Gamut Volume: How Much Color a Wide Gamut Actually Adds

An RGB device makes color by mixing three lights - a red, a green, a blue primary. Plot those three on the chromaticity diagram and connect them, and you get a triangle: every color the device can show lives inside it, and nothing outside can be reached. That triangle is the device's gamut. Its size and shape are set entirely by how saturated the three primaries are - push them outward and the triangle grows.

So "wide gamut" just means "more saturated primaries." sRGB uses fairly modest ones, covering about a third of the visible colors. Display P3 pushes the red and green out for a bigger triangle; Adobe RGB reaches further into cyan-green; Rec.2020 uses near-spectral primaries for an enormous triangle. But bigger isn't automatically better - the extra area is all saturated color, most everyday surfaces already fit inside sRGB, and the flat triangle hides that a real gamut is a three-dimensional volume.

Here they are, laid over the visible colors. Toggle each gamut and watch its triangle grow: sRGB sits inside P3, which sits inside Rec.2020; Adobe RGB reaches up into the greens. The corners are the primaries, and the space each triangle sweeps up is the color it can show.

Now put numbers on it. Divide each gamut's triangle area by the area of all visible chromaticities and you get a coverage percentage. sRGB covers roughly a third; P3 is about a third larger; Rec.2020 reaches well over half. These 2D figures are the common headline numbers - just remember they measure only hue and saturation, not the full story.

Coverage numbers are abstract; the interesting question is which colors a wider gamut adds. Subtract the sRGB triangle from a bigger one and what's left are the colors sRGB can't show - overwhelmingly saturated ones: vivid cyans and greens, deep reds, pure emerald and turquoise. Highlight the gap for each gamut. (On an sRGB screen these can only be approximated - your display may be showing them clipped.)

Turn it into a test. Pick a target chromaticity and the demo checks, gamut by gamut, whether it falls inside the triangle - a simple point-in-triangle test that any color engine runs constantly. Drag toward the saturated edges and watch sRGB drop out first, then P3, then Adobe RGB, with Rec.2020 holding on longest.

The terms of gamut size.

Six questions on gamut triangles, coverage, wide-gamut color, and volume. Instant feedback, no scores recorded - a wrong answer comes with a short explanation.

Gamut size sits between the chromaticity diagram, the RGB spaces, and gamut mapping - here's where to go next.