Contrast Ratio

Contrast ratio is one of the plethora of numbers that every single television manufacturer places prominently on the box of the TV they’re trying to sell. It’s too bad the number is pretty much meaningless.

Contrast ratio is a comparison of the highest and lowest values a screen is capable of producing. It tells you what range of brightness a TV is capable of displaying. It should tell you how subtle a TV’s picture will be.

Contrast ratio is important. The difficulty is that there are several different ways to measure contrast ratio. Each of them operates on a different scale. The lowest contrast ratios you’ll find these days are around 1000, and the highest are around 30,000. Does that really mean that one is 30 times better than the other? No. Because these values were produced using two different testing procedures. The lower one is a Static Contrast Ratio and the other is a Dynamic Contrast Ratio.

Static Contrast Ratio

A Static Contrast Ratio is a measure of how bright and how dark a TV can be at the same time. The TV displays a picture in which half the screen is pure white and half the screen is pure black, and then they measure how well the TV is able to show them. The trouble is that the dark half of the screen is affected by the light half of the screen. Little bits of light are reflected back onto the screen, or else the individual dots of light aren’t sealed well enough not to transfer light from one side to the other. The bottom line is that the dark half of the screen isn’t as dark as it would be if both sides of the screen were dark.

Contrast ratio is not only a measure of what the screen can do technically, but how well it’s constructed. A screen that’s built really well will insulate itself from itself so that light doesn’t transfer. It’s like a ‘pocket coil’ mattress. When the commercial shows a bowling ball falling on a bed that’s designed not to transfer motion, the other side of the bed isn’t disturbed, but you pay more for the better construction that doesn’t transfer the motion, just like you pay more for a screen that doesn’t seep light from one side to the other.

Dynamic Contrast Ratio

A Dynamic Contrast Ratio is the same thing, but instead of measuring dark and light at the same time on the same screen, a dynamic contrast ratio measures first dark, then light, sometimes on the same unit, sometimes using two separate units for each measurement. A dynamic contrast ratio produces a much higher number, because there is no bleeding of light, which results in much darker blacks.

A Dynamic Contrast Ratio is only a measure of what a TV is capable of producing, not a measure of how well it is constructed. A Static Contrast Ratio measures both at the same time, and is a much better test. Obviously, there are many factors which go into how these tests are performed, and how well the engineers are able to finesse the conditions to improve the results makes a big difference. Contrast Ratio should be viewed with the same skepticism as the gas mileage ratings that car companies put out. Those tests are performed in optimal conditions, and will not accurately represent real world experience.

At least for car manufacturers, though, there are rules to the test. For contrast ratio, the manufacturers can devise pretty much whatever test they want, and then tell you nothing about how they conducted the test, just throw out a number without context. Because of this, you shouldn’t pay attention to what the box says about contrast ratio unless it specifically states whether it was a dynamic test or a static test. If you’re unsure, ask to see the manual. Sometimes more information is given in the manual about the type of test performed, but remain wary of the contrast ratio written on the box. It’s probably just marketing hype.