The Color Authorities

The map has a shape. The science layer defines what color is: the CIE owns the observer, the illuminants, and the difference math, with ISO/IEC ratifying and the IES extending it into light quality. The engineering layer defines how color moves: ITU-R for broadcast, SMPTE for cinema and facilities, EBU and ARIB for regional practice, DCI and the Academy for Hollywood's pipelines, ICC for the desktop. The market layer defines what ships: VESA, CTA and the UHD Alliance turn the paper into badges, ports, and picture modes.

Authority flows one way. HDR10 doesn't define a nit: it cites ST 2084, which maps code values to candelas per square metre, which the CIE defines through photometry. When you trace any consumer logo far enough down, you always arrive at the 1931 observer.

At the ITU, a Question is assigned to Study Group 6; working parties collect written contributions from administrations and sector members, converge on a draft Recommendation, and member states approve it: diplomacy-grade process, which is why a BT number changes slowly and means so much. At SMPTE, a project runs inside a technology committee of member engineers, survives due-process ballots where every objection must be answered, and publishes as an ST. At the CIE, a technical committee is chartered against a single scientific question and may run for a decade before its report appears.

Consortia move differently: DCI, ICC, VESA and the UHD Alliance write among member companies and publish when the lawyers finish. Faster, but binding only as far as the market chooses. The trade is always the same: speed against weight.

Read 'Rec. ITU-R BT.2100-2' from left to right: a Recommendation, from the ITU's Radiocommunication sector, in the BT (broadcasting television) series, document 2100, second revision. The numbers are registration order: 601 came before 709 came before 2020, chronology, not hierarchy. 'SMPTE ST 2084:2014' is a Standard (vs. RP or EG), document 2084, 2014 edition. 'IEC 61966-2-1' is family 61966 (colour management in multimedia), part 2-1: the 60000s exist because IEC renumbered everything upward in 1997.

The pattern holds everywhere: prefix tells you the body and the document's tier; the number is a catalogue accident; the year is the edition. Once you can parse a citation, you can locate any claim about color in about ten seconds, and spot when a spec sheet is citing nothing at all.

Every document in this module imports the CIE silently. BT.709's primaries are xy chromaticity coordinates: CIE space. ST 2084 maps code to cd/m²: CIE photometry. TM-30 runs in a color-appearance space built on CIE data. ICC profiles meet in a D50 XYZ connection space. Even a VESA DisplayHDR tier is verified with instruments whose readings trace to the 1931 observer.

This is why the bodies never truly contradict each other about color itself: they are all speaking one language, defined in Vienna, frozen in 1931, and refined, never replaced, for nearly a century. (How that observer was measured is the CIE & Its Diagrams module; why it was possible at all is A History of Color.)

These thirteen are not the same kind of thing. The ITU is a UN treaty agency: member states, diplomatic pace, global reach. SMPTE and the IES are professional societies: individual engineers, accredited due process. The EBU is an operating union of broadcasters; the CIE a scientific commission of national committees. DCI is a buyers' club: its spec is really a purchase order with the force of every studio's catalog behind it. ICC, VESA, CTA and the UHD Alliance are vendor consortia: the companies that must implement the standard write the standard.

The taxonomy predicts behavior. Treaty bodies are slow and near-permanent; consortia are fast and mortal; societies sit between. When a fast body needs permanence, it hands its work up: DCI to SMPTE, HP & Microsoft to IEC, NHK & BBC to ARIB to ITU. Watch the handoffs and the whole map animates.

Watch one feature cross the whole map. Dolby's researchers fit a curve to human contrast sensitivity and propose the Perceptual Quantizer; SMPTE standardizes it as ST 2084 in 2014. Meanwhile NHK and the BBC design Hybrid Log-Gamma for live broadcast; ARIB standardizes it as STD-B67 in 2015. In 2016 the ITU canonizes both systems side by side in BT.2100. CTA's HDR10 label and the UHD Alliance's Ultra HD Premium certification package it for shelves; VESA's DisplayHDR ports the idea to PC monitors.

