Amazing optical illusions

An optical illusion.This site contains over 60 amazing optical illusions. Here is an example.

What to do:
    You will, in all likelihood, perceive the left picture as a 3-dimensional scene, where a greenish cylinder stands on a checkered plane; light comes from top left. Two patches will be indicated (left picture), and you are asked to compare their relative brightness. I think we can all agree that the top one is darker.

    A second later, a yellow mask will appear (right picture). Now you can compare the two patches without the 3-dimensional context. Now the brightness will be identical. The luminance is identical at all times, but the brightness (=apparent luminance) differs, depending on context.
    When interpreted as a 3-dimensional scene, our visual system immediately estimates a lighting vector and uses this to judge the property of the material.

Check out the other optical illusions which appear to animate from the following link.

Link & Image: Optical Illusions
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