Two of the SSLC Platform Experts, working with an independent researcher, have published a paper that updates and improves a flicker metric first introduced in 2015. Our experts, Dr. Jiaye (Jane) Li and Dr. Yoshi Ohno, co-authored a paper with Andrew Bierman from Albany, New York (USA), titled “Revision of M_P calculation method for flicker measurement,” published today in Lighting Research & Technology.

This work originated from findings during the SSLC Platform’s Interlaboratory Comparison 2023 (IC 2023), where large variations in measured M_P metric values were observed among laboratories. The authors identified that these variations were primarily caused by limitations in the original M_P calculation method, leading to significant measurement uncertainty. The revised calculation method presented in the paper substantially reduces these uncertainties and improves the consistency and robustness of flicker measurements.

This publication is an excellent example of how the IEA 4E SSLC Platform contributes to advances in lighting science and measurement practices. Through collaborative international work, the Platform helps identify technical challenges, improve lighting metrics, and support policymakers in protecting human health.

Below are the citation and link to the open-access paper, together with the abstract.

Li J., Bierman A., Ohno Y.; Revision of M_P calculation method for flicker measurement. Lighting Research & Technology. 2026;0(0). doi: 10.1177/14771535261435634

Direct flicker is a perception effect causing discomfort generated from lighting systems. While the short-term flicker indicator, P_st^LM, most widely used, perceptual modulation (M_P) is also a perception-based direct flicker metric used in many commercial instruments. However, M_P values show substantial variation due to different starting phases of waveforms, caused by Fourier transform spectral leakage. Such variation was mostly removed by revising M_P’s calculation, applying a Hann window function and a correction factor to counteract the spectral broadening from the window when summing the DC-normalized spectral components. This approach is generalized to improve frequency-domain temporal light artefact metrics without loss of perceptual relevance when different windows are applied. To harmonize M_P with direct flicker at a broader frequency range and viewing conditions eliciting higher direct flicker sensitivity, its original sensitivity curve (5 Hz to 65 Hz) is replaced by the one from Perz’s experiment, with a slight change of frequency range to 3 Hz to 80 Hz. With these improvements, M_P,26 has been developed. A linear mixed-effects model is used to compare the different measurement conditions of M_P,26, providing guidance for recommended measurement conditions, i.e. measurement duration ≥5 s, sampling rate ≥2 kHz and a second-order anti-aliasing filter with cut-off frequency ≥400 Hz are recommended for robust result of M_P,26.