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Understanding Optical Illusions Mohit Gupta
Truth: But this is an ! What are optical illusions? Light (Sensing) Oracle Perception: I see
Optical Illusion in Nature Image Courtesy:
A Brightness Illusion
Different kinds of illusions Brightness and Contrast Illusions Twisted Cord Illusions Color Illusions Perspective Illusions Relative Motion Illusions Illusions of Expressions
Lightness Constancy Our Vision System tries to compensate for differences in illumination
Why study optical illusions? Studying how brain is fooled teaches us how it works It makes us happy : Al Seckel Illusions of the senses tell us the truth about perception [Purkinje]
Simultaneous Contrast Illusions
Low-level Vision Explanation Receptive Fields in the Retina Negative Photo-receptors Positive Photo-receptors Inhibitory Light Excitatory Light
Low-level Vision Explanation Positive Gradient Negative Gradient
High-level Vision Explanation: Context Less Incident Illumination More Incident Illumination Brightness = Reflectance * Incident Illumination Higher Perceived Reflectance Lower Perceived Reflectance
The Hermann grid illusion
The Hermann grid: Low level Explanation Lateral Inhibition
The Hermann grid illusion Focus on one intersection
Why does the illusion disappear? Receptive fields are smaller near the fovea (center) of the eye
The Waved Grid: No illusion!
Scintillating Grids: Straight and Curved
Adelsons checkerboard illusion
Where is the illusion?
Rubiks Cube Color Illusion Same Color?
Rubiks Cube Color Illusion
Todorovics Gradient Chessboard Illusion Are all the dots the same color?
Craik-OBrien-Cornsweet Illusion Actual Profile Perceived Profile
Footstep Illusion Click Contrast affecting Perception of speed
Twisted Cord Illusions
Are the lines parallel? Straight?
Café Wall Illusion
A variant of the Café Wall Illusion
The Fraser Spiral Illusion
Pinnas Intertwining Illusion
Illusions involving perspective
Shepards table-top illusion Which is bigger?
Shepards table-top illusion Which is bigger?
Shape-from-Shading Shadows influence the perception of shape
Click Kerstens Ball and Shadow Illusion Shadows influence the perception of motion and position
Relative Motion Illusions
Out of Focus Illusion
Spinning Wheel Illusion
Motion Induced Blindness Click
Anamorphoses Leonardos Eye [Leonardo Da Vinci, 1485]
Image Courtsey: Good things come to those who wait
Why study optical illusions? Studying how brain is fooled teaches us how it works It makes us happy : Al Seckel Click Illusions of the senses tell us the truth about perception [Purkinje]
Have fun with Optical Illusions Then think about them! Eschers Waterfall
Mach Band Illusions
Intrinsic Image Separation
Footstep Illusion: Contrast affecting Perception of speed Kick-back Illusion Stepping feet Illusion Reverse-phi phenomenon[Howe et al, Journal of Vision]
Levels of Processing Low-level Vision Mid-level Vision High-level Vision Light receptive cells at the retina level Surfaces, contours, grouping Cognition – knowledge about materials, objects, scenes, illumination
Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F Phone: Lectures: Tuesdays.
Two Views of Perception: Bottom-up processing: -Low-level -Feature driven Top-down processing -Knowledge driven -Unconscious inference (Helmholtz)
Chapter 7: Processing the Image Review structure of the eye Review structure of the retina Review receptive fields –Apply to an image on the retina –Usage.
Exam Results Mean: 76 Median: 79. Exam Results: Grading Policies Our grading policies as outlined on the website are as follows: Approximately half of.
Ch 31 Sensation & Perception Ch. 3: Vision © Takashi Yamauchi (Dept. of Psychology, Texas A&M University) Main topics –convergence –Inhibition, lateral.
1 Georgia Tech, IIC, GVU, 2006 MAGIC Lab Rossignac Perception Human vision limitations Levels of perception
Chapter 3: Neural Processing and Perception. Lateral Inhibition and Perception Experiments with eye of Limulus –Ommatidia allow recordings from a single.
EE465: Introduction to Digital Image Processing1 Waterfall by M.C Escher Image Perception Drawing hands by M.C Escher.
Perception "Colors, tones, smells, and tastes are mental constructions created by the brain out of sensory experience. They do not exist, as such, outside.
