Overview - ISO/CIE 11664-6:2022 (CIEDE2000 colour‑difference formula)
ISO/CIE 11664-6:2022 specifies the method for computing perceptual colour differences using the CIEDE2000 (ΔE00) colour‑difference formula. It applies to CIELAB L*, a*, b* coordinates calculated per ISO/CIE 11664‑4 (CIE 1976 Lab*). The standard defines reference viewing conditions, limitations on applicability (for reflecting or transmitting objects and properly normalized display simulations) and parameter options to correct for deviations from reference conditions.
Key topics and technical requirements
- Input space: Requires CIELAB L*, a*, b* coordinates computed according to ISO/CIE 11664‑4.
- Formula: Defines the CIEDE2000 calculation (ΔE00) with corrections for lightness, chroma, hue, chroma–hue interaction, weighting functions, rotation term and a T-function for hue weighting.
- Parametric factors: kL, kC, kH allow adjustment for non‑reference experimental or material conditions; default value is 1 under reference conditions. (Note: textile practice sometimes uses kL = 2.)
- Reference conditions (intended application):
- Illumination: CIE standard illuminant D65 spectral simulation
- Illuminance: 1 000 lx
- Observer: normal colour vision
- Background: uniform neutral grey L* = 50
- Viewing mode: object (sample pair subtending > 4° visual angle)
- Sample separation: direct edge contact
- Typical colour‑difference magnitude: 0–5 CIELAB units
- Sample structure: homogeneous colour without visible pattern
- Limitations: Not intended for stimuli perceived as emitting light (primary light sources) or for areas specularly reflecting such light. Displays may be used only when tristimulus values are appropriately normalized to simulate reflecting/transmitting objects.
- Informative annex: Annex A describes a three‑component micro‑space formulation for apportioning differences into lightness, chroma and hue components.
Applications and who uses it
- Quality control and tolerance specification in paint, coatings, textiles, plastics, printing and automotive colour matching.
- Colour management and imaging workflows where accurate perceptual ΔE evaluation is required.
- Display and simulation testing when displays are used to represent reflective/transmissive objects (with normalized tristimulus data).
- Researchers and colour scientists implementing colour‑difference metrics and comparing algorithm performance.
Users include colour technologists, QC engineers, product designers, colorimetry software developers and standards bodies.
Related standards and references
- ISO/CIE 11664‑4 - Colorimetry: CIE 1976 Lab* colour space (required input coordinates)
- CIE 142:2001 - Basis for CIEDE2000 development
- CIE 230:2019 - Notes on validity for small colour differences
- Implementation notes and worked examples referenced in the CIE literature (e.g., Sharma et al.)
Keywords: ISO/CIE 11664‑6:2022, CIEDE2000, ΔE00, colour difference, CIELAB, colorimetry, colour tolerance, colour measurement, color management.