CIE S 026'E-2018 PDF

Full title and description

CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light (CIE S 026/E:2018). This International Standard defines spectral sensitivity functions, a-opic quantities and metrics to describe how optical radiation stimulates the five retinal photoreceptor types (L-, M-, S-cones, rods and melanopsin-containing intrinsically photosensitive retinal ganglion cells — ipRGCs) that can contribute to retina-mediated non-visual (ipRGC-influenced) responses to light.

Abstract

The standard establishes a metrology system for characterizing visible optical radiation (380–780 nm) with respect to its ability to stimulate each of the five photoreceptor classes relevant to non-image-forming (NIF) responses. It defines spectral sensitivity (action) functions, a-opic quantities (for example melanopic equivalent daylight illuminance and melanopic efficacy ratio), recommendations for age and field-of-view corrections, and provides machine-readable tables of the action spectra for use in calculations. The document is explicit that it does not provide complete application-specific dose–response predictions and is not intended for colorimetric contexts or to address clinical/photobiological safety protocols.

General information

• Status: International Standard (published by the Commission Internationale de l’Éclairage / CIE; current publication: CIE S 026/E:2018).
• Publication date: 2018 (published December 2018 — edition referenced as 2018).
• Publisher: CIE Central Bureau (Commission Internationale de l’Éclairage).
• ICS / categories: Listed under optoelectronics / optical radiation standards (examples of catalogue entries cite ICS 31.260 — optoelectronics).
• Edition / version: CIE S 026/E:2018 (first published edition, 2018).
• Number of pages: 36 pages (standard publication).

Scope

The standard applies to visible optical radiation from 380 nm to 780 nm and defines the spectral sensitivity functions, quantities and metrics needed to quantify stimulation of retinal photoreceptors that may contribute to ipRGC-influenced (retina-mediated non-visual) responses. It includes guidance on age- and field-of-view–dependent corrections and supplies the action spectra data in downloadable form for calculations, but it does not attempt to provide application-specific exposure limits, clinical prescriptions, or address non-retinal effects, flicker, or photobiological safety.

Key topics and requirements

• Definition of five a-opic spectral sensitivity (action) functions: L-cone-opic, M-cone-opic, S-cone-opic, rhodopic (rod) and melanopic (ipRGC/melanopsin).
• Formal a-opic quantities and metrics (examples include melanopic equivalent daylight (D65) illuminance — mEDI — and melanopic daylight efficacy ratio — mDER) and the equations needed to compute them from spectral power distributions.
• Wavelength applicability: 380–780 nm (visible spectrum).
• Age and field-of-view (FOV) correction guidance to account for lens transmission and effective retinal illumination differences across user populations.
• Provision of electronic tables of the action spectra and a recommended toolbox/user guide (α‑opic Toolbox) to support implementation and conversions; toolbox released by CIE as a companion resource (not a replacement for the standard).
• Statements clarifying limits: not intended for colorimetry contexts or to provide clinical/photobiological safety advice or exposure prescriptions.

Typical use and users

Intended users include lighting researchers and metrologists, lighting and display designers and manufacturers, architects and building designers interested in human-centric lighting, occupational health professionals, standards developers, and academic researchers studying circadian and non-visual responses to light. The CIE has developed a tutorial and supporting materials (Toolbox and User Guide) to aid adoption by these audiences.

Related standards

Complementary and related documents include CIE technical publications on ocular transmission and photometry (for example CIE 203 on ocular transmission), other CIE/ISO colorimetry and lighting standards that cover visual aspects and measurement practice, regional standards and technical specifications that harmonize with CIE S 026 (examples: national and DIN/CEN documents aligning melanopic metrics to local practice). The CIE α‑opic Toolbox and User Guide are companion resources to support implementation.

Keywords

ipRGC, melanopsin, melanopic, a-opic, non-visual, circadian, mEDI, mDER, spectral sensitivity, photoreceptor action spectra, metrology, a‑opic Toolbox.

FAQ

Q: What is this standard?

A: An international CIE standard that defines how to measure and express the capacity of visible light (380–780 nm) to stimulate each of the five retinal photoreceptor types that can contribute to ipRGC‑influenced (non-visual) responses; it provides spectral sensitivity functions, quantities and calculation methods.

Q: What does it cover?

A: It covers definitions of a-opic action spectra, formal a-opic quantities (e.g., melanopic equivalent daylight illuminance and related metrics), calculation procedures, and guidance on age and field-of-view effects. It also supplies electronic action‑spectrum tables for users. It does not provide exposure limits, clinical treatment guidance, or address photobiological safety/flicker issues.

Q: Who typically uses it?

A: Lighting researchers, metrologists, lighting and display manufacturers, architects and building designers, occupational and environmental health professionals, and standards organizations — essentially anyone needing a standardized, reproducible method for quantifying the non-visual (ipRGC-influenced) stimulus from light. The CIE has provided tutorials and a Toolbox to support these user groups.

Q: Is it current or superseded?

A: CIE S 026/E:2018 is the published CIE international standard (2018 edition) for this metrology; companion implementation materials (α‑opic Toolbox and User Guide) were released subsequently to support use. No later CIE standard has officially superseded S 026 as of the publication of the CIE catalogue entries and companion materials. Users should check the CIE publications catalogue or national committee announcements for any subsequent revisions.

Q: Is it part of a series?

A: It is a CIE International Standard prepared by a joint technical committee and reported under the CIE divisions concerned with vision, physical measurement and photobiology; it is part of the body of CIE standards and technical reports addressing measurement and human responses to light and is supported by companion CIE reports and tools.

Q: What are the key keywords?

A: ipRGC, melanopic, a-opic, non-visual effects, spectral sensitivity, circadian stimulus, mEDI, mDER, metrology.