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COLOUR GAMUTS

1 / 3 · mockup · stairwell

COLOUR GAMUTS

sRGB, Display P3, Rec. 2020 and ProPhoto RGB on the CIE 1931 chromaticity diagram

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Premium$2.50

Payment and email are handled by Paddle. The download link arrives by email — no account, no password.

Formats
A4 · A3 · A2
What you get
Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject
science · comparison · everyone · study

The horseshoe is the chromaticity of pure spectral light; everything the eye sees lies inside it. The triangle is everything a space can describe. The share is a share of area on the xy diagram, not a share of colours: the diagram is not perceptually uniform.

THE WIDER THE GAMUT, THE FURTHER ITS CORNERS FROM REAL COLOUR

The three primaries of Rec. 2020 are not mixtures but pure monochromatic light: 630, 532 and 467 nanometres. Their coordinates from the W3C specification land on the spectral horseshoe to within a thousandth, and only a laser emits light like that.

In ProPhoto RGB the green and the blue lie outside the horseshoe altogether — 0.033 and 0.105 away from it — so they are not colours but points the eye sees under no light at all. Its triangle therefore covers 79.2 % of the horseshoe while occupying 82.9 %: the difference of 3.6 falls on what does not exist.

And the nesting the picture suggests is not complete: the red of Display P3 lies outside the red-to-green edge of Rec. 2020. A wider gamut does not mean the narrower one fits inside it.

On the sheet

  • The horseshoe is the chromaticity of pure spectral light; everything the eye sees lies inside it. The triangle is everything a space can describe. The share is a share of area on the xy diagram, not a share of colours: the diagram is not perceptually uniform.
  • Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
  • Nothing about how it was made: the sheet carries only what the reader needs.

Printing

  • Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
  • All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
  • White background and sparing fills — it prints on a home printer without draining the cartridge.
  • Margins of at least 10 mm: a home printer cannot print to the edge.
  • No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 7 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

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