ISO/CIE 11664-2:2022 PDF

Overview

ISO/CIE 11664-2:2022 - Colorimetry - Part 2: CIE standard illuminants defines three CIE standard illuminants used in colorimetry: Illuminant A (typical tungsten‑filament lighting), D65 (average daylight, nominal correlated colour temperature ≈ 6500 K), and D50 (daylight, nominal correlated colour temperature ≈ 5000 K). The standard provides the relative spectral power distributions (SPDs) of these illuminants at 1‑nm intervals from 300 nm to 830 nm, and gives the mathematical definition of Illuminant A (normalized to 100 at 560 nm). These illuminants are defined spectral references - not necessarily realizable light sources - used to compute colourimetric quantities such as tristimulus values.

Key topics and requirements

• Defined illuminants: CIE standard illuminant A, D65 and D50 with explicit SPDs (see Annex A for A and Annex B for D65/D50).
• Spectral sampling: SPD values are tabulated at 1‑nm intervals (300–830 nm); linear interpolation is permitted for intermediate values.
• Illuminant A formula: Analytical definition based on a Planckian radiator (assigned temperature ≈ 2855.5 K) and normalized at 560 nm.
• Correlated colour temperature (CCT): Nominal CCTs are given (D65 ≈ 6500 K; D50 ≈ 5000 K) with notes on evaluated CCT using specific constants.
• Practical source guidance: CIE standard source A (practical realization of illuminant A) is described; no CIE‑recommended physical sources are currently specified for D65 and D50.
• Usage guidance: Illuminants are recommended for colorimetric calculations unless specific reasons require a different illuminant; variations in real daylight (especially UV) are noted.

Applications and who uses it

• Color scientists and metrologists use these standard illuminants for accurate colorimetry, spectral measurements and device calibration.
• Imaging, photography and graphic arts professionals rely on D50/D65 for standard viewing/soft proofing and color matching workflows.
• Printing, paint, textiles and coatings industries apply these illuminants for product specification, quality control and colour tolerancing.
• Display and lighting manufacturers use the SPDs for color performance characterization and calibration.
• Laboratories and standards bodies use the tabulated SPDs to compute tristimulus values, create test patterns and compare published results consistently.

Related standards

• CIE 015 (procedures and other illuminants)
• CIE S 017 (vocabulary/definitions)
• CIE 018 (standard air definition)
• ISO/CIE 11664 series (other parts of the colorimetry standard)

Keywords: ISO/CIE 11664-2:2022, CIE standard illuminants, D65, D50, Illuminant A, colorimetry, spectral power distribution, correlated colour temperature, color calibration.