Optical Illusions

You can't depend on your eyes when your imagination is out of focus.

- Mark Twain

Our brain tries to make sense of the information detected by our eyes. When the optic nerve sends the brain a message, it uses its memory bank to help interpret the message. The brain compares information in its memory bank to previous experiences. It also uses clues such as colours, shadows, shapes, and perspective. Sometimes the brain is tricked by a confusing message, or by "puzzle pictures". These are called optical illusions.

Both of the above images are based on the same optical illusion.  Can you see what it is?

The Dutch artist M.C. Escher mixed realistic detail with strange perspectives that also provide optical illusion's.  Below is an image that Escher created in 1961.

Waterfall - 1961

Movies are a series of still pictures that we see one after the other. Movies move at a rate of 24 pictures per second, and provide the illusion of movement.