A Mach band is an optical illusion, named after Ernst Mach. It is the region encircling a bright light which in visual perception appears lighter or darker than its surroundings, in a zone where the luminance increases or decreases rapidly. An optical illusion is a type of illusion characterized by visually perceived images that are deceptive or misleading [1]. Information gathered by the eye is interpreted by the brain to give the perception that something is present when it is not. ... Ernst Mach Ernst Mach (February 18, 1838 – February 19, 1916) was an Austrian-Czech physicist and philosopher and is the namesake for the Mach number and the optical illusion known as Mach bands. ... The word luminance, a synonym for luminosity, means emitting or reflecting light. ...
Although the physical brightness is constant over the distance from the ambient object, the observer perceives an "undershoot" and "overshoot" in brightness at what is physically a step edge. Thus, at a certain point, the observer perceives a slight decrease in brightness compared to the true physical value. After that point the observer undergoes a slight overshoot in brightness compared to the true physical value. The total effect is one of increased, local, perceived contrast at an edge in brightness. It is caused by lateral inhibition of the receptors in the eye. An inhibitor is a type of effector that decreases or prevents a chemical reaction. ...
It is theorised that the Mach band may be responsible for moths' attraction to ambient objects. A moth is an insect closely related to the butterfly. ...
References
[[|Lotto RB, Williams SM, Purves D, ]], () ({{{Month}}} 1999). [ Mach bands as empirically derived associations]. Proceedings of the National Academy of Sciences 96 (9): 5245-50. . PMID 10220451 The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences. ...
Ernst Mach (February 18, 1838 – February 19, 1916) was an Austrian physicist and philosopher and is the namesake for the "Mach number" (aka Mach speed) and the optical illusion known as Machbands.
Mach returned to the University of Vienna as professor of inductive philosophy in 1895, but he suffered a stroke two years later and retired from active research in 1901, when he was appointed to the Austrian parliament.
Mach's paper on this subject was published in 1877 and correctly describes the sound effects observed during the supersonic motion of a projectile.
Mach number Ratio of the speed of a body or fluid to the local speed of sound.
Mach, one of the leaders of modern positivism, did his major work in the philosophy of science.
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