Chapter 09 Perceiving Color

Name Clas Dat e: b Chapter 09: Perceiving Color Multiple Choice 1. When you go to pick strawberries, you are easily able to separate the ripe red berries from the green foliage, the white blossoms and the green, still-forming berries. This has led to the suggestion that a. we need experience with the natural world in order to experience color vision b. the genes resulting in lack of color vision should have disappeared long ago c. color vision may have evolved for the express purpose of detecting fruit d. only herbivore species should have color vision ANSWER: 2. A monkey with good color vision a. would have difficulty with figure-ground segregation b. would have a better chance of surviving than a color-blind monkey c. would have an equal chance of survival as a color-blind monkey d. would be very atypical, since most monkeys are color-blind ANSWER: 3. Adding more white to a color changes the color's a. b. hue wavelength C. brightness d saturation ANSWER: 4. The basic colors in the color circle are a. red, white, blue and green. b. black, white, and gray C. red, green, and blue d. red, green, blue, and yellow d ANSWER: 5. By changing we can create about a million (or more) discriminable colors. a. saturation only b. value only C. hue and saturation, but not value d. saturation, value, and hue d ANSWER: 6. The reflectance curve is a plot of the light reflected off a surface as a function of a. spatial frequency b. contrast wavelength d. orientation d Page 1 Name Clas Dat e: Chapter 09: Perceiving Color ANSWER: 7. The reflectance curve for a white piece of paper would reflect a. mostly short wavelengths, a moderate amount of medium wavelengths, and a little of the long wavelengths b. mostly long wavelengths, a small amount of medium wavelengths, and a little of the short wavelengths c. a little of short wavelengths, a large amount of medium wavelengths, and a little of the long wavelengths d. long, medium and short wavelengths equally ANSWER: 8. The reflectance curve for a purple piece of paper will reflect short wavelengths b. long wavelengths only c. all wavelengths equally d. long and short wavelengths d ANSWER: 9. Yellow and blue light is projected on a white screen. What color will the screen appear to be? а. white b. gray c. green d. purple d ANSWER: 10. Light that is mixed is referred to as a(n) electromagnetic color mixture b. additive color mixture c. subtractive color mixture d. transitive color mixture ANSWER: 11. Paint that is mixed is referred to as a(n) a. viscous color mixture b. additive color mixture с. subtractive color mixture d. pigmented color mixture b ANSWER: 12. Blue and yellow paints mixed together yield a. white b. gray с. green ANSWER: d. purple Page 2 Name Clas Dat e: Chapter 09: Perceiving Color experience is built from four primary chromatic colors that are arranged into two opponent pairs: yellow-blue and red-green. In addition to these chromatic colors, Hering also considered black and white to be an opponent achromatic pair. 55. Does retinal physiology support the trichromatic theory, opponent-processing theory, or both? Support your answer. ANSWER: Our experience of color is shaped by physiological mechanisms both in the receptors and in opponent neurons at the level of the retina. Trichromatic theory is supported by color matching at the level of receptors while hue cancellation, which supports opponent-process theory occurs in opponent cells. Hence, retinal physiology supports both theories. 56. Evaluate Newton's claim that the light "rays...are not colored." ANSWER: Newton's idea is that the colors we see in response to different wavelengths are not contained in the rays of light themselves, but that the rays "stir up a sensation of this or that color." Stating this idea in modern-day physiological terms, we would say that light rays are simply energy, so there is nothing intrinsically "blue" about short wavelengths or "red" about long wavelengths, and that we perceive color because of the way our nervous system responds to this energy. We can appreciate the role of the nervous system in creating color experience by considering not only what happens when vision shifts from cone to rod receptors but also the fact that people like Mr. 1., the artist who lost his ability to see color in a car accident, see no colors, even though they are receiving the same stimuli as people with normal color vision. Also, many animals perceive either no color or a greatly reduced palette of colors compared to humans, and others sense a wider range of colors than humans, depending on the nature of their visual systems. 57. Discuss the methods and results of Uchikawa et al.'s (1989) research on chromatic adaptation and color constancy. ANSWER: The idea that chromatic adaptation is responsible for color constancy has been tested in an experiment by Keiji Uchikawa and coworkers (1989). Observers viewed isolated patches of colored paper under three different conditions: (a) baseline paper and observer illuminated by white light; (b) observer not adapted-paper illuminated by red light, observer by white (the observer is not chromatically adapted); and (c) observer adapted to red-both paper and observer illuminated by red light (the observer is chromatically adapted). In the baseline condition, a green paper is perceived as green. In the observer not adapted condition, the observer perceives the paper's color as being shifted toward the red. Color constancy does not occur in this condition because the observer is not adapted to the red light that is illuminating the paper. But in the observer adapted to red condition, perception is shifted only slightly to the red, so it appears more yellowish. Thus, the chromatic adaptation has created partial color constancy the perception of the object is shifted after adaptation, but not as much as when there was no adaptation. This means that the eye can adjust its sensitivity to different wavelengths to keep color perception approximately constant as illumination changes. 58. (a) What is the difference between an illumination edge and a reflectance edge? (b) Discuss what the "penumbra" demonstration and the "folded card" demonstration reveal about perception of these types of edges. ANSWER: The perceptual system needs to distinguish between reflectance edges and illumination edges. A reflectance edge is an edge where the reflectance of two surfaces changes, for example, when two surfaces are made of different materials that reflect different amounts of light. An illumination edge is an edge where the lighting changes. Covering the penumbra (the fuzzy border at the edge of the shadow) causes most people to perceive a change in the appearance of the shadowed area. Apparently, the penumbra provides information to the visual system that the dark area next to the cup is a shadow, so the edge between the shadow and the paper is an illumination edge. However, masking off the penumbra eliminates that information, so the area covered by Page 11