Closed-circuit television cameras are able to produce both images and recordings for surveillance purposes. They can be either video or digital still cameras. The CCTV camera was invented by Marie Van Brittan Brown.
Information about video cameras
Video cameras can be either analogue or digital, i.e. they work by sending analogue or digital signals to some storage device, like video tape recorder or desktop PC / laptop.
Analogue cameras are able to record straight to a video tape recorder: analogue signals are recorded as pictures. When the analogue signals are recorded, the tape must run at a very slow speed to allow continuous operation. The matter is that if you want to allow a 3-hour tape to run for 24 hours, you should set it to run on a time lapse basis about 4 frames per second. However, in one second, the scene can change dramatically – for instance, an individual can have walked 1 meter. But when the distance is divided into 4 snapshots, each frame will look like a blur unless the subject keeps relatively still.
Analogue signals can be converted into digital ones in order to allow storage of the recordings on a computer. To do so, the analogue video camera should be plugged directly into a video capture card in the PC, which will convert the analogue signal to digital. Such cards are relatively cheap, but the resulting digital signals will be compressed 5:1 to save the video recordings on a continuous basis.
One more way to store the recordings on a non-analogue media is by using a digital video recorder (DVR). It is similar in functionality to a computer with a capture card and video recording software. However, most DVRs developed for CCTV purposes represent embedded devices which require less maintenance and simpler setup than a PC-based device.
A number of DVRs also can digitally broadcast the video signal, thus operating as a network camera. In case a device allows broadcasting of the video but doesn’t record it, it is called a video server and is able to effectively turn any analogue video camera into a network TV.
Such cameras don’t require a video capture card, as they operate using a digital signal that can be saved directly to a PC, compressing it 5:1. In addition, DVD quality can be achieved with more compression, but the highest picture quality of DVD is slightly lower than the quality of basic 5:1-compression.
Uncompressed digital recordings take up a huge amount of hard drive space, so a couple hours of it can quickly fill up a whole hard drive. Although holiday uncompressed recordings look fine, you couldn’t run uncompressed quality recordings continuously. That’s why motion detection can sometimes be a workaround solution to record in uncompressed quality.
Nevertheless, if you use standard-definition video cameras, the quality of the recording will be poor because the maximum pixel resolution in most devices is 320,000 pixels (as for analogue quality, it is measured in TV lines, but the point is the same). Today multi-megapixel IP-CCTV cameras are emerging on the market – although very expensive, they are able to capture video images at resolutions of 1 to 11 megapixel. In contrary to analogue cameras, the details like number plates will be easily readable on the recordings. At 11 Mpix, good quality images can be made, allowing to distinguish each hand on a person. Thanks to the much higher resolutions available with those types of the cameras, they can be placed to cover a large area which normally requires several analogue cameras.
IP cameras, also referred to as network cameras, are either analogue or digital video cameras with an embedded video server, which has an IP address and can stream the video (and perhaps audio, too).
Since network cameras are embedded devices which don’t need to output an analogue signal, they provide for resolutions higher than analogue cameras. An ordinary analogue camera has a PAL (768×576 pixels) or NTSC (720×480 pixels), while network cameras may have quad-VGA (1280×960 pixels) resolutions.
Although an analogue or digital camera with a video server operates as a network camera, the image size of the recording is restricted to that of the video standard of the device. Nevertheless, it’s optics (lenses and image sensors) which determines the image quality, rather than video resolution.
Network camera is a very cheap way to arrange surveillance, as it only requires one network camera, Ethernet cabling, and one PC. It can also replace the whole CCTV installations (cameras for network cameras, tape recorders for DVRs, CCTV monitors for computers with TFT screens and specialized software. According to digital video manufacturers, it is much better to turn CCTV installations into digital video installations.
In the meantime, the debate continues over the merits and price-for-performance of network cameras in comparison with analog cameras. Some industry observers claim that a lot of analog cameras are able to outperform network cameras at a lower price.
Information about digital still cameras
You can buy these cameras in any high street shop and use them to take excellent pictures in most situations. The pixel resolution of the modern models has reached 7 million pixels (7 megapixels). There are even shoot models produced by Canon and Nikon that can boast resolutions over 10 million pixels.
With these resolutions and high shutter speeds, such as 1/125th of a second, you can take .jpg pictures on a continuous or motion detection basis which will capture not just everyone running past the camera scene, but even the faces of people driving past.
You can plug such cameras into the USB port of any PC (most of them today have USB capability) and take pictures of any camera scene. All you need to do is mount the camera on a wall bracket and point it in the desired direction.
Up-to-date digital still cameras are able to take 500 kb snapshots in the space of one second. These snapshots will then be automatically downloaded by the camera software straight to the PC for storage in form of timed and dated JPEG files. In the meantime, the images don’t need to stay on the PC for long – in case it’s connected to the web, the images can automatically be uploaded to any other PC across the globe.
In other words, you won’t need to lift a finger except to simply plug the camera in and point it in the desired direction. It can be the street outside your house, the entrance to a bank, or subway station.
Modern digital still cameras are made with in-built wireless connectivity, which doesn’t require USB cable – the images will be transmitted wirelessly through the walls to the PC.