Overview
EN ISO/CIE 11664-1:2019 - "Colorimetry - Part 1: CIE standard colorimetric observers" defines the colour‑matching functions used as the basis for modern colorimetry. Published in 2019 (CEN/CIE), this standard specifies two sets of CIE standard colorimetric observers and the conditions under which each set applies. It is the reference for converting spectral data into tristimulus values used in color measurement, specification and comparison.
Key topics and requirements
- Two standard observers
- CIE 1931 standard colorimetric observer: representative for observers with normal colour vision for visual fields of about 1°–4° angular subtense under photopic (daylight) adaptation.
- CIE 1964 standard colorimetric observer: representative for larger fields (greater than 4°) under sufficiently high photopic levels and where rod receptor participation is negligible.
- Colour‑matching functions: prescriptive spectral functions used to compute XYZ tristimulus values from spectral stimulus functions.
- Spectral chromaticity coordinates: definitions and normative reference data for spectral loci.
- Derivation and transformation: documented experimental basis, transformation procedures and properties used to derive the standard functions and to compare them with earlier data.
- Practical application guidance: procedures for obtaining tristimulus values, numerical integration basis, treatment of rod activity, use of restricted data and standards of reflectance.
- Normative references: includes relevant CIE/ISO lighting vocabulary and related colorimetry parts.
Applications and users
EN ISO/CIE 11664-1:2019 is essential for anyone involved in quantitative colour work who requires consistent, comparable results:
- Color scientists and researchers implementing colorimetric calculations.
- Lighting and display engineers converting spectral power distributions to colour coordinates.
- Instrument manufacturers for spectrophotometers and colorimeters to ensure device calibration and reporting conform to standard observers.
- Paints, coatings, textiles and printing professionals specifying and matching colours across suppliers and regions.
- Standards bodies and laboratories performing color measurement, quality control and conformity testing.
Using the standard ensures that spectral measurements translate to perceptually meaningful tristimulus values and that metameric matches are evaluated consistently across applications.
Related standards
- ISO/CIE 11664 series (other parts cover color difference formulas, observers, illuminants, etc.)
- CIE S 017 (International Lighting Vocabulary) - normative terminology used in the document
Keywords: colorimetry, CIE standard colorimetric observers, colour‑matching functions, CIE 1931, CIE 1964, tristimulus values, photopic, standard observer.