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Is HDTV Contrast Meaningless?

August 21, 2006 | Author: Ibex Marketing

Almost every HDTV maker provides a rating for each model’s contrast. Contrast is simply a measure of how different the “blackest” black compares with the “whitest” white that the display can produce. Contrast is one of the most important performance factors for an HDTV, or any TV for that matter. Good contrast helps make the colors “pop”; poor contrast gives the image a washed-out look. The reason that you can’t read your cell phone display in bright sunlight is not that it lacks brightness so much as it lacks contrast.

So… if contrast is so important, then an HDTV that is rated at 10,000:1 contrast must be 10 times better than one rated at 1,000:1, right? Wrong. The manufacturer’s specifications actually are useless at predicting what sort of contrast you’ll experience when you install the set at home. The reason is that they use different methods of measuring. The most common method is to put the set in a blacked-out room, and then measure how much light comes off a totally black image. Then they measure the light from a totally white image, and do the math. The problem is that we don’t use HDTVs to watch all black or all white images in a dark room. (Network television is already boring enough as it is!)

There’s a better test, developed by the American National Standards Institute (ANSI). This uses a checkerboard pattern of black and white squares as the test image, and the average black level is combined with the average white level to calculate the contrast.

The news is that you don’t have to take my word for this. A display industry organization has published numbers that indicate just how much difference testing make. The Plasma Display Coalition was created by five major manufacturers to promote plasma HDTVs. They recently sent out a very expensive glossy booklet touting “the ultimate home entertainment experience.” But the meat of the matter was on the back page where they reported “Independent Test Results”.

These tests were done by Roam Consulting, headed by Peter Putman. I know Pete personally, and hold his professional work in high regard. He tested one plasma HDTV from each of the five companies, and the measures included contrast. The booklet doesn’t report the published specifications for the test models, but many plasma HDTVs are now rated at 10,000:1. Using the ANSI test procedure, however, the average contrast for the five test models was only 500:1. That’s the average, folks; this implies that some may have scored better, but only if some scored worse.

The bottom line is that you can’t trust the manufacturers’ contrast specifications when comparing different HDTVs, especially when comparing plasma agains LCD or rear-projection. My best advice is to trust your eyes, and know what to look for when comparing sets.