Figure 8
From: Correlated color temperature is not a suitable proxy for the biological potency of light
Circadian stimulus (CS) as a function of nominal CCT at a photopic illuminance of 300 lx. (Top left) All SPDs for the “Filtered” dataset. (Top right) The “Filtered” dataset further filtered for Rf ≥ 70. (Bottom left) The “Filtered” dataset further filtered for Rf ≥ 80. (Bottom right) The “Filtered” dataset further filtered for Rf ≥ 90. “rBY-” indicates the “yellow wins” scenario of the CS model (also indicated by the horizontal hatching and circle markers); “rBY+ ” indicates the “blue wins” scenario of the CS model (also indicated by the vertical hatching and square markers). Lines show the maximum (grey), minimum (grey), and average (black) CS within each nominal CCT; error bars indicate the standard deviation. On average, sources with rBY- have higher CS values than sources with rBY+. The b-y spectral opponency causes the observable discontinuity near 3500 K where the model switches from one hypothetical model of phototransduction to another. As the average fidelity floor is raised (i.e., from Rf ≥ 70 to Rf ≥ 80 to Rf ≥ 90), the achievable CS range decreases.
