Checkerboard Illusion Makes You See Two Different Colors
August 18, 2011
If there's one thing you think you know, it's color. No matter what happens, red is still red, blue is still blue, and pink is still a strange color for a dude to wear. And you'd be right...except sometimes not.
Go ahead, watch that video. Go on, we'll wait. Okay, we'll wait a little longer until you go check your eyes. No, it's not CGI. It's an optical illusion that shows how your brain differentiates different shades of color.
It works using the following techniques. First, there's “local contrast.” Basically, if a lighter color is surrounded by darker colors, your eye is naturally going to perceive it as lighter, and vice versa. So, the check you see as “dark” is surrounded by lighter colors, while the check you see as “light” is surrounded by darker colors.
Next there are the edges. The shadow has a soft edge that gradually fades to a much darker color, but the checks have sharp lines that are easy for your eye to see. Your eye tends to ignore light levels when figuring out color because it doesn't want to get misled by shadows. The sharp edges of the checks also announce to your mind that there is a sharp color change, right at that junction, so your mind sees what it expects to see.
It's incredibly freaky, but utterly awesome at the same time.