[jawns]

You need to make a distinction between color of the shoe (under normal lighting conditions) and pixel values of the shoe in the photograph.

The shoe is pink under normal lighting conditions, but the pixel values are green-gray in the photograph, where the lighting has been manipulated.

So, if you were to use a color-dropper tool on the photograph, you would get green-gray values for those pixels.

But some people are able to do color-correction in their minds and determine that the underlying color of the shoe (under normal lighting conditions) is pink. Indeed, the automatic color correction that occurs as they visually process the image is so strong that they find it hard to recognize that the actual pixel values are green-gray.

Yet when the color of the socks is changed to white, but nothing else about the photograph is altered, the visual cue that prompts them to do color-correction in their minds disappears, and they perceive the shoe color in the photograph to be green-gray, just as others do.

[notfed]

I'm still not convinced. They said the answer is pink. But...it wasn't pink, even to their own admission. A pink shoe, when placed under pure-green lighting is no longer pink: at this point we're out of illusion territory and into lighting trick / semantics territory.

If they'd have said the answer is green-gray, then fine, this would be an illusion for those people who incorrectly thought the shoes are pink, but their answer is still wrong.

[krsrhe]

The picture is gray, but the actual shoes are pink, but bathed in green light. Some people sometimes can mentally remove the green lighting.

[dsr_]

To do this properly, then, they should use video instead of stills.

Have a nice white background. White socks, pink shoes. Slowly move a green spotlight across the scene.

[drdec]

This is what I don't understand. I thought the socks were green, not white in green light, and still thought the shoes were pink.