Five bodies, three layers, roughly thirty months from lab curve to logo: the fastest the ecosystem has ever moved, and the clearest demonstration of how it is supposed to work. The curves themselves are the Transfer Functions module; the verification math (BT.2124) is ΔE-ITP.

In 1996 two companies, HP and Microsoft, published a proposal describing the average CRT on the average desk: Rec. 709 primaries, D65 white, a piecewise curve near gamma 2.2. The IEC ratified it in 1999 as IEC 61966-2-1, and it became the assumed color of every untagged image, every browser, every operating system since.

It's the ecosystem's strangest success: a corporate white paper that outranks, in sheer installed base, everything the treaty bodies ever published. It is also a standing trap: the sRGB encode curve and a pure 2.2 display gamma differ measurably in the shadows, and 'which one does this monitor mean?' is a question a probe answers and a datasheet usually doesn't. (See Transfer Functions and Signal Range.)

The HDR labels are ecosystems, not colorimetry. HDR10 is the open, royalty-free baseline (CTA, 2015): BT.2020 container + ST 2084 PQ + ST 2086 static metadata, one grade, one set of numbers for the whole program, mandatory on Ultra HD Blu-ray. HDR10+ (Samsung and Amazon, 2017) adds scene-by-scene dynamic metadata per SMPTE ST 2094-40, licensed through HDR10+ Technologies. Dolby Vision is the fully private authority: dynamic metadata in the ST 2094-10 lineage, up to 12-bit precision, and Dolby licensing and certifying every link (mastering tools, content QC, chips, displays) end to end. One company running its own three-layer stack.

HDR Vivid is the newest player: China's answer, developed by the China UHD Video Industry Alliance (CUVA) and released in 2020, a dynamic-metadata HDR system backed by Chinese broadcasters, streamers and TV makers, positioned to do domestically what Dolby Vision does globally. The pattern to keep: every one of these formats rests on the same ITU/SMPTE/CIE paper underneath. The label changes the metadata and the licensing; it never changes what a nit is, and whichever badge is on the box, the panel still drifts, and only measurement says how far.

A standard defines correctness: ST 2084 tells you exactly what luminance code 520 must produce, forever, on every device. A certification samples a floor: DisplayHDR 1000 means a unit like this one once demonstrated 1,000-nit peaks, a gamut minimum, and a black-level maximum under the test spec. Ultra HD Premium and Filmmaker Mode are the same species: performance floors and intent-preserving defaults, licensed as logos.

Both are useful; neither is calibration. The badge says the panel can. Measurement says whether it does, today, at these settings, in this room, on this unit. That gap between capability and conformance is where a calibrator earns the fee.

A working shortlist. What is the observer, an illuminant, ΔE, CRI? CIE. What are the primaries, white point and curves for broadcast or streaming? ITU-R, BT series. The exact PQ math, HDR metadata, cinema encodings, SDI? SMPTE. Legal signal ranges and monitor grades? EBU. HLG's definition at the source? ARIB STD-B67. The theatrical target? DCI's DCSS, engineered in SMPTE RP 431-2. Scene-referred pipeline? Academy ACES. Device-to-device management and the profile on disk? ICC. Light-source quality? IES TM-30 and CIE. What HDMI is actually signaling? CTA-861. What the badge on the box guarantees? VESA and the UHD Alliance.

When two sources disagree, prefer the higher layer and the newer edition, and check that anyone quoting a number can name the document it lives in.

Here's the part musicians already understand. Concert pitch is a standard too: ISO 16, first issued 1955, fixes A above middle C at 440 Hz. An orchestra doesn't vote on pitch each night; it tunes to the reference, and from then on any sour string is instantly, physically audible to a trained ear. Nobody argues with the wince.

Color works the same way. D65, ST 2084, BT.709 are the industry's 440 Hz, and to a trained eye, a display or a grade that has drifted off them produces exactly that wince, before any probe comes out of the case. Calibration is tuning: not a matter of taste, but a return to the published reference, verified by measurement. The authorities on this page keep the pitch.

We tune the instrument.