Systems and standards
Colour gamut and wide-colour displays
A gamut is the range of colours a device can produce. Newer screens show stronger reds and greens than the old standard allowed.
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No screen or printer can produce every colour the eye can see. The range a device can manage is called its gamut. For twenty years nearly all screens aimed at one standard range, sRGB. Many phones, televisions and laptops now cover a larger one, known as Display P3, and can show noticeably more vivid reds, oranges and greens. Colours outside a device's gamut have to be approximated.
What a gamut is
Colour scientists plot all visible colours on a horseshoe-shaped chart. A screen's three primaries, its red, green and blue, mark three points on that chart, and the screen can show only colours inside the triangle they form. The purer the primaries, the bigger the triangle. Since the chart is curved and a triangle has straight sides, three primaries can never cover everything. Printers have gamuts of a different shape. They can print some cyans and yellows that a standard screen cannot show, and they miss many bright screen colours.
sRGB, P3 and beyond
sRGB was defined in 1996 by Hewlett-Packard and Microsoft, modelled on the television tubes of the time, and it became the default for the web. It covers only around a third of the colours people can see. Display P3, adapted from a digital cinema standard, is about a quarter larger and reaches stronger reds and greens. Most recent phones and many laptops cover it. A still larger standard for ultra-high-definition television, Rec. 2020, needs primaries so pure that few consumer screens yet reach all of it.
What it means in practice
A wide-gamut screen makes a difference only if the picture contains wide-gamut colour and the software knows which standard the file uses. Recent phone cameras save photographs in P3. Web pages can now ask for colours outside sRGB, with a fallback for older screens. When an image is shown without the right label, its colours come out wrong: an sRGB picture stretched to a wide screen looks garish, with skin too red. Showing an out-of-range colour on a smaller gamut means clipping it or compressing the whole image.
Sources and further reading
- Gamut on Wikipedia
- MDN Web Docs: color-gamut
- MDN Web Docs: color()
- Stanford Computer Graphics Laboratory: Gamut mapping
- W3C: A Standard Default Color Space for the Internet, sRGB
Original text by the Rang desk, written with AI assistance and checked against the sources above. Meanings of colour vary from place to place and person to person. If we have something wrong, tell us.