Hering Illusion

From Michael’s “Optical Illusions & Visual Phenomena”

 
←The standard Hering illusion (1861).

Placing the mouse over the image causes the oblique lines to disappear, revealing the fact that the red bars were completely straight all the time.

 
The picture on the right is a mess to look at. But if you place the mouse over it, you can see how beautifully it changes the apparent orientation of the red squares.

This is a dynamic variation of “Three in One” by Hans Kuiper which, in turn, is based on “Square of Three” by Reginald H. Neal (colour lithograph, 1964).

 
←And another variant, a combination of Hering’s and Zöllner’s illusion. Again, judge the straightness of the lines, then place the mouse over the image.