Overview
EN ISO 18314-3:2022 - Analytical colorimetry - Part 3: Special indices defines standardized methods for calculating one-dimensional colour indices used to describe lightness/jetness, chroma and hue contributions within a single colour coordinate. The standard applies to tristimulus values and chromaticity coordinates computed with the CIE 1931 (2°) or CIE 1964 (10°) colour-matching functions and is intended for colour stimuli perceived as belonging to reflecting or transmitting objects where a single index is required.
Key topics and technical requirements
- Scope & applicability
- Indices are applicable to measurements based on standard observers (2°/10°) and standard illuminant D65 where relevant.
- Specified indices and formulas
- CIE whiteness index (W) - formula and recommended parameter values for D65/2° and D65/10°.
- Yellowness index (YI) - formula with coefficients (a, b) for 2° and 10° observers (aligns with ASTM E313–20 and DIN 6167).
- Blackness (M) and greyness (G) values - both hue-independent and hue-dependent forms, including absolute hue contribution terms (dM, dG). Hue-dependent forms account for blue/brown shifts.
- Flop-index (FI) - a measure of angular lightness variation for near-neutral metallic shades using CIELAB L*(ε) at specified aspecular angles.
- Measurement considerations
- Indices are calculated from tristimulus (X, Y, Z) and chromaticity (x, y) data.
- Annex A discusses metrological considerations for low-radiance (jetness) measurement, recommending instrument geometries (e.g., 45°:0° spectrophotometry) and reproducibility targets for Y.
- Normative references
- Cross-references to ISO 18451-1 (terminology) and recognition of related documents (CIE, ASTM, DIN).
Applications and users
- Who uses it
- Pigment, dye and extender manufacturers; paint, coatings and plastics producers; textile and printing quality labs; colour measurement labs; research groups and standards bodies.
- Practical uses
- Quality control and specification of whiteness, yellowness, jetness/blackness and grey balance.
- Comparative evaluation of metallic effect pigments (flop-index) and angular lightness behavior.
- Converting spectral or tristimulus measurements into single-value indices for specification sheets, tolerancing and supplier contracts.
Related standards
- ISO 18314 series (analytical colorimetry)
- ISO 18451-1 (terminology)
- CIE standards (CIE 1931, CIE 1964, CIE whiteness guidance)
- ASTM E313–20 (yellowness index methods)
- Relevant national standards cited (e.g., DIN 55979, DIN 6167)
Keywords: EN ISO 18314-3:2022, Analytical colorimetry, special indices, tristimulus values, chromaticity coordinates, CIE 1931, CIE 1964, whiteness index, yellowness index, blackness value, greyness value, flop-index, pigment quality control.
