Nominal CCT is an insufficient predictor of melanopic efficacy: statistical evidence from measured neutral-white LED light sources

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DOI:

https://doi.org/10.4302/plp.v18i2.1397

Abstract

Nominal Correlated Color Temperature (CCT) is widely used to specify neutral‑white LED luminaires, yet it is insensitive to the melanopic pathway governing circadian entrainment. This study statistically characterises the melanopic Daylight Efficacy Ratio (m‑DER, CIE S026/E:2018) across 279 measured 4000 K commercial LED spectra from the EMPIR/PNNL databases. The m‑DER distribution is non‑normal and wide (0.419–0.722; SD = 0.051); CCT explains only 16 % of within‑class variance (Pearson r = 0.395, r² ≈ 0.156; Spearman ρ = 0.470). Seven percent of products fail the CIE PS001:2024 daytime threshold (m‑EDI ≥ 250 lx at E = 500 lx).
A novel asymmetry is identified: the Duv‑m‑DER correlation is significant above the Planckian locus (ρ = −0.333) but negligible below it (ρ = 0.071, p = 0.477). These findings strongly support m‑DER disclosure as a necessary step toward reliable human-centric lighting specification.

 

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References

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Published

2026-07-01

How to Cite

[1]
M. Listowski, P. Bałdyga, B. Gajewski, and I. Fryc, “Nominal CCT is an insufficient predictor of melanopic efficacy: statistical evidence from measured neutral-white LED light sources”, Photonics Lett. Pol., vol. 18, no. 2, pp. 23–25, Jul. 2026.

Issue

Vol. 18 No. 2 (2026)

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Articles

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Copyright (c) 2026 Maciej Listowski, Piotr Bałdyga, Błażej Gajewski, Irena Fryc

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