Figure 1

The light spectra of the bright and dim light conditions, showing spectral radiances normalized to the emission peak. The LEDs had a strong emission peak in the blue spectrum near 450 nm (typical for GaN based LEDs) and a broadband emission centred at a wavelength of 560 nm (yellow-green spectrum; originating from the phosphor layer). In the dim light condition, the spectrum altered in the way that the ratio of the blue peak and the broadband peak changed. At bright light conditions (black solid line), the fraction of blue emission (and therefore the colour temperature) was higher than when dimmed (red dashed line). This mimics the change from a mid-day light spectrum to an evening spectrum. The light spectrum for the dimmed treatment was closer to real-world street lighting or skyglow from LEDs.