As published in CCTV Focus issue 1 AUG/SEPT 99
Often I am approached and asked if I have seen a latest product , camera etc., the specs are quoted as “colour camera with sensitivity good down to 1.2 lux ” and so on. Or I get asked what’s the best camera now days. When you consider the years of experience, design, build, test & manufacture many products involve. Isn’t it amazing that an item can be compared simply as that one is a few dollars cheaper than another. For instance the amazing camera specification I get given, ” look at this; isn’t that a great camera its colour 470 TV lines, 1.3 lux sensitivity , DSP , 1/3 ” CCD camera and look at its size” . In years past I have had to put cameras and many equipment up against the specs. Often some where in the tests you get a glitch and say how do they get that. Its here where I begin to learn reality and to the average spectator the basis of my skepticism evolves.
I remember as a young tech trying to commission the installation of a Ground to Air Aviation Transmitter and the spec say it was to achieve a 50 db Signal to Noise. This wasn’t being achieved the best figures were lucky to be 40db. The 1st response was, is this equipment faulty, lets check on the standby. No its the same result , has the test equipment been calibrated recently. Yes still has a current calibration certificate. Can we confirm the results using a different technique and equipment batch, Yes we can. Well then is this Model or batch of equipment faulty and operating under expectation.
Further tests to equivalent systems proved this was a typical result. Well then what? Here my 1st lessons to take specifications beyond a one figure result came. The 50 db S/N is only possible at a predefined Bandwidth and therefore I was to filter out all other frequencies. In simple the analogy, if put to your vehicle was that your engine noise from the exhaust can not be more than the average voice ( for the sake of of simplicity we won’t ask what is the average voice). To test this the exhaust would have to be taken away from the engine by means such as extending the exhaust through a sound insulated wall. Eliminating all other noises except the exhaust. Then here you could compare to the specification not louder than the average voice.
As you can see with every statement or specification many questions and clarification may be implied. Sometimes the conditions of the specifications are not obvious to the purchaser. So in making any very large investment. Consider your immediate budget and your projected budgets. Read the specifications with all the implications. Find out the conditions of specs and do they vary between product. Put it to a physical test under the same operating conditions & understanding the operating conditions, will assist you in achieving the best value for your money.
On larger projects / investment you may need to use a qualified person capable of putting to the test and comparing your alternatives.
When comparing cameras , do they compare with the same lens same conditions. Are the test conditions typical or useful to your conditions In My experience I have found that the difference in lenses demonstrate different qualities in a camera. Having spent much time in the past looking for poor contrast in a camera that otherwise performed admirably with sensitivity in darkness that put my eyes to shame. I found that the lens was the contributing factor to giving poor contrast pictures, due to the sensitivity of the camera other factors had to be considered . Such as Light reflections and refraction in the lens which normally would be considered insignificant, but in this case causing effect now contributing to a problem for a camera sensitive enough for this to be a problem. Or due to the sensitivity of the camera iris leaves were mainly shut in good lighting and such leaf design was affecting the distortion results. Now as camera packages become more and more a package with little options to the user , it is more critical that the cameras are put on site under real test and comparison. Comparison tests should all be based around your specific needs. When it comes to budget don’t just look at the initial buy price consider ease of support installation. Will you get the next service personnel say to you its best you replace this part as its not economical to repair. In other words this could mean if you picked the typical system ( or this could even be if you selected a strong technical support team) then it could be maintained easier & more cost effective. Does your company want to invest in future technologies at all costs , or within reasonable ranges to other comparable systems.
As you can see Product selection is more than how cheap can I buy it, what one spec figure is, or does it have DSP (Digital Signal Processing).