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CCTV camera glossary


The following is a list of technical terms sometimes associated with CCTV cameras. Do not use it as a check-list when buying cameras, there are far more important factors to consider and to be honest we've already taken care of things when selecting which cameras to stock. We include it more to satisfy curiosity than anything else. Our new HD 1080P cameras have an on screen menu which allows you to fine tune the image and access some of the functions listed here.

AGC

Automatic Gain control. This allows the camera to maintain consistent images in varying light conditions. Different times of the day and different times of year will provide dramatically different lighting. AGC ensures a consistent image.

AES

Automatic electronic shutter. If you think of a normal stills camera to take a picture you adjust the shutter speed to vary the amount of light entering the camera. In bright light you need a fast shutter, in low light you need a slower shutter. With a CCTV camera  you don't have a physical shutter but an electronic equivalent. The longer it's "open" the more light that enters but also the more blurred the image.

BLC

Back light compensation. This is a clever feature that helps even out an image. Imagine you were standing in front of a window and someone took a photo of you. The camera would either choose you as the subject and the outside of the window would appear pale and washed out, or it would choose the outside as the subject and you would be too dark. Back light compensation helps avoid this and evens the picture out.

CDS sensor

This one is a bit of a cheat. Some places quote CDS as helping cameras see in low light levels. It's just the photo-cell which turns the Infra Red lights on, so every camera with Infra Red lighting built in will have a Cadmium Sulphide sensor! It's just a light switch and nothing to do with the camera CCD sensor or it's associated processing circuitry.

Infra-red lighting

Some of our cameras have built in infra-red lighting. At low light levels the small led's switch themselves on and the camera switches to black and white mode. You can't actually see infra-red lighting with the human eye (although you will notice a very slight red glow if you look at the led's on the camera). The camera picks up the infra-red light as it hits a surface and is reflected back, hence it can see in dark!

I/R cut filter

This is a mechanical device which slides an infra-red filter in front of the camera lens during the day to improve colour rendition. At night when the camera switches to black and white and the infra-red led's turn on the filter slides away. We don't generally favour I/R cut filters as they have a habit of failing either through age or environmental extremes (freezing conditions mainly).

DSP

Digital signal processing. This is the general term used to describe improvement of the initial image. It also incorporates additional features such as backlight compensation, motion detection and so on. This takes place on microchips separate from the CCD or CMOS sensor. Also referred to as the Chip set.

Dual CCD cameras

This is a solution sometimes used for cameras with built in Infra-red lighting. During the day the colour CCD is used to record images. When light levels fall the Infra-red led's turn on and the camera switches to a separate black and white CCD. This allows a high definition black and white CCD to be used. Whilst in theory you have the best of both worlds in practice you have twice the complexity and also twice the amount of setting up to do.

IP rating

This refers to how resilient the camera is to dust penetration and water penetration. It is quoted as a double digit number. The first number relates to dust protection and ranges from 0 to 6 with 0 offering no protection, 6 offering total protection. The second number refers to the level of water protection and ranges from 0, no protection, to 8, total protection from long periods under water under pressure. The numbers that interest us are 5 – protection against low pressure jets of water sprayed from all directions, 6 – protection against strong jets of water, suitable for use on a ship's deck, 7 – protection against temporary immersion up to 1m for periods of up to 30 minutes. In practice anything over IP65 is suitable for outside use. If you live in a lighthouse then you might want to up the ante to IP66 or even IP 67.

NTSC, PAL & Secam

For reasons best known to someone else there is no worldwide standard method of broadcasting television images. North America, half of South America and most of Asia use a format known as NTSC. We in the UK along with most of Europe, Australia, East Africa and parts of Asia use a system known as PAL. There is a third  broadcasting system called SECAM used in France, Eastern Europe and Western Africa. Normally SECAM televisions will also accept PAL signals but don't bet your life on it!

If purchasing equipment make absolutely sure it is compatible with your television system. NTSC and PAL do not work together.  All our products are sold as PAL versions so you will have no problems in the UK

There's a lot of information in this CCTV camera buyers guide and to be honest we've taken care of most of it for you in our choice of which cameras we chose to carry in stock. Decide what you want your CCTV system to do, choose a camera body type that suits your needs then select a lens combination that will work best in that application. If in doubt go for a zoom lens and you've got all the bases covered.