Surface Illumination
The spectrum of surface illumination depends upon solar elevation due to atmospheric effects, with the blue spectral component from atmospheric scatter dominating during twilight before and after sunrise and sunset, respectively, and red dominating during sunrise and sunset. These effects are apparent in natural light photography where the principal source of illumination is sunlight as mediated by the atmosphere.
According to Craig Bohren, "preferential absorption of sunlight by ozone over long horizon paths gives the zenith sky its blueness when the sun is near the horizon".
See diffuse sky radiation for more details.
Read more about this topic: Sunshiny
Famous quotes containing the words surface and/or illumination:
“White Pond and Walden are great crystals on the surface of the earth, Lakes of Light.... They are too pure to have a market value; they contain no muck. How much more beautiful than our lives, how much more transparent than our characters are they! We never learned meanness of them.”
—Henry David Thoreau (1817–1862)
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—John Adams (1735–1826)