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Notice the grid of black, white and two shades of blue. Would you believe that all the blue is precisely the same shade of blue, instead of there being some light blue bars and some dark blue bars? There are endless variations of this color contrast illusion, which is sometimes called the Munker-White Illusion and sometimes the Bezold Effect. When the shades involved are black, white and grey the same illusion is called White's Illusion. If you are skeptical about there being only one shade of blue, click
A good interactive version of this illusion can also be found here, on a site which collects many very nice illusions. And more colorful examples are found here. If you can't wait for next week's illusion, click here. |
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The classic example of the Bezold Illusion or Bezold Effect is shown above; the bricks are essentially identical in both images, but where the mortar is black the bricks appear to be brighter shades of red, as compared to the otherwise identical image where the mortar is white.
How about ending with a variant? You should see 3 different shades of blue; of course, there is only one. Also notice on the central blue vertical bar the “ghost images” of the horizontal black bars.
Prof. Michael Bach has an animated, interactive version of this so-called Munker Illusion, here.