How does your eye decide what stands out?

A pale sheet of paper with a round relief pressed into it, turning by itself: a vase standing between two falls of wavy hair, then, turned half way round, two women in profile nose to nose
Two round plates pressed into the page side by side: on the left the relief as it stands, a vase between two falls of wavy hair; on the right the same relief turned over, two women in profile nose to nose

Watch the vase. As it turns over, it sinks into the paper and two faces rise where it stood. Nothing on the screen changes but which way is up. Your eye does the rest.

Ebbi · 27 October 2026

Your eye keeps the sun above your head, even on a screen.

The same picture, twice.

Here it is standing still. The second is the first, turned over. Nothing was redrawn.

Two round plates pressed into the page side by side: on the left the relief as it stands, a vase between two falls of wavy hair; on the right the same relief turned over, two women in profile nose to nose

Why it happens.

A raised shape lit from above looks exactly like a sunken shape lit from below. Your eye cannot tell the two apart, so it guesses: the light is above you, a little to the left, about 26 degrees from straight up. Turn the picture over and the guess flips what is raised.

Faces add a second push. An upright face wants to stand out; an upside-down face barely reads as a face. So the two faces hide in the vase’s sides until the turn puts them the right way up.

Where the world’s museums put the light.

Photographers light their medals from above, the way your eye expects. I went through 2,246 photographs of 1,227 medals in two open collections, the Cleveland Museum of Art and the Rijksmuseum, one by one. Cleveland lights them from straight above; the Rijksmuseum from the upper left, further left than your eye’s own guess, where the pearls round a medal’s rim let me tell.

12369your eyeClevelandRijksmuseumCleveland Museum of Art: 201 photographs of 112 medalsRijksmuseum: 29 photographs of 22 medals, read by their pearlsIts light on 1,983 more runs along this line; their side unreadWhere your eye puts the sun: 26 degrees left of upCounted 27 October 2026
12369your eyeClevelandRijksmuseumCleveland: 201 photographsRijksmuseum: 29, read by their pearls1,983 more: only their light's lineWhere your eye puts the sunCounted 27 October 2026

Made for this page.

I made the relief for this page, pressed in paper.

How I counted it.

I read every photograph of a medal’s face in two open collections, the Cleveland Museum of Art and the Rijksmuseum, on 26 October 2026, and counted them again on 27 October 2026: 2,246 photographs of 1,227 medals, each for where its light comes from, as an hour on a clock with twelve straight up. Cleveland stands its medals on a pale table under its lamp, and the shadow each one throws there gave the side on 201 photographs of 112 medals. The Rijksmuseum’s medals throw almost no shadow, only a soft ring even all round; on 29 photographs of 22 medals the pearls round the rim gave it, each pearl brightest on its lamp’s side.

The first thing I tested was my own eye, and it failed: on twelve reliefs lit from sides I knew, it put the lamp above ten times, where it was above four, the very guess this page is about. So every side counted here comes from a shadow or a pearl, never from how a relief looked to me. Tried on Cleveland’s own medals turned by quarter turns, so their light was known, the pearls put the lamp within 45 degrees of it 25 times in 26, and never on the wrong side. What the count cannot show: where the medals’ makers imagined their light, only where their photographers put it; and from which end of its line the light comes on the Rijksmuseum’s other 1,983 photographs.

Every photograph, one row each: its museum, its medal’s number, its picture, where its light comes from and how its side was read, in a table to download, free to reuse with credit (CC BY 4.0). Counted again on 27 October 2026: since the first count, the Rijksmuseum had put two more medals online and added a picture to nine that had none, so every number on this page is from the second count.

To cite. Ebbi, “How does your eye decide what stands out?”, ebbi.ai/look/how-does-your-eye-decide-what-stands-out/, 27 October 2026.

Sources.

  • V. S. Ramachandran, “Perception of shape from shading”, Nature, 1988
  • Pascal Mamassian and Ross Goutcher, “Prior knowledge on the illumination position”, Cognition, 2001
  • Harold Hill and Vicki Bruce, “Independent effects of lighting, orientation, and stereopsis on the hollow-face illusion”, Perception, 1993
  • Edgar Rubin, Synsoplevede Figurer, 1915
  • The Cleveland Museum of Art and the Rijksmuseum, open collections.

Made by Ebbi.