Aerial Perspective - Optics

Optics

The major component affecting the appearance of objects during daylight is scattering of light, called skylight, into the line of sight of the viewer. Scattering occurs from molecules of the air and also from larger particles in the atmosphere such as water vapor and smoke (see haze). Scattering adds the sky light as a veiling luminance onto the light from the object, reducing its contrast with the background sky light. Skylight usually contains more short wavelength light than other wavelengths (this is why the sky usually appears blue), which is why distant objects appear bluish (see Rayleigh scattering for detailed explanation). A minor component is scattering of light out of the line of sight of the viewer. Under daylight, this either augments the contrast loss (e.g., for white objects) or opposes it (for dark objects). At night there is effectively no skylight (unless the moon is very bright), so scattering out of the line of sight becomes the major component affecting the appearance of self-luminous objects. Such objects have their contrasts reduced with the dark background, and their colours are shifted towards red.