Contrast Ratio is defined as the ratio of luminance or brightness between the brightest color (white) to the darkest color (black) that a display is capable of producing. It is expressed in ratio, a:b, where a is the brightest white and b is the darkest black.
Example: An LED Display has a contrast ratio of 1000:1. This means that the white image is 1000 times brighter than the black image.
Contrast Ratio affects our ability to see details in what is shown on a digital screen. We can see finer details if the difference between the light and dark areas is distinct. The higher the contrast ratio, the more details you can see on a display whether it shows a photo, text, or video.
A high contrast ratio should always be desired in any display, as poor contrast results to low quality content.