Black and white are pretty straightforward until you see the colors on a Benham Disk. Then, it could be any color–green, yellow, blue, red or even violet.
See what I mean in the video below:
This disk has confounded people for over one hundred years. It’s a black and white disk of paper. How are we seeing different colors when it spins?
Back in 1894, Mr. C.E. Benham sold his disk as a children’s toy top. Half the disk was painted black and the other half was white and drawn with a dozen 45-degree concentric arcs. The arcs were divided evenly into quadrants–three arcs in each quadrant.
When the top was spun, different colors appeared in the circles. Strangely, the colors couldn’t be photographed, but the colors did change depending on speed and direction.
The disk’s design was purposeful, yet no one could figure out how the colors appeared. In 1894, the mystery amazed children and adults. Even in our high tech age, watching colors appear on a black and white top is still mesmerizing.
Benham was selling a magic toy, but there it’s a scientific principle at work. Before Benham figured out he could make a lot of bucks with the disk, the appearing colors were discovered by Gustav Fechner and Hermann von Helmholtz. The colors have been known by several names, such as “subjective colors,” “Fechner-Benham colors,” “polyphan colors,” and “pattern-induced flicker colors” (PIFCs).
It happens because the eye tricks the brain. Our retinas contain cones and rods; cones help us see colors and in bright light, while rods help us see in monochrome and in low light. There are three different types of cones–one perceives red, one perceives blue and the third helps us see green–and they all work at different speeds and lengths of time.
Even now we don’t entirely know how the Benham disk works, but the theory is that it stimulates the different cones and rods in patterns. If you look at one spot on the disk as it spins, you will see flashes of white, then black, because of the activation of the cones and rods. Because the cones function at varying speeds, the flashes start to appear as colors.
It’s easy to make your own disk at home. Or use an online version to see how the rotation will create the illusion of colors. No matter what, though, when it stops, it’s really only black and white.
Which shows what we visually perceive is not always so straightforward…not so black and white.