A Brief History of CCTV Continued

There was another major hurdle for CCTV to overcome and that was the quality of the recorded image. In the early days both the live picture and the recorded image were little more than a blur. However with the introduction of CCD the quality of the live image measured in TVL (television lines) would improve dramatically from 200 lines to nearer 450 in only a few years. The problem here was that most systems were using a VCR (Video Cassette Recorder) that at best would record approximately 220 TVL which meant that that the recording was at best disappointing. Moreover you then had to bear in mind that a tape length may only be 3 hours long. This meant that if you wanted to record for 24 hours you would either have to change the tape 8 times or use time lapse photography. A moving picture comprises of a number of static images flashed before our eyes so quickly that our brains see them as one continuous image.

With time lapse photography instead of taking 25 images a second which we would see as a moving picture you may have to spread your images over the available tape which would lead at best a jerky picture and at worst now you see it now you don’t! The reduced quality recorded image quality coupled with time lapse meant that more often than not the pictures were all but useless. There were a couple of better systems available that came down from the broadcast industry. The best remembered was called Betamax but this product lost the market battle against the cheaper VHS and died. VHS did develop to become S-VHS which took recording levels to 400TVL. This was a great improvement although you still could not get away from the time lapse problem. Fortunately the computer industry was going to provide the solution.

The CCTV industry now looked toward the ever increasing capabilities of the computer industry where you could now convert your analogue image to a digital format and store it on a hard disk. The quality of the stored image was now very good although the original systems were expensive and difficult to use so that that they were only fitted to big budget installations. The change came when demand for more and more storage within the computer industry meant cheaper ways were found to manufacture storage and better ways to compress the image. Gradually these systems have become affordable. The result now is that the recorded image is often indistinguishable from a live image.

The theory has never changed, moving pictures have always been a collection of static images moved quickly to fool our brains into thinking there is one constantly changing picture. In Victorian times they had disks of pictures that were hand rotated and viewed through a lens to provide a constant moving image. If you think in these terms when you come to record even on a computer or DVR (Digital Video Recorder) you cannot go wrong.

Firstly there is the quality of the picture (file size) this is dependent on the quality of the supplying camera and your choice of the file size you wish your computer to record. Usually this is described as low, normal and high. In Victorian terms this was the quality of the picture

Next there is how many pictures you want to record per second, generally over 12 pictures a second is desirable to anything over 20 where we will see it as real time. Essentially in Victorian terns this is how fast you can turn the drum

Finally there is how long you wish to store the information for. Again in Victorian terms this equates to how big is the drum!

Obviously in a perfect world you would want a broadcast quality image (now known as D1) recorded at say 25 images per second for infinity. The restriction will be the size of your hard drive and how many cameras you have connected to it. You will have to make compromises in either reducing quality to CIF4 (similar to the old S-VHS) then down to CIF 2 or even CIF or you may decide to take fewer pictures per camera per second. So you can see that if you have the very best quality at the highest frame rate your recorder may only last hours where as you could use the lowest quality and take a picture every 10 minutes and claim to record for years. It is important to find out what the client wants.

There have been other innovations within the software that allow the recording quality or the quantity of pictures to be increased if movement has been detected by the camera that is a very useful tool in maximising the length or the quality of the recording

The future of the CCTV industry will be closely aligned with that of computer industry where innovations in hardware and software will further enhance performance. There is even now the possibility with advance analytics that cameras may even replace movement detectors within the alarm industry

The introduction of “smart phones” has made it possible to view your camera system from your mobile. This has all sorts of applications from checking on your children to pre warning an alarm key holder that there are still intruders on the site.

One thing that is for sure the future will incorporate many more cameras not fewer!