Photoreceptor-specific scene statistics reveal melanopic structure in natural environments

Natural scenes shape both visual perception and non-visual light responses, but the melanopsin pathway, the retina’s key circadian input, has rarely been quantified in this context. We measured the spectral and spatial properties in 675 natural scenes, including indoor without windows (n=115), indoor with windows (n=194), and outdoor (n=366), quantifying input across all five human photoreceptors. Radiance and photometric metrics increased systematically across scene types from indoor without window view (mean melanopic EDI 280 lx), indoor with window view (mean melanopic EDI 2386 lx) to outdoors (mean melanopic EDI 12,142 lx), with melanopic and photopic illuminance strongly correlated ( r ≈ 0.9, p < 10 ⁻⁵ ). RMS contrast ranged from 0.001 to 0.365, lowest indoors without windows and highest outdoors, with melanopic luminance associated with contrast indoors with windows ( r = 0.48) and outdoors ( r = 0.49) but not windowless ( r = 0.03). Amplitude spectra followed power laws (−0.9 to −1.9), steeper indoors (−1.4) and flatter outdoors (−1.1). These results reveal systematic, context-dependent melanopsin scene statistics, extending natural scene analysis beyond cone pathways.