Terms

Colour-science glossary

A working glossary of 86 terms spanning light, CIE and perception through RGB, log, Y′CbCr, HDR, ACES, RCM and signal metadata — with search, categories and links to full chapters.

86 terms6 categoriesSearchCIE · ITU · ACES

In plain language

The glossary is not for memorising abbreviations; it helps identify which layer a term belongs to: physical scene, perception, RGB representation, video signal, rendering or display.

6 sections4 primary references

Quick reference

Definitions and numbers worth keeping in view

Terms

From light and CIE through HDR, Y′CbCr, ACES and Resolve.

86 terms with pipeline context

Search by term or definition, then jump to the full chapter where the concept is explained in context.

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Light and physics

Colour

A perceptual result of a spectral stimulus interacting with an observer and viewing conditions. Colour is not a ready-made RGB property of an object.

Full chapter

Light and physics

Light

Optical radiation capable of producing a visual sensation. Colour science cares about its spectral composition, not only total power.

Full chapter

Light and physics

Spectrum

A quantity distributed over wavelength or frequency. For light it shows how much energy is present across the visible range.

Full chapter

Light and physics

SPD

Spectral Power Distribution

Spectral power distribution of a source: how much power it emits at different wavelengths.

Full chapter

Light and physics

Wavelength

A physical property of periodic radiation. One perceived colour need not correspond to one wavelength; most stimuli are polychromatic.

Full chapter

Light and physics

Illuminant

A standardised or described spectral lighting condition used as a reference condition in colorimetry.

Full chapter

Light and physics

Reflectance

The fraction of incident radiation reflected by a surface. Spectral reflectance combined with the illuminant forms the spectrum reaching an observer or camera.

Full chapter

Light and physics

Metamerism

The condition in which different spectral stimuli produce the same or a very similar colour response under specified viewing conditions.

Full chapter

Perception and CIE

Tristimulus values

Three values describing a colour match in a defined three-component colorimetric system such as CIE XYZ.

Full chapter

Perception and CIE

Standard observer

A standardised model of human colour matching used by CIE for XYZ and chromaticity calculations; it is not a profile of one individual.

Full chapter

Perception and CIE

S/M/L cones

Three cone classes with overlapping spectral sensitivities in short-, medium- and long-wavelength regions. They are not literal B/G/R sensors.

Full chapter

Perception and CIE

Visual adaptation

A change in the visual system in response to surrounding illumination and brightness, making perception of a stimulus context-dependent.

Full chapter

Perception and CIE

Luminance, Y

A photometric quantity related to light intensity from a surface in a specified direction. In CIE XYZ, Y is related to photopic luminance; do not confuse it with Y′ luma.

Full chapter

Perception and CIE

Brightness

A perceptual attribute describing how much light an area appears to emit. It is not identical to physical luminance.

Full chapter

Perception and CIE

Lightness

A relative perceptual attribute of how light an object appears compared with a similarly illuminated white reference. It is not a synonym for brightness or code value.

Full chapter

Perception and CIE

Hue

The colour-appearance attribute by which an area is perceived as reddish, yellowish, greenish, bluish or a combination of these.

Full chapter

Perception and CIE

Saturation

Perceived colourfulness relative to brightness; it depends on viewing conditions and is not simply RGB distance from grey.

Full chapter

Perception and CIE

Chroma

Perceived colourfulness relative to the brightness of a similarly illuminated reference area. In interfaces, Chroma can also refer to Cb/Cr, which is a different technical meaning.

Full chapter

Perception and CIE

Chromaticity

A colorimetric description of colour independent of an overall luminance scale; x,y coordinates derived by normalising XYZ are a common example.

Full chapter

Perception and CIE

CIE XYZ

The CIE standard three-component colorimetric system, often used as a device-independent intermediate for describing and transforming chromaticities.

Full chapter

Perception and CIE

White point

The achromatic reference chromaticity a system treats as neutral white. Rec.709, sRGB, Display P3 and Rec.2020 normally use D65.

Full chapter

Perception and CIE

D65

A CIE standard daylight reference widely used as the white point of television and computer RGB systems.

Full chapter

Perception and CIE

CCT

Correlated Colour Temperature

Correlated colour temperature: the temperature of a Planckian radiator whose chromaticity is closest to the stimulus under a defined rule. It does not describe the source's full spectrum.

Full chapter

Spaces and transforms

RGB

An additive three-component coordinate model. R/G/B values acquire colour meaning only after primaries, white point and encoding/transfer context are defined.

