"This image is an illustration of the opponent process theory of vision. The image depicts the Canadian flag. Where the familiar Canadian flag is a red maple leaf on a white background bordered by two white columns this image is different. It shows a green maple leaf on a black background bordered by green columns. If a person stares at the green and black flag and then diverts their eyes to a blank surface such as a wall an ""after image"" of the Canadian flag will appear to hover there, only it will appear in red and white! Exactly the opposite colors the person was just staring at."
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