Overview
ISO/CIE 11664-1:2019 - Colorimetry Part 1: CIE standard colorimetric observers specifies the colour‑matching functions used in modern colorimetry. It defines two standard observer models:
- CIE 1931 standard colorimetric observer - representative for centrally viewed fields of angular subtense about 1° to 4°, at photopic adaptation levels.
- CIE 1964 standard colorimetric observer - representative for larger fields (>4°) under sufficiently high photopic conditions where rod participation is negligible.
The standard provides formal definitions, spectral chromaticity coordinates, and the reference functions required to compute tristimulus values and chromaticity from spectral data.
Key topics
- Colour‑matching functions: Precise sets for the 1931 (2°/~1–4° field) and 1964 (10°/>4° field) observers used to convert spectral distributions to tristimulus values (X, Y, Z).
- Spectral chromaticity coordinates: Definitions and tabulated spectral x(λ), y(λ), z(λ) (and 10° equivalents) for monochromatic stimuli.
- Derivation and transformation: Experimental basis, transformation procedures and properties used to derive the standard functions and to compare them with earlier data.
- Tristimulus calculation: Requirements and guidance for obtaining tristimulus values from spectral stimulus functions, including the numerical basis for spectral integration.
- Practical considerations: Rod activity/photopic limits, use of restricted data sets, and the standard of reflectance to ensure consistent, reproducible colorimetric measurements.
- Terminology and normative references: Uses CIE/ISO terms (e.g., metamerism, tristimulus, spectral luminous efficiency); refers to CIE S 017 and related colorimetry guidance.
Applications
ISO/CIE 11664-1:2019 is essential for any activity that converts spectral power distributions into perceptual color coordinates:
- Color specification and communication across industries (paints, textiles, printing).
- Colour quality and consistency in display, lighting and imaging systems.
- Color measurement instrument design, calibration and validation (spectroradiometers, colorimeters).
- Metamerism assessment, colour matching and colour tolerance evaluation in quality control labs.
- Research in vision science and colour appearance where standard observer models are required.
Who uses this standard
- Colour scientists and vision researchers
- Lighting and display manufacturers
- Color measurement instrument designers and calibration labs
- Quality assurance and production engineers in materials and printing
- Standards bodies and test laboratories implementing colorimetric methods
Related standards
- CIE 15: Colorimetry (detailed procedures and broader framework)
- CIE S 017: International Lighting Vocabulary (terminology)
- Other parts of ISO/IEC 11664 series covering illuminants, colour difference, colorimetry procedures
ISO/CIE 11664-1:2019 is the foundational reference for converting spectral data into standardized colorimetric values using the CIE 1931 and 1964 observer functions - a core requirement for reproducible, interoperable colour measurement and communication.