olemus
kuva või telepildi piirheleduste suhe
= the ratio of the luminance of the brightest shade (white) to that of the darkest shade

ülevaateid
https://en.wikipedia.org/wiki/Contrast_ratio
https://www.cnet.com/news/what-is-contrast-ratio/
https://digitalplacesolutions.com/wp-content/uploads/2014/04/Monitors_Contrast_ratio_WP_Aug081.pdf