Mixing in the EyeOptical Mixture

The Impressionists rarely mixed green on the palette. They placed small dots of yellow and blue side by side on the canvas and let the viewer’s eye produce the green. The dots had to be small. That is the whole point. The effect depends on scale.

How it works

At close range, you see two distinct colors. At a distance — or when the elements are fine enough — the colors cancel each other and a third color emerges, the mixture, present nowhere on the surface. This is optical mixture: colors combining not on the palette, not in the imagination, but in the eye.

Make the stripes coarse and you see two colors plainly. Make them fine enough and the two fuse into a single intermediate color.

The same trick, industrialized

Every full-color print you have ever held works this way. The pages of a magazine are not painted; they are sprayed with microscopic dots of cyan, magenta, yellow, and black ink. Your eye does the mixing. A halftone newspaper photograph conjures a continuous grey from nothing but binary black dots on white paper.

What painters discovered, the printing press industrialized. And the screen in your hand does it too. RGB sub-pixels too small to resolve mix in the eye to produce every color the display can show.

The variables are the size of the elements and the viewing distance. Increase either and distinct colors merge; decrease either and the mixture separates back into its parts. Mosaics, tapestries, knit patterns, pixel art, dithering algorithms — the same principle is at work in all of them.