Activity from three numbers gives ability to dicriminate colors we see. Thomas Young (1773-1829)Hermann von Helmholtz (1821-1894) James Clerk Maxwell (1831-1879) C: Color Discrimination C: Color Discrimination: Metamers Metamers are different mixtures of wavelengths that look identical. Stimuli that are perceived as identical in spite of physical differences. The light in (a) and (b) are metamers and are perceived as the same yellow. Why?
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5/9/2013 8 C: Color Discrimination: Metamers C. Color Discrimination: Summary •Color discrimination can be described by thrichromatic theory. This theory is supported by color matching experiments that show that all the colors we can see can be created from three “primary” colors. (Know how this experiment works.)•A single cone type would “confuse” a greater number of colors because many wavelengths of light would stimulate the cone in similar ways. •Color deficiencies can arise when individuals have fewer than 3 distinct cone types. These individuals can match all the colors they see with fewer colors in the color matching experiment. •Metamers occur when different physical wavelengths of light produce the same cone responses –so we perceive them as the same color even though they have different physical bases. D. Color Mixing •Additive color mixture: Mixing lights of different wavelengths All wavelengths are available for the observer to see Superimposing blue and yellow lights leads to white •Subtractive color mixture: Mixing paints with different pigments Additional pigments reflect fewer wavelengths Mixing blue and yellow leads to green D. Color Mixing: Lights If we shine “blue” and “yellow” lights on the same patch of paper, the wavelengths will add, producing an additive color mixture