Scope
Names, symbols, definitions, and units for quantities of light and optical radiation in the wavelength range of approximately 1 nm to 1 mm — bridging radiometric, photometric, and photon-based measurements.
What You'll Find
Distinguishes three categories of quantities: radiometric (all EM radiation), photometric (visible light, weighted by human vision), and photon (particle count based)
Uses subscript conventions: "e" for energetic/radiometric, "v" for visible/photometric, "p" for photon quantities
Covers spectral quantities — derivatives with respect to wavelength, frequency, or wavenumber — and their mathematical interrelations
Explains the three visual regimes: photopic (daylight), scotopic (night), and mesopic (intermediate), each with different luminous efficiency functions
Retains the steradian in photometry and radiometry for practical convenience
Cross-references Part 10 for ionizing radiation quantities. The spectral luminous efficacy values are based on CIE standards from 1924 (photopic) and 1951 (scotopic).
Obtain the Standard
Published by the International Organization for Standardization (ISO). Edition 2019 (2nd). Developed by ISO/TC 12 — Quantities and units.
Browse Entries
66 quantities defined in Part 7