Contrast ratio is used for display devices, such as monitors or televisions, as a measurement between the darkest black displayable and the brightest white. A contrast ratio of 2,500:1, for example, means that the display is capable of displaying whites that are 2,500 times as bright as the darkest black.
There are generally two types of contrast ratios for a device: the static contrast ratio and the dynamic contrast ratio. When comparing devices, it is best to compare static to static and dynamic to dynamic for accuracy. Since companies determine contrast ratios differently, limit comparisons of ratios within the models of the same company only.