Contrast Ratio for Televisions & Monitors
Contrast Ratio is a specification given with most good televisions and monitors. It refers to the device's ability to reproduce different levels of brightness.
A higher contrast ratio is more desirable — 500:1 is quite good.
Unfortunately the contrast ratio specification given by TV manufacturers has become somewhat abused. There is a limit beyond which this specification loses significance, as further improvements aren't noticeable in the real world. Do not be too concerned with figures higher than 2000:1, and figures over 10,000:1 don't have much relevance at all.
Note: Monitors also vary in their ability to display levels of gray, i.e. their grayscale performance. This can also effect the detail in darker areas of the image.