Colour contrast calculations for displays viewed in illumination

A procedure is described to assist the display designer to assess the role of luminance and chrominance in determining the ability of a displayed colour to withstand the effects of ambient illumination. Plots are produced for primary and complementary colours displayed on a colour cathode-ray tube to exemplify how to predict the contrast that exists between each colour and the achromatic background due to the display surface and the contrasts which exist when colours are overlaid. Although the example is for a cathoderay tube the procedure can be applied to other types of display technology and can be used to evaluate hypothetical designs prior to development.