Contrast Ratio is the color difference between the whitest white and the darkest black colors which a display can show. The contrast ratio can reflect the color difference of the luminance level on an image. The greater the contrast, the better the subtlety of colors can be displayed.

To measure the contrast ratio, the nit values of the brightest and the darkest parts of an image should be measured.

The contrast ratio is the sum of the two nit values divided by the darkest nit value.

Contrast ratio = nit1 + nit2 / nit2