HDTV Tutorial: Contrast Ratio

I have noticed that a large number of people have come to the HDTV Almanac as part of online searches for information about HDTV contrast ratios. I go into the subject in some detail in Professor Poor’s Guide to Buying HDTV, but here’s the quick overview.

Contrast ratio is probably the single most important performance factor in determining how you perceive the image quality of your HDTV. It is defined as the ratio of the difference between the brightest part of an image on the screen and the darkest. As a practical matter, it’s the bottom end that is most important. Some sets display “black” as a dark gray, while others have “black” that looks as deep and rich as outer space and that you could just dive right into it.

A solid, dark black is important because it is what gives the color on the screen its life. If the black level is gray, then the whole image will look faded and washed out, no matter how bright the colors may be. When you have a good, solid black, however, the colors “pop” from the screen and you get the nearly three-dimensional experience. And if you watch DVD movies, a good black is especially important; the average movie scene uses less than 25% of the maximum available light (a full white image), which implies that there is lots of dark or black content in many images.

Now, while contrast ratio performance is important, the contrast ratio specifications published by most manufacturers are useless at predicting performance. This is because the way they measure contrast ratio has nothing to do with the way that you actually watch images on a television. A lot of factors can affect contrast ratio performance, not the least of which is room lighting. For example, the black level of most plasma sets will look better than most LCD sets if you’re in a windowless room with all the lights turned off. If you’re in a room with strong ambient light — such as a family room in the afternoon with lots of windows — then the black level will likely look better on the LCDs.

If you want to find out how well a given model produces black, most reliable approach is to go and look for yourself. A few minutes at the controls will tell you all you need to know.