AHCA1233 Colour Study L2 7 MAY 2012 - Color Physics and...

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Unformatted text preview: Color Physics and Perception Chapter 2 09/07/16 1 The sensations of color do not exist without light. Light is composed of quanta, which called has photons, meaning “light”. Photons behave as waves travelling with different frequencies or wavelengths. 09/07/16 2 Different wavelengths of light, differently, color are composed of photons of energies. Shot wave region of the spectrum have the most energy. Long wave photons have least energy. 09/07/16 3 The Human Eye 09/07/16 4 The eye is a very complex receptor that sends its information as electrical impulses to the brain, which in turn makes sense of these various stimuli. 09/07/16 5 The eye is and organ that is adapted detect light. Light enters the eye through the pupil and falls on the retina, the inside back of the eye. The retina is made up of two kinds of light sensitive receptor cell, rod and cones. 09/07/16 6 Both rods and cones connect to the optic nerve, which transmits the sensory message from the eye to the brain. Cones dominate vision when a great deal of light is present. And rods dominate vision in low light. 09/07/16 7 Cones are responsible for color vision and for the ability to see detail. Rods are responsible for peripheral (surrounding, less focused) vision. The fovea is a tiny area at the back of the eye that contains only cones. It is the center on the visual field. 09/07/16 8 The fovea is the most sensitive area of the retina. It detects patterns of light , dark and color with the greatest clarity. The sensation of light is received in two areas of the brain: the cerebral cortex and the hypothalamus, or midbrain. 09/07/16 9 The cerebral cortex is the center of cognitive activity. It receives information and processes it: recognizing, identifying and structuring a response to each stimulus. The midbrain controls the internal environment of the human body. 09/07/16 10 Sensation of light transmitted to the center for regulation of blood pressure and body temperature. It also stimulates glands that control the production and release of hormones. When the brain is stimulated by a thought, mental image, or outside stimulus (like light), the midbrain triggers the release of hormones. 09/07/16 11 This response means that a color stimulus has an effect on the strongest human needs and emotion-stress, hunger, thirst and sex. Changing the strength of a color stimulus causes a change in the body. 09/07/16 12 Exposure to an elevated level of red wavelength stimulates hormone production and raises blood pressure and depresses hormonal secretions. Because exposure to color changes the body’s hormonal balance. It also cause changes in behavior. 09/07/16 13 Color can be chosen to stimulate, depress, or otherwise alter mood. A graphic designer may choose a high level of stimulation to draw attention. Restaurant designers use red to stimulate the appetite. 09/07/16 14 The Human Eye and Color. The colors of the rainbow Normal color vision The colors of the rainbow Tritanope (simulation) Absence of blue retinal receptors The colors of the rainbow Protanope (simulation) Absence of red retinal photoreceptors The colors of the rainbow Deuteranope (simulation) Absence of green retinal photoreceptors Trichromats Humans have three kinds of color receptor cells – or “cones” - in their eyes. Each type of cone contains a different visual pigment. These three cone types are called "red", "green" and "blue." Therefore, we are “trichromats” (tri = 3, chroma = color). (All hues can be produced by mixing red, green and blue light. This is how a color television set works; a mixture of these three wavelengths of color produces several million visible colors.) Trichromats (with a special sensitivity to ultraviolet) Some animals – for example bees – have three types of cones. Two of the cones are sensitive to "human visible" wavelengths. The third cone is sensitive to colors in the ultraviolet range of the spectrum. This cone enables them to see colors that humans can’t see. They also perceive humanvisible spectra in different hues than those that humans experience. Tetrachromats Most bird species (that have been studied) have at least four types of cones. They are "tetrachromats." Recent studies have confirmed tetrachromacy in some fish and turtles. Perhaps it is mammals, including humans, that have poor color vision! It has been suggested that some women are also tetrachromats. One study suggested that 2-3% of the world's women may have the kind of fourth cone that gives a significant increase in color differentiation. Another thing to consider: Some data suggests that the architecture of the human visual system (as well as that of many animals) is really tetrachromatic - but that this capacity is blocked. Dichromats Many animals have only two kinds of cones in their eyes. They are known as “dichromats.” It’s worth noting that the color-sensing pigment in these cones may be weak. Therefore, an animal – for example a dog - probably sees very weak colors. What is Color-Blindness? Color-blindness is the inability to distinguish the differences between certain colors. This condition results from an absence of color-sensitive pigment in the cone cells of the retina, the nerve layer at the back of the eye. Most color vision problems are inherited and are present at birth. Approximately 1 out of 12 males and 1 out of 20 women are color blind. What does a color-blind person see? A person with color-blindness has trouble seeing red, green, blue, or mixtures of these colors. The most common type is red-green colorblindness, where red and green are seen as the same color. Here are some illustrations of the most common forms of color-blindness. Tests for Color Blindness The typical test for color-blindness is based on a person's ability to see numbers inside a circle. Here is a sample of charts used to test for color-blindness. There is a number in the center of the circle. If you can see a number in three of these circles, chances are you are not color blind. Plate 1 What number do you see? Plate 2 What number do you see? Plate 3 What number do you see? Plate 4 What number do you see? Plate 1 Those with normal color vision should read the number 74. Plate 2 Those with normal color vision should read the number 6. Plate 3 Those with normal color vision should read the number 29. Those with red-green deficiencies read the number 70. Those with total color-blindness can not read any number. Plate 4 Those with normal color vision should not be able to read any number. Most of those with red-green deficiencies should read the number 5. Those with total color blindness can not read any number. Color Therapy - Color and the Brain Specific colors have different effects (list copied from Biopulse.org) Black: self-confidence, power, strength. Blue: calming, lowers blood pressure, decreases respiration. Green: soothing, relaxing mentally as well as physically, helps those suffering from depression, anxiety, nervousness. Violet: suppresses appetite, provides a peaceful environment, good for migraines. Pink: used in diet therapy as an appetite suppressant, relaxes muscles, relieves tension, soothing. Yellow: energizes, relieves depression, improves memory, stimulates appetite. Orange: energizes, stimulates appetite and digestive system. Red: stimulates brain wave activity, increases heart rate, respirations and blood pressure. Healing and Color The eye is not the only organ that responds to light. Light is also absorbed through the skin. The use of colored light to act on the body through the skin is a routine medical practice. The treatment of jaundiced infants with light is a standard( and effective) therapy, as is the treatment of psoriasis, a skin disease, by exposure to sunlight. Ancient Greeks used a purple dye extracted from shellfish as a treatment for ulcer. ...
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