Mach bands are an optical illusion where a band of gradients will appear in places to be lighter or darker than they actually are. Mach bands, as well as numerous other visual and perceptual illusions, provide a valuable way to investigate how the eye and brain process visual information. Equally, they are used by artists for visual effect, entertaining and satisfying the endless fascination human beings have with novelty and creativity.
Mach bands were discovered by the Austrian physicist Ernst Mach. Mach is known for his work in optics, mechanics, and wave dynamics, as well as notable advances in the field of supersonic travel (the Mach number is also named for him). Mach discovered the physiological phenomenon of Mach bands during the 1860s.
When looking at Mach bands, one sees a central band of a light to dark gradient surrounded on one side by the lightest color and on the opposite side by the darkest color. When looking at this gradient, one sees a band along both the light edge that appears to be lighter than the solid field surrounding it, and a band along the dark edge that appears darker than its surroundings. In reality, there is no color darker or lighter than the surrounding fields.
The explanation of Mach bands is often based on the concept of lateral inhibition. Lateral inhibition is a process by which the collection of light by retinal cells in the eye is affected by the light collection of neighboring cells. In nature, this helps boost the perception of object edges, making it easier to see the edge of an object that might otherwise not be noticed.
An alternative explanation of Mach bands has to do with the way the eye and brain perceive highlights and lowlights, creating harmonics in the visual waveforms that merge in certain areas and create the illusion of darker or lighter sections.
Mach bands, as well as numerous other visual and perceptual illusions, help scientists study the way the eye and brain process visual information.
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