throughmirrorA different way of seeing
Chevreul Staircase — Uniform gray steps appear shaded along their borders.
Look closely. Let the image settle.
Light & contrast / 1839

Chevreul Staircase

Uniform gray steps appear shaded along their borders.

TRY THIS

Look at the middle of each band and then its boundaries. Each separate band is filled with a constant gray.

FOLLOW THE SOURCES

History, evidence & image credit

THE IMAGE IN THIS ARCHIVE

Mabit1

Original file & attribution · CC BY-SA 4.0

Original image downloaded from Wikimedia Commons; the downloaded file is unchanged. Gallery previews may be resized or converted to WebP; animated previews show the first frame.

Download image

Frequently asked questions

What is Chevreul Staircase?

Uniform gray steps appear shaded along their borders.

What should I look for in Chevreul Staircase?

Look at the middle of each band and then its boundaries. Each separate band is filled with a constant gray.

What explains Chevreul Staircase?

A band can seem darker at one side and lighter at the other because of its neighbors. Research shows that the full surrounding context matters; a simple account based only on local edges is incomplete.

Another way to see it

Explore this category
Checkerboard and cylinder casting a shadow, with squares A and B labeled.

Checker shadow

Edward H. Adelson

Two squares. One shade of gray. A shadow changes everything.

Black square grid separated by intersecting white corridors.

Hermann grid

Ludimar Hermann

Ghostly gray spots appear where you are not looking.

White disks at gray grid intersections over black squares.

Scintillating grid

James R. Bergen; later Bernd & Elke Lingelbach, Michael Schrauf & E. R. Wist

Black dots flicker across a grid of white dots.

Chevreul Staircase — Uniform gray steps appear shaded along their borders.

Chevreul Staircase