ISO/CIE 23539:2023 PDF

Overview

ISO/CIE 23539:2023 - Photometry - The CIE system of physical photometry - specifies the internationally agreed system for measuring light as perceived by humans. Published jointly by ISO and the CIE and accepted by the CIPM, this standard defines the photometric quantities, units and spectral luminous efficiency functions used to convert radiometric measurements into photometric values referenced to the SI base unit, the candela. It updates and consolidates CIE reference functions for photopic, scotopic, mesopic and 10° photopic vision and sets out maximum luminous efficacy values and measurement guidance.

Key topics and requirements

• Definition of photometric quantities, symbols and units aligned with the SI (including the candela reformulation).
• CIE spectral luminous efficiency functions for:
  • Photopic vision (V(λ))
  • Scotopic vision (V′(λ))
  • Mesopic vision (Vmes(λ)) and associated guidance
  • 10° photopic vision (V10(λ))
• CIE photometric observers: standardized relative spectral responsivities that represent human visual response under different adaptation conditions.
• Maximum luminous efficacy values for photopic, scotopic, mesopic and 10° photopic observers.
• Formulae linking radiometric and photometric quantities, including luminous flux and luminous efficacy calculations.
• Physical measurement guidance: recommendations for using photometers and spectroradiometers, spectral measurements, tabulated values, and interpolation rules.
• Normative references and tables of tabulated spectral luminous efficiency values and informative annexes on background, mesopic examples and cone-fundamental functions.

Applications and users

ISO/CIE 23539:2023 is essential for professionals involved in objective measurement, specification and regulation of lighting:

• Lighting manufacturers (luminaire, lamp and LED producers) for product specification and photometric data.
• Test laboratories and accredited calibration labs for traceable photometric measurements.
• Lighting designers and engineers who perform lighting calculations and ensure compliance with performance criteria.
• Metrologists and standards organizations implementing SI-consistent photometry.
• Researchers in vision science, night-time lighting, roadway lighting and spectral lighting effects (mesopic conditions).

Practical uses include calculating luminance, luminous flux and luminous efficacy from spectral data, comparing light sources regardless of spectral composition, and establishing calibration procedures for photometers and spectroradiometers.

Related standards

• CIE S 017 (International Lighting Vocabulary) - terminology.
• CIE 018:2019 - source of mesopic and 10° photopic functions referenced in this edition.
• CIE 170-2:2015 - cone-fundamental-based functions (referenced in annexes).
• CIE S 026/E:2018 - non-image-forming (ipRGC) effects (contextual reference).

ISO/CIE 23539:2023 provides the authoritative, SI-linked framework for accurate, reproducible human-centric photometric measurement and reporting.