Color Gamut
The range of colors a device or color space can represent, drawn as a triangle of primaries inside the larger region of colors humans can see.
A color gamut is the set of colors a device can reproduce or a color space can encode. Because human vision is three-dimensional, colors can be plotted on the CIE 1931 chromaticity diagram, a horseshoe-shaped region containing every hue a person can see. A display with red, green, and blue primaries can mix only colors inside the triangle those primaries form. Everything outside it, such as the most saturated cyans and spectral greens, the display cannot show.
A color space fixes the triangle's corners, a white point, and a transfer function (the gamma or perceptual curve):
- sRGB (1996) matches the CRT phosphors of its time and covers roughly a third of visible colors. It remains the default for the web and for unlabeled images.
- Display P3 (from the cinema standard DCI-P3) reaches noticeably deeper reds and greens, about 25% more area than sRGB. Most modern phones and laptops support it.
- Rec. 2020 is the ultra-high-definition and High Dynamic Range target. It is so wide that few displays reach it fully, and it serves mostly as a container.
All three use a D65 white point, roughly 6,500 K daylight on the Color Temperature scale.
The space attached to an image has to be known. Pixel values are coordinates, not colors, and the same numbers mean different colors in different spaces. An untagged P3 image shown as sRGB looks dull. An sRGB image stretched across a wide-gamut panel without management looks garish, giving skin tones a sunburned cast. Operating systems and browsers perform color management, converting from the image's space to the display's. CSS can now express colors in wider spaces with color(display-p3 …) and oklch(), the latter also giving perceptually even steps for palette design.
When a source color falls outside the destination gamut, gamut mapping must choose a replacement. Clipping is simple but flattens subtle gradations. Compressing the whole range preserves relationships at the cost of overall saturation. It is the color equivalent of Tone Mapping, which does the same for brightness. Light sources have gamuts too: an RGB smart bulb's triangle is set by its LEDs, and color rendering describes how it lights other things. Good Color Contrast also depends on what the gamut can actually show.
See also3
HSL and HSV
Two rearrangements of the RGB color cube into hue, saturation, and lightness or value, made in the 1970s so people could pick colors intuitively, which are convenient for color pickers but don't match how bright colors actually look.
Graphics & Rendering6 connections
OLED
A display in which every pixel makes its own light from thin layers of organic compounds, giving true blacks and near-instant response, at the cost of limited full-screen brightness and gradual burn-in.
Graphics & Rendering5 connections
Image Format
The file formats the web uses for pictures, from the GIF, JPEG, and PNG generation to newer formats derived from video codecs, and the slow, politics-laden process by which a new one becomes safe to use.
Web Platform9 connections
Linked from4
- Color TemperatureMatter & Energy
Describing the color of white light by the temperature of a glowing ideal object that would emit it, from candle amber near 1,900 K to overcast blue above 6,500 K.
- HSL and HSVGraphics & Rendering
Two rearrangements of the RGB color cube into hue, saturation, and lightness or value, made in the 1970s so people could pick colors intuitively, which are convenient for color pickers but don't match how bright colors actually look.
- Image FormatWeb Platform
The file formats the web uses for pictures, from the GIF, JPEG, and PNG generation to newer formats derived from video codecs, and the slow, politics-laden process by which a new one becomes safe to use.
- OLEDGraphics & Rendering
A display in which every pixel makes its own light from thin layers of organic compounds, giving true blacks and near-instant response, at the cost of limited full-screen brightness and gradual burn-in.