Shimamura_Chp+2

Shimamura_Chp+2 - Chapter 2 Act I: The Art of Seeing...

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Chapter 2 22 Act I: The Art of Seeing Chapter 2. The Eye as Canvas, the Brain as Beholder Consider the landscape painting, Twilight in the Wilderness, by the American painter Fre- deric Church (Figure 2.1). One can imagine standing at cliff’s edge admiring this river valley at sunset. In fact, there is much in common in the way we interpret a painting and how we perceive an actual scene. Both begin with an image: one created by an artist on canvas and the other projected onto our retina by nature. It is re- markable that from our mi- niscule retinal canvas, we are able to perceive the space around us and, more importantly, move through it with extraordinary ease. The critical feature of both art and perception is the manner in which light is rendered onto a surface. Artists are well attuned to the nature of light and how surfaces reflect different patterns and shadings. It is the brain, as be- holder, that interprets these crazily moving patterns of light to give us a 3-D representation of the world around us. Camera Obscura Find a soda can and cut it in half around the middle. In the center of the bottom half, make a tiny pinhole puncture using a small nail and hammer. Cut a piece of a white plastic grocery bag (or some other translucent sheet), and place it over the opening securing it tightly with black electrical tape. Use the tape to re-attach the two halves together making sure that light can’t seep into the sides. Now point the pinhole toward a sunny scene and look inside the can from the top opening. You should see a dim upside-down image of the outside world projected onto the sheet (Footnote 2.1). You have just built a camera obscura (Latin for dark chamber). De- scriptions of such devices were made as early as the 4 th and 5 th Century B.C. by Aristotle and the Chinese philosopher, Mo Jing. By the 17 th century, sophisticated versions were built as artist’s aids. As shown in Figure 2.2, some were small tabletop viewers, while others were room-sized chambers in which the artist entered and traced images projected onto a surface. Even today, at tourists sites from
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Chapter 2 23 Edinburgh to San Francisco, you can visit a room-sized camera obscura and view the outside world on a screen, as if you are watching a movie. Seeing Light If you made the hole in your camera obscura slightly larger and placed lenses near the opening, you would have the makings of a camera and a model of the general optics of the eye. Both camera and eye start with a small opening at the front, the aperture for a camera and the pupil for the eye. These openings are adjustable, allowing more or less light into the chamber. Lenses help focus the image onto the back surface and increase brightness in the chamber. In the eye, the cornea , the round lens at the front of the eye, contributes to most of the eye’s focusing power. A second focusing lens, called the lens , is situated behind the cornea and is used for fine tuning as its curvature is adjustable by tiny muscles around it. Through these optics, light rays invert so that the image projected is upside-down and re-
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This note was uploaded on 11/04/2010 for the course PSYCH 39E SEM taught by Professor Shimamura during the Spring '10 term at Berkeley.

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Shimamura_Chp+2 - Chapter 2 Act I: The Art of Seeing...

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