Choosing a CCTV Camera

There are many styles of CCTV camera available but depending on the operational requirement, the best-suited camera should be selected. Fixed cameras in housings offer the ability to have larger lenses and wipers to clear away rain, whereas cameras in domes look more tidy and are generally cheaper. The same applies to pan, tilt and zoom (PTZ) cameras where an overt version has the ability to have larger lenses and have bolt on equipment such as a wiper and illumination that rotates with the camera. The dome versions have the same advantages as the static domes, i.e. tidy and generally cheaper but are limited if they have a tough operational requirement.

Cameras can produce colour images but colour viewing is limited by the amount of light that it needs to operate. There are digital signal processing techniques that allow a colour camera to see in relatively low light conditions but this processing has a price attached, which is often quality of image. Monochrome cameras see at much lower light levels and are sensitive to infrared illumination, which makes them ideal for night operation. To overcome the need for a colour camera during the day and a separate monochrome camera for nighttime, colour/mono or day/night cameras automatically switch from one mode to the other dependant on the available light.

Cameras can be categorized by their image sensors; the Charge Coupled Device or CCD chip is a light sensitive plate that converts the light focused by the lens into an electrical signal for processing. CCDs come in a range of technologies but the more basic criteria for categorizing a camera by its CCD chip is the diagonal size of the receptive area. The larger the CCD chip, the more light it can gather. In closed circuit television system CCD chip sizes are generally1/4”, 1/3” or 1/2”. The larger chips generally mean that the camera is more expensive.

The resolution of any CCTV camera is the key to the performance of the system. Resolution is the measurement of the picture quality in terms of how much electronic information is gathered. An analogue CCTV camera measures its resolution in Television Lines (TVL). These horizontal scans make up the video signal. The more horizontal scans there are in the image, the more detail the system captures and the clearer the resultant picture. The resolution is directly related to the number of pixels within the CCD chip. A low resolution camera would typically be around 330 Television Lines (TVL) and a high resolution camera would be from 480 to 540 TVL.

CCTV cameras also vary in the amount of processing that they do to the image before transmitting it to the control equipment. A high quality camera would have a range of processing features such as backlight compensation, which reduces the effect of silhouetting and automatic gain control to boost the video signal when light levels drop. For more demanding fields of view there are features that allow manual override of the shutter speed and wide dynamic processing. Wide dynamic processing allows the camera to produce high quality images in challenging conditions such as high contrast lighting produced by flood lights.

For true night vision there are thermal imaging cameras which detect very low heat sources and displays the image in a useable format.

When it comes to choosing the best CCTV camera the important considerations are around what you need to achieve based on the operational requirement.