Optical illusion: Seeing color in a black-and-white image

Stare into the black circle in this video to get a lesson in chromatic adaptation from scientist Andrew Steele.

This is definitely my favourite optical illusion-it's mind-bendingly effective but infuriatingly ephemeral, vanishing as soon as you try to look straight at it-and a fantastic illustration of how our eyes and brain together conspire so that what we see and reality aren't as synonymous as we like to think.

(Nag on the Lake)

screengrab via Andrew Steele/YouTube