Contrast includes the dynamic range of an image representation or between any two pixels. The dynamic range can refer to achromatic colors, for example the dynamic range between white and black, as well as to the hues of colors. The highest contrast is that between the lightest and darkest parts of a screen display.
Contrast is a measure of readability. The definition used for evaluation is the contrast ratio. A high contrast ratio does not necessarily mean good readability. Paper has a contrast ratio of 10:1 and allows for fatigue-free reading; high contrast ratios, on the other hand, can interfere with prolonged reading. Contrast can refer to projected representations with emitting colors, as in displays and projectors, or to the reproduction of printed text and images.