See also CCTV Images CCTV Images CCTV cameras can produce images or recordings for surveillance purposes, and can be either video cameras, or digital stills cameras. ...

and Closed Circuit Television Closed-circuit cameras are often used to discourage crime Closed-circuit television (CCTV), as a collection surveillance cameras doing video surveillance, is the use of television cameras for surveillance. ...

CCTV images and recordings can be produced using video or digital stills cameras.

1. Video Cameras

Video cameras are either analogue or digital, which means that they work on the basis of sending analogue or digital signals to a storage device such as a video tape recorder or pc/laptop.

a. Analogue video cameras can record straight to a video tape recorder which are able to record analogue signals as pictures, but these devices are becoming obsolete as more cameras are being manufactured as digital devices.

If the analogue signals are recorded to tape, then the tape must run at a very slow speed in order to operate continuously. This is because in order to allow a 3 hour tape to run for 24 hours, it must be set to run on a time lapse basis which is usually about 4 frames a second. In one second, the camera scene can change dramatically. A person for example can have walked a distance of 1 meter, and therefore if the distance is divided into 4 parts ie 4 frames or 'snapshots' in time, then each frame invariably looks like a blur, unless the subject keeps perfectly still.

Analogue signals can also be converted into a digital signal to enable the recordings to be stored on a pc as digital recordings. In that case the analogue video camera must be plugged directly into a video capture card in the computer, and the card then converts the analogue signal to digital. These cards are relatively cheap, but inevitably the resulting digital signals are compressed 5:1 (MPEG compression)in order for the video recordings to be saved on a continous basis.

The results are almost as bad as using a time-lapse video recorder to record the analogue signals.

Video cameras are prevalent in society but the quality of CCTV images and recordings they produce are on the whole abysmal, and this applies even when the video camera is digital! One only needs to look at the cctv footage on America's Most Wanted website to see the poor quality of captured events.

b. Digital video cameras These cameras do not require a video capture card because they work using a digital signal which can be saved directly to a computer. The signal is compressed 5:1 although DVD quality can be achieved with no compression. However, saving uncompressed digital recordings takes up an enormous amount of hard drive space, and a few hours of uncompressed video could quickly fill up a hard drive. Holiday DVD recordings may look fine but one could not run DVD quality recordings on a continous basis. Motion detection is therefore sometimes used as a work around solution to record in DVD quality.

However, in any situation where video cameras are used, the quality is going to be poor because the maximum pixel resolution of the lenses in most of these devices is a mere 320,000 pixels (analogue quality is measured in TV lines but the results are the same); they generally capture horizontal and vertical fields of lines and blend them together to make a single frame; the maximum frame rate is normally 30 frames per second; and the resulting compression of 5:1 finally produces what looks like a dog's dinner.

IP cameras are simply analogue or digital video cameras that are capable of being connected to the internet with an IP address. They are good for the remote monitoring of situations, but otherwise their quality is the same as any other analogue or digital video camera. Very few people anyway have the time to sit with their noses glued to a screen to study a camera scene on a continuous basis.

2. Digital Stills Cameras

These cameras can be purchased in any high street shop and can take excellent pictures in most situations.

CCTV Images

The pixel resolution of these cameras are usually in excess of 4 million pixels - which is almost as good as seeing with the naked eye! Some point and shoot models like those produced by Canon or Nikon etc boast resolutions in excess of 6 million pixels! Image File history File links Capture_00953-front. ... Image File history File links Capture_00953-front. ...

At these resolutions, and with high shutter speeds like 1/125th of a second, it is possible to take jpg pictures on a continuous or motion detection basis that will capture not only anyone running past the camera scene, but even the faces of those driving past!

These cameras can be plugged into the USB port of any computer (most of them now have usb capability)and pictures can be taken of any camera scene. All that is necessary is for the camera to be mounted on a wall bracket with two screws and then pointed in the desired direction.

Modern digital stills cameras can take 500kb snapshots in the space of 1 second, and these snapshots are then automatically downloaded by the camera software straight to the computer for storage as timed and dated jpg files. The images themselves don't need to stay on the computer for long. If the computer is connected to the internet, then the images can automatically be uploaded to any other computer anywhere in the world, as and when the pictures are taken.

The user doesn't need to lift a finger except to simply plug the camera in and point it in the desired direction. The direction could just as easily be the street outside a house, or the entrance to a bank or underground station.

Digital stills cameras are now being made with in-built wireless connectivity, so that no usb cable is required; images are simply zapped through walls or ceilings to the pc.

"Beam me up, Scotty"!