December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Spatial and temporal dynamics of effective daylight in natural scenes
Author Affiliations & Notes
  • Cehao Yu
    Perceptual Intelligence Lab (π–Lab), Delft University of Technology
  • Maarten Wijntjes
    Perceptual Intelligence Lab (π–Lab), Delft University of Technology
  • Elmar Eisemann
    Computer Graphics and Visualization Group, Delft University of Technology
  • Sylvia Pont
    Perceptual Intelligence Lab (π–Lab), Delft University of Technology
  • Footnotes
    Acknowledgements  This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 765121; project "DyViTo".
Journal of Vision December 2022, Vol.22, 3984. doi:
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      Cehao Yu, Maarten Wijntjes, Elmar Eisemann, Sylvia Pont; Spatial and temporal dynamics of effective daylight in natural scenes. Journal of Vision 2022;22(14):3984.

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      © ARVO (1962-2015); The Authors (2016-present)

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In vision science, it is presumed that daylight priors affect color, shape, and light perception. Earth-Sun geometry, weather, climate, and optical effects such as Rayleigh scattering cause daylighting variations in time, direction, and space, which are well described by hemispherical models such as the CIE daylight(ing) model. These models however exclude influences such as vignetting in and (inter)reflections from the environment. These can cause the effective daylight spectral power distribution (SPD) to vary from one time and position to another. Here we aimed to quantify such effective temporal and spatial variations of intensity, direction, color and diffuseness in daylit natural scenes via cubic spectral irradiance metering. We measured the diffuse (light density) and directed (light vector) light-field components in a sunlit rural scene over a day with 5-minute intervals in experiment one, and in the shade and in the light for 24 sunlit rural and urban scenes across multiple days in experiment two. In the first (temporal) experiment, we found that the chromaticities of light densities were rather stable, but the light vectors varied from warm during dawn and dusk to cool around noon. The light vectors' directions varied systematically during daytime and were close to the sun path, while those for twilight were pointing upwards. The second (spatial) experiment revealed that the chromaticities and intensities of the light vectors in the shade and light showed larger differences than the light densities. The diffuseness in the shade was 1.1 to four times larger and the colour temperature thousands of Kelvins higher than in the light. This study demonstrates how differential contributions of the effective diffuse and directed day-light-field components can be captured and how these may vary in many ways. Vision research into color, shape, and light perception in natural scenes need to take such variations into account.


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