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The National Institute of Standards defines Resolution as "the ability to resolve or see small details in an image. Resolution for CCTV cameras (as well as for TV monitors and recorders) is usually specified in terms of horizontal lines of resolution. Horizontal lines of resolution relates to the number of independently resolvable elements (small details) in three-fourths of the picture width." This is what is commonly referred to as the "three-fourths rule." TRUE CCTV manufacturers like VELTEK and our reputable competitors now use a Bench Test form widely accepted by our industry, or a resolution test chart, yielding a range between 460 and 480 TVL (TV lines) for high resolution color cameras. Using our CVC4160D specs as a frame of reference, the proper mathematical computation of TVL is: • Resolution of Camera chipset (actual effective Pixels): 768 h x 494 w • 768 multiplied by 494 = 379,392 total effective pixels • The square root of 379,392 is 615.95. This represents average usable horizontal pixels • 615 multiplied by .75 (three-fourths rule) = 461.9 TVL Every now and then, we run into lesser-known competitors who create the illusion that their high resolution color cameras are superior to ours by using a creative, but inaccurate, method of computation which yields results such as 576 TVL. These companies will take the resolution of their camera chipset (768 h x 494 w), then will take the 768 h and multiply that figure by .75 (three-fourths rule) to get 576 TVL. When compared side-by-side, the supposed 576 TVL does not appear in any way to be superior to any of our high resolution color cameras or those sold by other CCTV companies. When you see a company that claims to have a high resolution color camera with extraordinarily high TVL, review the camera specification sheets carefully and apply the industry-standard calculations listed above.
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