Ehrenstein illusion

In the discovery of the optical illusion, Ehrenstein found that grating patterns of straight lines that stop at a certain point appear to have a brighter centre, compared to the background. Ehrenstein published his book Modifications of the Brightness Phenomenon of L. Hermann to disprove Hermann's theory. He argued that these illusions were not caused by a contrast effect, but rather a brightness effect that needed to be further explored. The Ehrenstein illusion can be classified as a brightness illusion. The borders of a shape affects the observed brightness of an image surface. These effects vary from person to person and can be further enhanced by changing the background of the configuration, or the surroundings of the image surface. The observer perceives the luminance of a surface to be brighter, despite it being identical to the background. Sometimes the "Ehrenstein" is associated with an illusory contour figure where the ends of the dark segments produce the illusion of circles or squares.