“Encoding Colours: from the trichromatic theory to the electromagnetic signals” presented by Montaña

Encoding Colours: from the trichromatic theory to the electromagnetic signals

Keywords: Colour, RGB, YCbCr, Colour Vision, Technical Media, Trichromatic Theory, Standard Observer

Encoding schemes for producing, storing, and transmitting colour information in electronic media are based on a three-colour canon that originated in the 19th-century physiological studies of vision. During the 20th century this canon was first standardised and then implemented in technical media. Since then it has become ubiquitous for understanding and producing the sensation of colour. However, the precise technical operations to produce colours in electronic media has been usually overlooked in media history. This paper discusses how a certain interplay of scientific ideas, technical blueprints, and encoding specifications gave origin to the trichromatic theory and its implementation in electronic media. The first part of this paper happens in the scientific laboratories of the 18th and 19th centuries where the additive three- colour canon was set. The second part focuses on three implementations of this principle that have dominated electronic visual media ever since. These are: (i) the characterisation of a standard observer in the Colorimetric Resolution I by the Commission Internationale de l’Eclairage (CIE) in 1931, (ii) the implementation in of the NTSC color television during the 1940s and 1950s, and (iii) the ITU BT.601 recommendation for encoding digital video as a three-colour component signal from 1981.