging equipment when working in smoke-filled areas.
CCTV Domes: Aesthetically pleasing surveillance.
Dome cameras are found practically every major department store and in many industrial/commercial locations, hospital, colleges, and government facilities.
According to the folks at Platinum CCTV, an online retailer of CCTV cameras, equipment, and software, 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.
Network (IP) Cameras
Digital transmission methods for better integration and video quality. Network cameras, also called IP Cameras as they use the TCP/IP networking protocol, have emerged to be the successor of traditional analog cameras. There are many advantages to using IP-based surveillance equipment which is not available to older analog systems.
The primary advantage is connectivity. In many cases, IP cameras may be directly connected to any existing computer network, whether it be wireless or wired.
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