Contrast ratio expresses the difference between the brightest white and the darkest black a television can display at the same time, usually written as a ratio such as ten thousand to one. A higher contrast ratio generally means a picture with more visible depth and punch, since bright and dark elements of the same scene stand further apart from each other.
Self emissive displays such as OLED can turn individual pixels off entirely, giving extremely high, effectively near infinite contrast ratios in ideal conditions. LCD based televisions depend on how well their backlight can dim behind dark areas, so technologies like full array local dimming with many zones improve contrast ratio considerably compared with a simple, uniformly lit backlight.
Manufacturer quoted contrast figures are not always measured the same way between brands, so they are best treated as a rough indicator rather than an exact, comparable number. Real world factors such as room lighting and screen reflections, covered in our entry on reflections and glare, also affect how much contrast a viewer actually perceives.
