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Equal central disks surrounded by circular outlines of different diameters.
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Size & geometry / 1865

Delboeuf rings

A surrounding ring changes the apparent size of a disk.

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Compare the inner disks. A close outer ring and a distant outer ring can make equal centers appear unequal.

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History, evidence & image credit

THE IMAGE IN THIS ARCHIVE

Washiucho

Original file & attribution · Public domain

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Frequently asked questions

What is Delboeuf rings?

A surrounding ring changes the apparent size of a disk.

What should I look for in Delboeuf rings?

Compare the inner disks. A close outer ring and a distant outer ring can make equal centers appear unequal.

What explains Delboeuf rings?

A nearby boundary can pull perceived size toward the surrounding shape, while a more distant boundary can create contrast. The direction and strength of the effect vary with the spacing of the rings.

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Equal central disks surrounded by circular outlines of different diameters.

Delboeuf rings