Irradiation illusion

The irradiation (Latin, radiation ') is an optical illusion that causes bright objects larger and dark objects appear on a dark background on a light background smaller than they actually are.

The name of this deception of vision comes from Hermann von Helmholtz, who attributed the phenomenon to the scattering of light in the eye, causing a bright area of the visual field can irritate a larger area on the retina than an otherwise identical, but darker area.

Basics

The Irradiationswirkung evident each distance of the perceived object and the apparent magnification is all the more striking, the brighter it appears in the visual field; However, it takes above a corresponding approximately to the daylight illumination density is not more clearly. According to Helmholtz ' statements 1867 range as an explanation towards the circles of diffusion through the dioptric apparatus of the eye, which still occur even with perfect accommodation as a result of spherical and chromatic aberration of the eye. Joseph A. F. Plateau had adopted a propagation of the light impression on the retina of our eye for irradiation in 1839 and attributed them as a visual illusion of receptive processing of the retinal image. The phenomenon itself, however, was known as hallucination earlier; it mentions Galileo Galilei in 1632 in his Dialogue on the Two Chief World Systems.

Examples

It is observed that irradiation particularly striking in the dark night to the light of the crescent moon shape, which seems to belong to a disk of larger radius than the rest of the moon; Therefore, the tips of a thin crescent occasionally appear as if they would reach over half - an aspect which is called luna cornuta, croissant -shaped moon, or an effect of irradiation, leading to a misinterpretation of the geometry of the day - night boundary ( terminator) can cause the moon.

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