Fig. 3

A direct comparison of the levels and spectra of light measured indoors and outdoors. A Light levels outdoors are significantly higher than light levels indoors. B The light spectrum outdoors remains fairly unaltered when measured in different locations. Conversely, light levels outdoors can decrease by ~1 log unit between an open field and a denser building area or even indoors looking out from a window. Conversely, light levels can drop by more than 10 log units in a room equipped with artificial lighting. C The spectral power distribution of the average measurements outdoors (±SEM) compared to indoor scenarios. D, E, and F Normalized spectral power distribution of light outdoors compared to light indoors. While the spectrum remains fairly similar between 400 and 650 nm, windows block a considerable amount of ultra-violet (<400 nm) and near-infrared or infrared light (>650 nm) (D). Similar differences are observed between traditional indoor LED lighting (CCT: 4000 K) in addition to reduced composition in wavelengths between 400–440 nm and 480–560 nm (E). Similar observations can be made when comparing artificial lighting to sunlight seen through a window (F)