The three letters H, L and S represent the classic colour variables of hue, luminance and saturation. Regardless of such identification, the system provides a possible application of Henry Munsell‘s system to the colours created on television screens by the process of phosphorescence. (Detailed text)
The three letters H, L and S represent the classic colour variables of hue, luminance and saturation. Intensity (I), which would create an HIS system from the HLS system, is often used in place of luminance.
Regardless of such identification, the system provides a possible application of Henry Munsell‘s system to the colours created on television screens by the process of phosphorescence. The expression «phosphorescence» comes from the Greek «phosphoros», meaning «morning star» or «Venus». It could also be translated as the «carrier of light». The light effect — the phosphorescence in other words — is created when energy delivered in the form of an electron beam is first of all stored by substances on the screen (molecules) and then released in the form of light.
The coloured picture on a television screen is actually produced by using three light-absorbing and light-carrying molecules which are concentrated into tiny patches of approximately 0.2 mm diameter. When they glow, a particular type of additive light mixing — a partitive mixture — will occur, which is normally created using the three colours red, green and blue (RGB). This will be explained when we examine the associated RGB.
In the HLS system, colour-hue is identified by an angle which can vary in an entirely conventional way between 0 and 360. As with saturation, intensity is measured on a scale of 100 units, read off along the axial line between the black and white tips. (Saturation is extracted along the radial lines running from grey to the full colour.)
Naturally, the problem of mediation between purely numerical (metric) and chromatic (psychological) scales is still present in the HLS system. But then, nobody is perfect — not even the carrier of light.
Date: No exact date; the system was developed in conjunction with television technology.
Basic colours: Red, green and blue
Form: Double cone
Application: Colour-order for phosphorescent television screens
Related systems: Munsell — RGB
Bibliography: «Computer Graphics CAD/CAM Image Processing», Editrice il Rostro, Milan, 1981; David Travis, «Effective Color Displays», Computer and People Series, Academic Press, London 1991.