BIPM and CIE Renew Agreement to Strengthen Optical Measurement Standards
A newly signed Memorandum of Understanding (MoU) between the BIPM and the International Commission on Illumination (CIE) reinforces their joint commitment to advancing global comparability in optical measurements, including photometry, radiometry and digital metrology.
The agreement was signed on 15 July 2025 in Varenna, Italy, by Martin Milton, Director of the BIPM and Diana Wernisch, Secretary General of the CIE. The MoU updates and replaces the previous agreement signed in 2007.
It formalizes collaboration in several key areas:
- ensuring data related to measurements of light, optical radiation, colour, optical properties of materials, photobiological and photochemical quantities are properly based on units traceable to the International System of Units (SI) and internationally recognized through the CIPM MRA,
- ensuring the definition of photometric units based on the constant for the luminous efficacy of defined visible radiation, Kcd, remains fit for purpose,
- collaborating on the development, implementation and promotion of the SI Digital Framework.
This renewed partnership reflects the BIPM’s broader mission to strengthen international measurement systems and support scientific and technological progress across sectors.
Background
The BIPM and CIE have enjoyed an excellent and longstanding collaboration through their work with the Consultative Committee for Photometry and Radiometry (CCPR), established in 1933, and the Consultative Committee for Units (CCU), set up in 1964.
In 2007, this cooperation was further formalized when the CIE and CIPM signed their first agreement, marking nearly two decades of structured partnership in maintaining consistency in optical measurement science.
The BIPM, through the CIPM and its Consultative Committees, sustains global coherence in SI units, while the CIE brings essential expertise in defining photobiological and photochemical quantities, including standardized action spectra.
Their combined efforts ensure that measurements of light and radiation remain accurate, traceable and universally comparable.