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But why does this happen? And above all, now that we know that A and B are identical, why do we continue to perceive them as different colors when we look at the chessboard? The reason lies in the nature of color for our visual system, which in this operation tries to determine the degree of gray of the squares on the chessboard. A white surface in the shade, in fact, reflects less light than a black surface in bright light . Therefore, to decide where the shadows are and how to compensate for their presence to determine the shade of gray of the surface, our visual system must resort to some tricks. The first is based on local contrast.

In both light and shade conditions, a square that is brighter than its neighbors is probably perceived as brighter than average and vice versa. In our illusion the light square in the shade B is in fact surrounded by black squares. This means that, although the square is seo expater bangladesh ltd physically dark, it appears brighter when compared to its neighbors. On the contrary, the black squares, outside the shadow cast by the green cylinder like square A , are surrounded by brighter squares, which appear darker in comparison.



Furthermore, our visual system tends to ignore gradual changes in light intensity in order to determine the color of a surface without being misled by shadows. In the specific example, the shadow drawn on the chessboard is calibrated so as to darken the light squares, making them equal to the dark ones. The brain interprets the context of the image and becomes convinced that it is a shadow, as the object casting the shadow is visible. Furthermore, we know how a chessboard is made: there are white squares and black squares, one next to the other at regular intervals.