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A series of gray regions or gradients with apparent bright and dark bands at their transitions.
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Light & contrast / 1865

Mach bands

Brightness bands appear where the shade changes.

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Look near the transitions between neighboring gray regions. The apparent light and dark rims exaggerate the actual brightness profile.

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History, evidence & image credit

THE IMAGE IN THIS ARCHIVE

DancingPhilosopher

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Frequently asked questions

What is Mach bands?

Brightness bands appear where the shade changes.

What should I look for in Mach bands?

Look near the transitions between neighboring gray regions. The apparent light and dark rims exaggerate the actual brightness profile.

What explains Mach bands?

Vision emphasizes changes in luminance near transitions. The resulting perceived bands can be stronger than the underlying gradient. Retinal and broader spatial-processing accounts explain aspects of this edge enhancement.

Another way to see it

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A series of gray regions or gradients with apparent bright and dark bands at their transitions.

Mach bands