10. Contrast: challenges and prospects

10.1 Definition and terminology

Contrary to what you might think, there are actually two very different notions of contrast for a given screen:

• ambient light contrast (CLA): this parameter corresponds to a screen used in a bright environment. It is particularly relevant for professional applications and public displays (station halls, etc.). This contrast, illustrated in figure 34 , is defined as the ratio between peak luminance and luminance reflected by the screen, both specular and diffuse. There are various standards for characterizing this parameter (VESA, FDPM, NF...