Optical Illusions: Distortions - continued

EluZions.com Illusions Distortion : Wall

Hering's Optical Illusion

The slanted lines cause the illusion; because if you removed them you could easily see that the two horizontal lines are parallel. The arrowheads are distorting our perception. Imagine them extended, as if to form the edges of a box or room. Then the outward slanting ones would be the `far corner'. Because we take distance into account when judging size, when two objects project the same image size on the retinas of our eyes, we interpret the object that seems farther away as larger.

Zöllner

F. Zöllner, an astronomer, discovered an illusion on a cloth pattern. Zöllner's illusion shows that parallel lines intersected by a pattern of short diagonal lines appear to diverge. As with many distortion illusions, this one is most easily explained if we assume that the brain is attempting to interpret this image as if it were part of a three-dimensional scene. The short horizontal and vertical lines make the oblique lines appear to be part of some vertical and horizontal planes respectively, receding into the distance, shrinking with the perspective effect.

Poggendorf

In 1860, J. C. Poggendorf, the editor of a journal of physics and chemistry, received a monograph from Zöllner describing his illusion. Poggendorff noticed and described another effect of the apparent misalignment of the diagonal lines in Zöllner's figure. Thus the Poggendorff illusion was discovered. The single line if continued joins with the lower of the pair, not the top.

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