Full chapter

Spaces and transforms

Primaries

Reference colour stimuli whose mixtures describe other colours in the system. In an RGB space their chromaticities define the gamut geometry.

Full chapter

Spaces and transforms

Colour space

A defined coordinate system and rules that connect numbers to colour meaning. RGB systems normally require primaries, a white point and transfer/encoding context.

Full chapter

Spaces and transforms

Gamut

The set of colours a system or device can represent under defined constraints. Gamut is part of a colour space, not a complete synonym for it.

Full chapter

Spaces and transforms

Working space

The colour representation in which primary processing and grading operations are performed. It is chosen so transforms and tools behave predictably.

Full chapter

Spaces and transforms

Transfer function

A mathematical relationship between a physical/scene quantity and a signal, or between a signal and display light. OETF, EOTF, OOTF, log, PQ and HLG describe different parts of the chain.

Full chapter

Spaces and transforms

OETF

Opto-Electronic Transfer Function

The relationship between scene light or a camera exposure-like quantity and an encoded electrical/digital signal in a camera-side model.

Full chapter

Spaces and transforms

EOTF

Electro-Optical Transfer Function

The relationship from an encoded display signal to physical display light. PQ/ST 2084 is an EOTF.

Full chapter

Spaces and transforms

OOTF

Opto-Optical Transfer Function

The overall system relationship from scene light to display light, including rendering intent/system contrast rather than only one file encoding.

Full chapter

Spaces and transforms

Gamma

A power-law or approximately power-law class of transfer relationships. Interfaces often use Gamma more broadly for any transfer preset, which is technically imprecise.

Full chapter

Spaces and transforms

Log

A nonlinear camera/working encoding that allocates code-space precision across a wide range of scene exposure. Log is not a final display look.

Full chapter

Spaces and transforms

Matrix transform

A linear coordinate transform, for example between linear RGB spaces with different primaries. It does not automatically perform tone mapping or complex gamut compression.

Full chapter

Spaces and transforms

Chromatic adaptation transform

CAT

A model for transforming colour coordinates between different adopted/reference white conditions, approximating part of visual adaptation.

Full chapter

Spaces and transforms

Scene-referred

A state in which values retain a relationship to the scene/exposure before final display rendering. Scene-referred does not necessarily mean linear.

Full chapter

Spaces and transforms

Scene-linear

A scene-referred representation in which numeric values are proportional to a chosen linear light/exposure quantity. Important for physically meaningful compositing.

Full chapter

Spaces and transforms

Display-referred / output-referred

A state after colour rendering, oriented to the characteristics of a target display and viewing environment.

Full chapter

Spaces and transforms

Tone mapping

Redistribution of luminance/tone relationships to fit source dynamic range into a target display without simple hard clipping.

Full chapter

Spaces and transforms

Gamut mapping

Mapping colours outside a target gamut/colour volume into the available region while controlling hue, saturation and perceptual ordering.

Full chapter

Spaces and transforms

DRT

Display Rendering Transform

A rendering stage that turns a scene-referred representation into a display-oriented image; it can combine tone scale, gamut mapping and other perceptual decisions.

Full chapter

Camera and video signal

RAW

An early camera/sensor-domain representation that preserves more information and interpretation choices before full image rendering. RAW is not equivalent to log.

Full chapter

Camera and video signal

Debayer / demosaic

Reconstruction of full-colour RGB from mosaic/CFA sensor samples where an individual photosite usually measures only one filtered component.

Full chapter

Camera and video signal

Camera gamut

A manufacturer-defined RGB space/primary set used to represent camera colour after sensor processing, such as ARRI Wide Gamut or S-Gamut.

Full chapter

Camera and video signal

Camera Log

A nonlinear transfer encoding from a specific camera family, such as LogC or S-Log. It must be interpreted together with the matching gamut/generation.

Full chapter

Camera and video signal

White balance

A camera-side adjustment/interpretation that changes relative channel gains or an equivalent transform so a chosen neutral stimulus becomes neutral.

Full chapter

Camera and video signal

Y′CbCr

A digital luma/chroma representation: Y′ is a luma-like component derived from nonlinear R′G′B′, while Cb/Cr are colour-difference components. It is not a separate gamut.

Full chapter

Camera and video signal

Luma, Y′

A weighted combination of nonlinear R′G′B′ used in Y′CbCr. The prime matters: Y′ luma is not CIE Y luminance.

Full chapter

Camera and video signal

Cb / Cr

The colour-difference components of Y′CbCr, encoding blue/red-related differences from the luma-like component; neutral chroma sits at the code-range midpoint.

