Wednesday, August 8, 2012

Mach band effect



You've heard of the CSI effect. It tends cause problems in getting folks back to reality. Part of the problem is that folks believe what they see, both on TV and in front of them as they sit in the jury box. But is seeing really believing?

What we're seeing here is the Mach band effect - where apparent brightness is not uniform (transitions seem brighter on the bright side and darker on the dark side). This effect was first described by Ernst Mach, the famous supersonic physicist that gave us the Mach numbering system (M=V/a). The undershoots and overshoots (red line) illustrate the effect.

Remember that this is a perceived effect. The change in luminance is a hard step. The change in brightness has the under/over shoots - giving the appearance of a gradient. Remember, brightness and luminance aren't the same thing.

Want to see more? Click here to head over to Duke University and see for yourself.

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