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CCTV Camera Basics
Video Surveillance Systems Buyers' Guide
There are a whole host of terms you might encounter for the first time when talking about CCTV systems with suppliers. Here's a brief explanation of most of them:
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CCD (Charge-Coupled Device)
A CCD changes the images viewed by a camera into electronic signals and transmits these through a cable to the monitor. In recent years, the widespread use of CCDs for imaging technology has reduced their price and improved their quality.
One of the specifications of a CCTV camera is in fractions of an inch, usually 1/4in or 1/3in, and represents the size of the image in the camera. A larger format won't necessarily produce a better quality picture but is useful in picking out detail in a badly lit area.
A high resolution camera of 450 - 500 TVL (television lines) gives you a more detailed picture but don't buy one without getting a suitable monitor to match. The average resolution of 350 - 400 TVL is fine for most purposes.
When you're making a decision about resolution, don't worry about any specification given in pixels: TVL is a more reliable guide to quality.
Signal to Noise Ratio
If you think of "signal" as image detail and "noise" as static, you want a camera that has a good signal to noise ratio (S/N or SNR) to avoid a grainy picture. The measurement is in decibels (dB) with 30dB delivering a poor quality picture and 60dB a first class image with virtually no static to be seen. 40dB offers you a reasonable picture for general surveillance use.
The lux rating of a camera tells you its sensitivity to light. A camera able to take acceptable pictures in an area with restricted lighting has a lower lux rating such as 0.5.
Black and White or Colour?
If you want to place a CCTV camera in an area where there is poor visibility, black and white may be best. But colour cameras are now more affordable than previously and some have a black and white facility if needed. These cameras are therefore becoming the most popular option, particularly as they show you the colour of a person's clothes or vehicle and thereby make identification so much easier.
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