Full chapter

Camera and video signal

Matrix coefficients

The coefficient set used for R′G′B′ ↔ Y′CbCr conversion and associated with the signal standard. BT.601, BT.709 and BT.2020 use different weights.

Full chapter

Camera and video signal

Full range

Use of nearly the full available integer code range for image values. It is a quantisation/range property, not a separate colour space.

Full chapter

Camera and video signal

Video / limited / narrow range

A nominal digital range with reserved head/footroom; for example 10-bit luma black/white at 64/940 in typical Y′CbCr video representation.

Full chapter

Camera and video signal

Bit depth

The number of bits per sample/component, determining available code levels and quantisation precision. It does not by itself define dynamic range or gamut.

Full chapter

Camera and video signal

Quantisation

Mapping a continuous or more precise quantity to a discrete set of code values. Steps that are too coarse can appear as banding.

Full chapter

Camera and video signal

Chroma subsampling

Reduction of the spatial sampling rate of Cb/Cr relative to luma. 4:4:4, 4:2:2 and 4:2:0 describe sampling geometry, not bit depth.

Full chapter

Camera and video signal

4:4:4

Luma and chroma are represented on the full spatial sampling grid with no chroma subsampling.

Full chapter

Camera and video signal

4:2:2

Chroma has roughly half the horizontal sampling density while retaining vertical density relative to luma.

Full chapter

Camera and video signal

4:2:0

In a typical progressive representation, chroma sampling density is roughly half that of luma horizontally and vertically.

Full chapter

Camera and video signal

Chroma siting

The phase/spatial position of chroma samples relative to the luma grid. A 4:2:0 label alone does not fully define siting.

Full chapter

Camera and video signal

Codec

A method for encoding/decoding an image. A codec defines compression and representation details but does not replace primaries, transfer, matrix and range signalling.

Full chapter

Camera and video signal

Colour metadata / tags

Signalling fields telling a player/decoder how to interpret primaries, transfer, matrix, range and other properties. Tags do not transform pixel values by themselves.

Full chapter

HDR and displays

SDR

Standard Dynamic Range

A class of display/rendering workflows using traditional luminance ranges, commonly associated with Rec.709/BT.1886-style video viewing. SDR is not a synonym for 8-bit.

Full chapter

HDR and displays

HDR

High Dynamic Range

A capture/render/display system capable of reproducing a wider luminance range and often a wider colour volume. HDR requires a defined transfer/rendering context, not merely a brighter monitor.

Full chapter

HDR and displays

Nit / cd/m²

A unit of luminance: 1 nit equals 1 candela per square metre. Used for display luminance, reference white and mastering/display peaks.

Full chapter

HDR and displays

PQ / ST 2084

Perceptual Quantizer — an absolute HDR EOTF mapping signal values to defined display luminance values up to a mathematical ceiling of 10,000 cd/m².

Full chapter

HDR and displays

HLG

Hybrid Log-Gamma

A relative HDR signal system combining a square-root lower region with a logarithmic upper region; final display behaviour includes a system gamma.

Full chapter

HDR and displays

HDR reference white

A working reference luminance for diffuse/graphics white in HDR production. ITU BT.2408 commonly uses a nominal HDR reference white around 203 cd/m².

Full chapter

HDR and displays

Mastering display

The reference display on which a master is evaluated and approved; its black, peak and gamut capabilities are part of the mastering context.

Full chapter

HDR and displays

MaxCLL

Maximum Content Light Level

A static HDR metadata field describing the maximum content light level in a master under the defined measurement. It is not the display peak.

Full chapter

HDR and displays

MaxFALL

Maximum Frame-Average Light Level

A static HDR metadata field describing the highest frame-average luminance across the programme; it differs from MaxCLL.

Full chapter

HDR and displays

Colour volume

The three-dimensional region of available colours including chromaticity and luminance. A 2D gamut triangle alone does not fully describe an HDR display.

Full chapter

Pipeline and Resolve

Input Transform

A technical transform that maps a known source state into a chosen working/common representation. Incorrect source interpretation breaks the rest of the chain.

Full chapter

Pipeline and Resolve

Output Transform

A transform/rendering stage that maps the working/scene state to a target display/output state. It can include tone/gamut rendering, not only matrix + gamma.

Full chapter

Pipeline and Resolve

CST

Color Space Transform

Resolve OFX for explicit Input Colour Space/Gamma → Output Colour Space/Gamma conversion with optional tone/gamut mapping controls.

