Benham's Disk - Spinning Disk Colors

Did you know that black and white flashes can be seen as color?

Gustav Fechner and Hermann von Helmholtz were the first to notice that colors can be seen while spinning a disk which is painted black and white. The effect is not well understood and is known under various titles including "subjective colors," "Fechner-Benham colors," "Prevost-Fechner-Benham colors," "polyphan colors," and "pattern-induced flicker colors" (PIFCs).

The effect didn't become famous until a toy manufacturer happened to notice colors being produced by a special pattern that was drawn in black and white on a spinning toy top. Mr. Charles E. Benham, an English toy-maker noticed these colors on the spinning tops in 1894. He called his top an "Artificial Spectrum Top," but it naturally became known as "Benham's Top" and was sold by Messrs. Newton and Co. Toy spinning tops with Benham's disks are still available in the some toy stores.

Trying This At Home

If you want to make your own Benham's top and can't find a toy top to paint, you can easily create your own top at home with some materials you are likely to have handy.

What you need:

Paper

Piece of Cardboard

Toothpick

Glue

Black Marker

Scissors

Glue the piece of paper to the cardboard. Poke the toothpick straight into the center of the paper/cardboard and glue it in place, half above and half below.

Let it dry.

Draw a circle about 6" in diameter on the paper/cardboard and cut it out.

With the marker, draw a pattern on the paper like the one you see here. Or use the pattern like this Benham's Disk.

Try spinning the "top" in a brightly lit room or outside in the sunlight. Watch the disk as it slows down to see the different colors.

Why It Works

After more than 100 years, we are not sure what causes this effect. There are different theories.

One theory says that, the different cone cells react to the colors at different rates and stay active for different amounts of time. When the top is spun, the white activates all three types of cones, then the black deactivates them. This causes an imbalance and confuses our brain, causing us to see colors which are not there.

Another theory is that the black and white on the top stimulate different parts of the retina. As our response alternates between black and white, it may do something to our nervous system which generates color.

For more information you might look for the following book at your local library: Seeing the Light, by David Falk, Dieter Brill, and David Stork (Harper & Row, 1986)

Different people see different patterns of color and we are not sure why that happens, either.