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Guide to Closed Circuit TV (CCTV)

So would you like to play "Spot the CCTV Camera?". Eagle eyed visitors may recognise the profusion of street furniture, surrounding a single heritage dome camera keeping watch over part  of Londons' prestigious Oxford Street shopping area.

Making light of a dark place ...
the inside track on Infra Red.

Top Ten 'Must Know' things about Infra Red

Over the last few pages, we've looked at various aspects of using Infra Red lighting to achieve the highest quality images at night. Here in no particular order are a few more points worthy of consideration.

1) As light frequency increases above 685nM, it becomes invisible to the human eye, but some CCTV cameras can work up to 1200nM!!
2) Colour CCTV cameras are actually fitted with an IR block filter to minimise their sensitivity to these particular frequencies of light.

3) Apart from modern Solid State Light Emitting Diode (LED) arrays, most hot filament bulbs are also extremely rich in Infra Red output
4) It’s generally better to slightly underpower a bulb; as over voltage can significantly reduce the life expectancy of any bulb.

5) Some IR illuminator manufacturers increase reliabilty by using a number of seperate bulbs (e.g. 4 x 50 Watt to achieve 200W output).
6) Using a ‘soft start’ circuit for any tungsten bulb will significantly increase its overall life expectancy; as will a night switching photocell.

7) Never place a tungsten filament IR lamp directly under a camera housing; as the heat rises, it will gently cook the camera.
8) If intending to run a low voltage illuminator from lead acid batteries, be aware that cell capacity will vary greatly with temperature and age.

9) When changing a tungsten halogen bulb, avoid directly touching the glass envelope, as the effects of sweat can seriously damage it.
10) If using two illuminators on a PTZ camera, ideally one should be a 'flood’ pattern for wide angle viewing, and the other ‘spot’ for telephoto.


If you would like to see further information on any aspect of using Infra Red, e-mail to:- info[at]doktorjon.co.uk

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