Optical Illusion

I was reading Bad Astronomy a few minutes ago, and Phil Plait had a post there that tangentially touched on optical illusions. It reminded me of an optical illusion that I created a couple of weeks ago when I was learning how to program scenes in POV-Ray. Here it is. You can see that this picture has a lot of color in it. From about a foot away, stare at the center of the image for a few seconds. Do you see it turn into shades of gray?


I don't know what the name of this type of illusion is. If anyone knows, I'd appreciate it if they left a comment.

Update: Thanks to Barun Vurdlak for featuring this image as the illusion of the day at Mighty Optical Illusions blog. Apparently this illusion is related to the Hybrid Images illusion and the Color Adapting illusion.