Welcome to the
"Co-veillance" Section
of
Doktor Jons

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.


A Collection of Covert Considerations

It is vitally important when looking at a possible location for any camera, to actually observe, or at the very least interpret, what the ambient lighting conditions are likely to be like, throughout the day.

Office environments (for example) can often provide a mixture of tungsten and fluorescent fixed luminaires, supplementing any natural daylight that may come in through adjacent windows.

When installing any covert camera, it is imperative to ensure that none of the available light sources (remember the sun moves position throughout the day!!) can possible reflect off the hidden lens - trust Doktor Jon, a ‘twinkling optic’ can seriously ruin your day.

In general terms, PCB cameras with pinhole lenses need a higher level of lighting to produce a decent ‘noise free’
picture. Remember, also that colour cameras need more ambient light than an equivalent Black & White model.

As colour cameras are generally not Infra Red sensitive, (B&W cameras are) they are unable to ‘exploit’ any IR light which may be freely available from existing hot filament light sources, such as low voltage downlighters, or desk lamps fitted with tungsten bulbs. Modern low energy (fluorescent) bulbs are very low in Infra Red output.

If a decent industrial CCTV camera is to be used, there is absolutely no need to buy an expensive auto iris pinhole lens.

A standard manual iris optic, with the camera switched to the Electronic Iris (EI or Electronic shutter) function, will provide more than enough exposure compensation for practically any eventuality; having said that, this is one perfect example of where using a more sensitive camera will pay dividends (higher sensitivity = opportunity to close the lens' iris = higher optical resolution + much better depth of field).

 

Continued>

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