The Contrast Ratio is a display system ratio between the brightest white colour and the darkest black colour on the television screen. A high level of contrast ratio, therefore, is very much a desired aspect. The Contrast Ratio ratings that are provided by different manufacturers of their display devices are more of an academic information rather than for comparison because of the differences in terms of measurements, operations and other unstated variables. While some manufacturers favour measurements that isolates the device from the system, others take the room effect into account. Ideally, if the contrast ratio of images is equal to the contrast ratio of the device, it represents high contrast levels. Ambient light in rooms reflect on the on-screen television displays and thus reduce the contrast ratio. The contrasts displayed by a static, motion less image is referred to as the static contrast ratio while a dynamic, changing picture ratio is referred to as the dynamic contrast ratio, generally.

Display devices generally favour the use of the full on/full off measurement method for contrast ratios as this cancels out the room effect and thus results in an ideal ratio, as such. There is another system though, the ANSI contrast, where the measurement is done based on a checker board pattern test image wherein the luminosity values are simultaneously measured. The ANSI system has more realistic capabilities, but this test needs to be performed under an ideal room environment. Overall, the full on/full off method is best suitable for measuring the dynamic contrast whereas the ANSI method is suited best for measuring the static contrast ratio. Plasma TVs display better contrast ratios on screen.

Dynamic Contrast Ratio

A notable development in television technology in recent times has been the dynamic contrast ratio factor. In effect, this involves the underpowering of the backlight lamp for displaying dark images. This process gives the benefit of realising the true potential of the static contrast ratio, even when watched under dark room conditions. On the other hand, brightness generally refers to the on screen emission of the luminous intensity and is measured in candelas. Higher the candelas, brighter the screen. Televisions are marketed commonly by mentioning only the dynamic contrast ratio and this should not be compared directly with the static contrast ratio. Typically, the dynamic contrast ratios of a Plasma TV display and a LCD TV display differ largely in terms of quality as well as quantity.