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Optical Illusions Christopher Landauer Science of Art March 9, 2000 What is an Illusion? il·lu·sion (-lzhen) noun 1. a. An erroneous perception of reality. b. An erroneous concept or belief. 2. The condition of being deceived by a false perception or belief. 3. Something, such as a fantastic plan or desire, that causes an erroneous belief or perception. 4. Illusionism in art. • Latin root of illusion is illudere which means “to mock” • Optical illusions mock our trust in our senses • Suggest that the eye is not a passive camera; rather, perception is an active process that takes place in the brain and is not directly predictable from simple knowledge of physical relationships What’s the big deal? • Human reliance on correspondence between conscious experience and physical reality • Continual verification of our senses • Cultural Heritage – “Seeing is Believing” – “See it with my own two eyes” History of Illusions Prehistory: • Afterimage caused by glancing at the sun • A stick half in and half out of water History of Illusions 500 B.C. - Height of the Greek Period “The eyes and ears are bad witnesses when they are at the service of minds that do not understand their language” -Parmenides Two Viewpoints on Perception: 1. Sensory inputs are inaccurate. Mind corrects these inaccuracies to provide an accurate representation of the environment. Illusions: Senses are relied on more than the Mind 2. Senses are inherently accurate and produce a true picture of the environment. Mind is limited. Illusions: Mind interferes with the Senses History of Illusions c. 450 B.C. “The mind sees and the mind hears. The rest is blind and deaf.” -Epicharmus “Man is nothing but a bundle of sensations” -Protagoras c. 300 B.C. “We must perceive objects through the senses but with the mind” -Plato 384 - 322 B.C. “Each sense has one kind of object which it discerns, and never errs in reporting that what is before it is color or sound; Although, it may err as to what it is that is colored or where it is, or what it is that is sounding, or where it is.” -Aristotle History of Illusions A. Ideal Parthenon B. Architrave Illusion (Jastrow-Lipps) C. Illusionary Distortion D. Alterations made to offset illusion History of Illusions “For the sight follows gracious contours; and unless we flatter its pleasure by proportionate alterations of the modules--so that by adjustment there is added the amount to which suffers illusion--an uncouth and ungracious aspect will be presented to the spectators.” -Vitruvius History of Illusions Entasis: Convexing of column to overcome parallel lines appearing concave Irradiation Illusion: Bright objects appear larger History of Illusions Conclusion: “More of an Art than a Science” Early Preparadaigmatic Science -Trial and error -Aesthetic, not scientific -No factual understanding -No treatsies -No schools of thought History of Illusions 1596 - 1650 Descartes: There is both a registration stage and an interpretation stage in the perceptual process. Perceptual error or illusion may intrude at either of these two steps along the road to consciousness. 1700 - 1800 Given at Birth vs. Learned through Experience Reid & Kant: All knowledge of the external world comes directly through the senses and is interpreted by innate mechanisms Berkeley & Hume: All perceptual qualities are learned through experience with the environment History of Illusions 1800 - 1870 Experimental Foundations Mueller, E.H. Weber, Helmholtz, Baldwin, Hering use Physics, Physiology, Philosophy to form treatises Specialist and Non-specialist working in area of visual geometric illusions carrys on to the present 1922 - Luckiesh: lighting engineer 1964 - Tolansky: physicist 1972 - Robinson: psychologist 1900s Revolution and Rebirth • Behaviorists vs. Gestalt • Methodology vs. Theoretical • Percepual response & Brain wave patterns Current State of Illisions Conclusion: Paradigmatic Science (Psychology) 1900s Normal Sciences => Anomoly => Crisis => Revolution Current status: Normal Science - mopping up - puzzle solving - guidelines for research Ambiguous Figures Face or Vase? Ambiguous Figures RetroActive Nels Isralson L'Amour de Pierrot c.1905 Gossip and Satan Geo. A. Wotherspoon Ambiguous Figures Bust of Voltaire - Houdon, 1781 Slave Market With the Disappearing Bust of Voltaire - Salvadore Dali, 1940 Ambiguous Figures The Great Panoramic - Salvadore Dali, 1936 Ambiguous Figures Multiple Figures 2 3 2 2 Ambiguous Figures Mask Concavity Ambiguous Figures Mach’s Figure Ambiguous Figures Schroder’s Staircase Ambiguous Figures Oscillating Cubes Ambiguous Figures Necker Cube Ambiguous Figures Ambiguous Figures Cube looks like a cube. “Equal sides and right angles.” Eye: Perspetive projection Reverse: Topless pyramid change of shape Cube looks distorted, on face smaller than the other. Depth is paradoxical Reverse: No Change Ambiguous Figures Cube does not look like a cube. Eye: Near face is same size as far face Reverse: Topless pyramid further face always looks larger Necker Cube. No face is front or back by perspective Depth is paradoxical Reverse: No change Ambiguous Figures Possible views: • Cube with corner missing • Box in corner of room • Small cube infront of large cube 3 in 1 Illusion Ambiguous Figures Cube / Room Possible views: • 3D Cube • Corner of Room