Like apparent motion, color vision is also subject to unusual effects. When day gives way to night, twilight brings what the poet T.S. Eliot called the violet hour. A light levels fall, the rods become progressively less responsive. Rods are most sensitive to the shorter wavelengths of blue and green, and they impart a strange vividness to the gardens blue flowers.
However, look at a white shirt during the reddish light of sunset, and youll still see it in its true colorwhite, not red. Our eyes are constantly comparing an object against its surroundings. They therefore observe the effect of a shift in the color of illuminating on both, and adjust accordingly.
The eyes can distinguish several million graduations of light and shade of color. Each waking second they flash tens of millions of pieces of information to the brain, which weaves them incessantly into a picture of the world around us.
Yet all this is done at the back of each eye by a fabric of sensors, called the retina, about as wide and as thick as a postage stamp. As the Renaissance inventor and artist Leonardo da Vinci wrote in wonder, Who would believe that so small a space could contain the images of all the universe?
1.Visual illusions often take place when the image of reality is ___.
A.matched to six to seven million structures called cones.
B.confused in the bodys sensors of both rods and cones.
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