Meaning of Color Constancy
Color constancy is a part of the visual perception system that allows people to perceive color in a variety of conditions and to see some consistency in color.
An apple that is red in the bright morning sunlight will also appear red under candlelight and in the late afternoon, when the wavelengths of available light are actually very different. Similarly, if the apple is partially in the sun and partially in the shade, an observer will read the entire apple as red.
This allows someone to recognize the apple even though conditions have changed, and the eyes perceive the color as relatively constant.
This system is part of a larger system of subjective constancy. The brain uses subjective constancy to help people perceive objects in changing situations. This ensures that they can recognize those objects, which helps to understand the world and can also be important for security.
For example, the ability to recognize a specific shape might help someone avoid danger, and the ability to compensate for distance when viewing a scene might also be important. Subjective constancy also allows people to identify and link thematic elements, as seen when people recognize a work of art because it depicts a familiar scene.
Color constancy uses input from various cone cells on the retina. The cones are sensitized to different wavelengths of light, and the brain processes their collective data to determine what colors someone is looking at.
Colors can be influenced by available wavelengths of light and by surrounding colors, so a color can look very different depending on what is placed next to it.
This aspect of the human color perception system was discovered in the 1970s. It was actually a photographer who identified the phenomenon of color constancy, perhaps because photography often requires heightened awareness of color and available light. .
Since then, color constancy has been studied extensively to learn more about how people see color and how color perception can be distorted.
Many examples used to demonstrate color constancy and tricks that can be played with color use a grid known as Mondrian.
The grid consists of a series of squares, with the experimenter manipulating the available light levels to see how people perceive the colors of the squares. An orange square, for example, can appear red at a different wavelength, and squares of the same color can appear different, depending on the colors that surround them.