Gamut

The gamut of a colour space (or a display device) is the complete set of colours it can represent. Gamuts are usually visualised as triangles on the CIE 1931 chromaticity diagram — the corners are the red, green, and blue primaries of the space; the triangle’s interior is everything that can be produced by mixing them.

Gamut sizes, smallest to largest, for the spaces in active use:

• sRGB — the web default, 1996. Smallest of the modern gamuts.
• Adobe RGB — 1998. ~35% larger than sRGB, especially in the green-cyan region.
• Display P3 — Apple, 2015. ~25% larger than sRGB, more saturated reds and greens.
• Rec.2020 — ITU-R BT.2020, 2012. For 4K/8K HDR video. Substantially larger than P3.
• ProPhoto RGB — Kodak, 2002. Even larger; includes some colours outside the visible spectrum.

Colours that fall outside a target gamut are called “out of gamut.” Converting to the target either clips them to the nearest in-gamut colour (relative colorimetric) or shifts the whole image to preserve relationships (perceptual). The choice matters for print workflows; see our RGB vs CMYK comparison.

Worked example

You photograph a saturated red flower in Adobe RGB on a Sony A7R camera. The image looks vibrant on your Adobe RGB monitor at the office. You upload to Instagram and the reds look duller — Instagram displays in sRGB, and the saturated reds of the flower fall outside the sRGB gamut. The browser’s rendering engine clips those out-of-gamut reds to the nearest in-gamut sRGB value, shifting the hue slightly toward orange and dropping saturation. Now print the same image on a standard CMYK offset press: the gamut is smaller still — covering only ~70% of sRGB’s area, with biggest losses in the saturated greens and cyans. The flower’s red survives (CMYK can hit deep reds reasonably) but a saturated cyan sky in the same image becomes noticeably greyer. This is the gamut-compression chain every photographer fights: capture wide, edit wide, but always preview-soft-proof in the destination space before committing.

When and why it matters

Gamut matters whenever an image moves between devices with different colour capabilities. The mistake to avoid is editing in a wider gamut than your output medium and never soft-proofing — the final result will lose saturation in unexpected places. The opposite mistake is editing in sRGB for output that will go to a P3 display (Instagram on iPhone, Apple Photos slideshows) — you’ve already discarded the colour information the wider display could have shown. For web work in 2026, the practical workflow is: shoot in the camera’s widest space (Adobe RGB or ProPhoto RAW), edit in that space, export sRGB for legacy browsers and P3 for modern ones via Picture-element srcset with profile-tagged variants. For print, soft-proof in the destination CMYK profile (US Web Coated SWOP, FOGRA39, etc.) before approving the file. Reference: ICC — What is colour management?.

The four ICC rendering intents: when converting between gamuts, ICC profiles support four strategies. Perceptual compresses the source gamut into the destination preserving relative colour relationships — best for photographs. Relative colorimetric leaves in-gamut colours alone and clips out-of-gamut to the nearest valid value — best for logos and brand colours. Absolute colorimetric additionally preserves white point — used for proofing on a different paper white. Saturation maximises vividness regardless of accuracy — used for charts and infographics. Most software defaults to perceptual or relative; the choice rarely surfaces in user-facing UI but produces visibly different output.

The visible-colour boundary nobody represents fully: every RGB gamut is a triangle inside the horseshoe shape that bounds all colours the human eye can distinguish. Even ProPhoto RGB and Rec.2020 omit some saturated cyans and violets that real eyes can perceive. There’s no physical display technology that covers the entire human gamut — the corners of the horseshoe sit at single-wavelength monochromatic light, achievable only with lasers, which is why prototype laser-projection displays demonstrate richer colours than any LCD or OLED on the market. For practical purposes, P3 covers what most viewers can distinguish in a normal viewing environment. Related: chromaticity, Display P3. Reference: CIE 015:2018 — Colorimetry.