Tony Esposito and Kevin Houser published a new study in Scientific Reports demonstrating that CCT is not suitable for predicting the biological potency of light. The experiments utilized a 5-channel LED lighting system to show that significant variation in CS and EML/mEDI exists at any fixed value of CCT and photopic illuminance.
For many years, some lighting manufacturers have been switching between high and low CCTs and claiming circadian benefit. While such benefit is possible, this research
spells out clearly that you can’t count on CCT being a proxy for useful circadian stimulus. The researchers demonstrate that you can have high CCT without having high circadian effect under both the CS and EML/mEDI theories. Same with low CCT / low circadian effect.
Excerpt from the study’s conclusions:
“….we need accurate and predictive measures of the biological potency of light that are based on sound science. In this study, we have argued that CCT is conceptually inappropriate for this purpose and performed a numerical analysis demonstrating that significant variation in circadian stimulus and melanopic equivalent daylight illuminance exists at any fixed CCT and photopic illuminance, making CCT an inappropriate proxy of those measures. Using CCT as a proxy for the biological potency of light cannot be justified.”
The full study can be found here.