Full chapter

Pipeline and Resolve

RCM

Resolve Color Management

DaVinci Resolve's project-level managed colour pipeline: source tagging/input transforms, timeline working state and output rendering are managed by the project system.

Full chapter

Pipeline and Resolve

LUT

Look-Up Table

A tabulated mapping from input values to output values. A LUT can be technical or creative but always assumes a specific input/output state and does not infer context automatically.

Full chapter

Pipeline and Resolve

ACES

Academy Color Encoding System

A standardised colour-management and interchange architecture from the Academy using common scene-referred representations and defined Input/Look/Output transforms.

Full chapter

Pipeline and Resolve

AP0

The very wide ACES primary set used by the ACES2065-1 archival/interchange representation.

Full chapter

Pipeline and Resolve

AP1

A more compact ACES primary set used by working encodings including ACEScg and ACEScct.

Full chapter

Pipeline and Resolve

ACEScct

An AP1-based scene-referred ACES grading encoding with a toe near black, designed for colour grading.

Full chapter

Pipeline and Resolve

DaVinci Wide Gamut

DWG

Blackmagic Design's wide RGB working gamut for Resolve, commonly paired with DaVinci Intermediate in scene-referred RCM/CST workflows.

Full chapter

Pipeline and Resolve

DaVinci Intermediate

Blackmagic Design's log-like scene-referred transfer function intended to pair with DaVinci Wide Gamut as a wide working state.

Full chapter

Pipeline and Resolve

Colour Management

A system for explicitly tracking source, working and output states and the transforms between them so numeric values are interpreted consistently throughout the chain.

Full chapter

Pipeline and Resolve

Display calibration

Measurement and adjustment of a monitor response to a defined target: white point, luminance, transfer, gamut and, where applicable, uniformity/black. A viewer transform does not replace physical display calibration.

Full chapter

Pipeline and Resolve

Reference monitoring

A controlled display path with a known output transform, signal path and calibrated reference display on which colour decisions are made.

Full chapter

How to use the glossary

Find the term through search and read the short operational definition first. If it affects a real transform, monitoring or delivery decision, continue to the linked full chapter. This keeps the glossary fast without reducing complex concepts to dangerous one-line rules.

Similar words can belong to different layers

Colour pipelines contain physical light, perceptual attributes, colorimetric coordinates, RGB encodings, component-video representation and display rendering. Luminance is a photometric quantity, Y′ luma is a video-signal component and Lightness is a perceptual attribute. They are related but not interchangeable.

Terms that are especially dangerous to treat as synonyms

Gamut is not the same as colour space; log is not RAW; HDR is not Rec.2020; bit depth is not dynamic range; 4:2:2 says nothing about bit depth; a metadata tag does not perform a transform; scene-referred is not necessarily linear; Y′CbCr is not a separate gamut. Many practical errors begin with these substitutions.

A signal has a grammar: describe its state with independent properties

Instead of saying only 'this is Rec.709', think in a tuple: primaries/gamut + transfer + matrix representation + range + bit depth + chroma sampling + metadata/container assumptions. Camera sources add camera gamut/log or RAW decode state; working pipelines add a working gamut/transfer; output adds target display/rendering.

Primes and units are not typography

R′G′B′ and Y′ denote nonlinear signal-domain quantities, while unprimed RGB may be used for linear-light contexts. cd/m² (nit) is display luminance, a code value is a number in an encoding and a stop is a logarithmic exposure/light ratio. Mixing these notations can make a formula mathematically neat but conceptually wrong.

How to translate Resolve UI labels into colour-science language

Input Colour Space/Gamma defines source interpretation for a transform; Timeline Colour Space describes the working context in a managed workflow; Output Colour Space defines the target output state; CST explicitly connects two known states; Data Levels concerns range interpretation; RAW controls occur before the ordinary node tree. A dropdown name is only a label for a specific place in the pipeline.

What this changes in post

If you cannot define a term in one sentence and name the layer of the chain where it acts, do not change the setting by guesswork; open the linked chapter first.

Common mistakes

Treating everyday and technical definitions as identical.

Mixing perceptual, colorimetric and signal-domain quantities.

Memorising an acronym without its input/output context.

Treating a UI label as a complete file specification.

Standards and primary references

Technical definitions are anchored to standards bodies and primary specifications wherever that distinction matters.

CIE e-ILV — International Lighting Vocabulary

Official open vocabulary for terms from CIE S 017:2020.

ITU-T H.273 — Video signal type identification

Colour primaries, transfer characteristics, matrix coefficients, range and chroma sample location signalling.

ACES — Glossary