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Guide to Closed Circuit TV (CCTV)

TRUSTED - Target Recognition Using Surveillance Technology for Evidence and Detection - A campaign to improve the effectiveness of existing video surveillance security systems.

CCTV Camera Operation - in a little more detail

CCTV Camera Controls

When it comes to producing a good quality picture, Doktor Jon has already mentioned that there are in fact six key areas to consider when looking at a CCTV cameras overall performance; and these are as follows:-

1) Resolution - How sharp an image can the camera produce?
2) Sensitivity - Can the camera perform well in poor lighting?
3) Exposure Control - Will the unit cope with variable lighting?
4) Lens Choice - Does the camera accept a particular lens?
5) Signal Output - Can the camera output the correct signal?
6) Environmental - Will the camera cope with the conditions?

The first, and perhaps most obvious consideration for any camera, is its ability to reproduce detail in the image, more commonly described as resolution.

For most modern CCTV cameras, the measurement which is most commonly applied is 'lines', although some manufacturers are a little bit naughty and insist on quoting 'pixels' which is not really a valid measure; all will be explained shortly!

Traditionally, since the birth of Television, (and indeed photography before that) engineers have sought to measure how much detail could be reproduced; and so any camera being assessed would be pointed at a test chart, and the resulting image reproduced on a high resolution test monitor.

By looking at the groups of closely spaced lines drawn on the chart, the last (most closely spaced) group that can clearly be defined in the picture, was taken as the 'limiting resolution', or nowadays simply 'resolution' for that particular model.

Doktor Jon should perhaps mention that almost all camera manufacturers quote a 'lines' figure which actually relates to the Horizontal resolution (i.e. the detail from left to right). Occasionally, some models will also list the Vertical resolution, in other words, the detail available from top to bottom in the picture. It is important not to confuse the two.


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