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Contrast Enhancement at Borders

  • By: Stephen L. Macknik & Susana Martinez-Conde
  • In: Encyclopedia of Perception
  • Edited by: E. Bruce Goldstein
  • Subject:Sensation & Perception

Nineteenth-century visual scientists such as Michel-Eugène Chevreul, Ernst Mach, Hermann von Helmholtz, Ewald Hering, and Johannes Peter Müller discovered that simultaneously presented stimuli could affect each other's perceived contrast. For example, notice how each of the solid stripes in Figure 1 appears lighter on the left than on the right, even though each stripe has the same physical intensity across its width. This illusion is called “Mach bands,” and it illustrates how the contrast of a stimulus is enhanced at its borders. This entry describes spatial and temporal contrast enhancement at borders.

Spatial Contrast Enhancement at Borders

Visual spatial contrast is the perceived difference in brightness or color between two or more locations in the visual scene. Perceived contrast is determined by the physical difference in intensity ...

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