Sensation Chapter 5 Myers AP Psychology. Transduction Conversion of one form of energy into another. In sensation, the transforming of stimulus energies,
Version 0.10 (c) 2007 CELEST VISI N Star Light, Star Bright, Let’s Explore Light How You Perceive Light How many black dots can you count?
Perception 1. Inattentional Blindness Challenge: Count the number of passes the white shirts pass! VideoVideo (2mins) Video Type of selective attention.
Perception Notes 6-3 (Obj. 5-11). Depth Perception Visual Cliff Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that.
Outline Sensation, Perception, Behavior Process of sensation Perceived vs. “real” world Properties of perceptual processes - Adaptation, pattern coding.
Chapter 3: Neural Processing and Perception. Neural Processing and Perception Neural processing is the interaction of signals in many neurons.
Gestalt Principles of Perception Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/08 /2015: Lecture 02-3 This Powerpoint presentation.
Optical Illusions What the Mind Sees. Optical Illusions Science Project Type Physiology (eyes, brain) Grade K-5 Difficulty Easy Safety Issues.
COMPUTER GRAPHICS CS 482 – FALL 2015 SEPTEMBER 1, 2015 HUMAN VISUAL PERCEPTION EYE PHYSIOLOGY COLOR BLINDNESS CONSTANCY SHADOWS PARALLAX STEREOSCOPY.
Do we know what the world looks like? The eye is made up of some of the most amazing tissue in the body. The lens, for example, is perfectly clear, perfectly.
Visual Perception and Illusions. Optical Illusions Which of the above gray rectangles is darker?
INTRODUCTION TO PSYCHOLOGY Perception. “Perception refers to the interpretation of what we take in through our senses. In terms of optical illusions this.
1 Perception, Illusion and VR HNRS 299, Spring 2008 Lecture 8 Seeing Depth.
PERCEPTUAL ORGANIZATION. When we are given a cluster of sensations, we organize them into a “gestalt” or a “whole” “The whole is greater than the.
1 Perception and VR MONT 104S, Fall 2008 Lecture 8 Seeing Depth.
Chapter 6 Section 2: Vision. What we See Stimulus is light –Visible light comes from sun, stars, light bulbs, & is reflected off objects –Travels in the.
Image Perception ‘Let there be light! ‘. “Let there be light”
Sensation and Perception Module 19 Visual Organization and Interpretation.
PSYCH 2220 Sensation & Perception I Lecture 3. Keywords for lecture 2 Air-dwelling eye, water-dwelling eye, (both: mask, powerful lens, flat cornea, pinhole),
QofD 11/14 Name all 5 of your sensory receptors for each of the 5 senses.
Optical Perception What color is the central square on each visible surface ?
Imaging Science FundamentalsChester F. Carlson Center for Imaging Science The Human Eye and Vision 2 (Processing The Image)
Chapter 9: Perceiving Color. Figure 9-1 p200 Figure 9-2 p201.
Perception How we organize and interpret sensory information.
S ENSATION & PERCEPTION Chapter 4. V ISION Wavelength (rue) Amplitude Purity Cornea Lens Iris Pupil Retina -transduction Optic disk Optic nerve Rods Cones.
Some quick revision!. Perception: Visual Illusions.
Lecture 16 – Lightness Perception. Physical Measures of Light Luminous flux – light / unit area / unit time Illumination (illuminance)– light that falls.
Visual structure & Blind spot. Question 1 What do these devices have in common?
Visual Cognition I basic processes. What is perception good for? We often receive incomplete information through our senses. Information can be highly.
Vision Hearing Other Senses Perception 1 Perception 2.
Sensation Vision The Eye Theories Hearing The Ear Theories Other Senses Smell Taste Pain Gestalt Principles Perceptual Constancies Perception Basic Principles.
PSYCHOLOGY, Ninth Edition in Modules David Myers PowerPoint Slides Aneeq Ahmad Henderson State University Worth Publishers, © 2010.
Sensation and Perception The Five Senses Gestalt Perceptions Cues to the brain.
Foveal cones are about 2.4 μm in diameter (0.7 min of arc) Peripheral cones are about 5.8 μm in diameter (1.7 min of arc)
Perception Chapter 3 Light is necessary but not sufficient for vision Ganzfeld: a visual field completely lacking in contour, or luminance changes. Prolonged.
Optical Illusion An optical illusion (also called a visual illusion) is characterized by visualll perceived images that differ from objective reality.
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Perceptual Organization Chapter 6, Lecture 5 “The motion we then see in popular action adventures is not in the film, which merely presents a superfast.
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