Contrast Ratio is a measurement of the difference in brightness between the whitest white and the darkest black within an image. A ratio of 300:1 means the brightest point in the image is 300 times as bright as the darkest point. A higher contrast ratio therefore means a larger difference in brightness.

Contrast ratio is of interest in two situations:
- Cameras: When recording an image (video, film, photography) # tvs, Monitors, etc.
- TV Monitors etc - When choosing or setting up a playback device (TV, computer monitor, etc).