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FunctionUsed by Land for his experiments with color vision (Retinex theory).
Mach bands are an optical effect (often called illusion) named after Ernst Mach. Mach used a wheel with black and white sectors that, when spun, generated a linear gradient in gray tones, linking a uniformly lighter region (near the center of the disk) to a uniformly darker region (near the periphery). Mach bands are most often referred to horizontal or vertical bands that appear lighter or darker than justified by the underlying light. The effect is one of increased, local, perceived brightness on either side of a luminance gradient. Here, owing to the different sizes of the colored squares, the spinning disks generate various linear gradients of gray and yellow.
ProvenanceThis object belonged to Edwin H. Land and came from the Rowland Institute, Harvard University. Gift of the Edwin H. Land Family.
Related WorksR. Beau Lotto, S. Mark Williams and Dale Purves, "An Empirical Basis for Mach Bands," Proceedings of the National Academy of Sciences of the United States of America 96 (1999), 5239-5244.