vision part 2
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Vision Part 2. Theories on processing colors. Objectives: The Student Will. Compare and contrast color theories ( VENN ) Explain the Gestalt Theory List your Depth and Distance “cues” What is visual consistency ?. chapter 6. Sensation and perception. How do we see color?. - PowerPoint PPT PresentationTRANSCRIPT
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Vision Part 2
Theories on processing colors
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Objectives: The Student Will
• Compare and contrast color theories (VENN)• Explain the Gestalt Theory• List your Depth and Distance “cues”• What is visual consistency?
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Sensation and perception
chapter 6
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How do we see color?
• Trichromatic theory- theory of color perception Red, green, blue.
• Pattern firing of 3 color receptors• Processes initial stages in the cone cells • Happens in retina, combination theory• cones in retina absent or malfunction= color
blind
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OTOH
• Opponent-process theory- Explains some color blindness and Negative Afterimages
• Electromagnetic Energy= short wavelengths• Happens in ganglion cells, thalamus, visual
cortex• Opponent process cells; cancel colors out
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Trichromatic theoryYoung (1802) and von Helmholtz (1852) both proposed that the eye detects 3 primary colorsRed, blue, and green
All other colors derived by combination
chapter 6
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Opponent-process theory
A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonisticOpponent-process cells are inhibited by a color, and have a burst of activity when it is removed.
chapter 6
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Form perceptionGestalt principles describe the brain’s organization of sensory building blocks into meaningful units and patterns.
chapter 6
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Gestalt Theory
• Perceptual tricks: Blinking lights on Marquee • Gestalt Theory= Patterns in the brain• Gestalt means perceptual pattern or
configuration in German.• Raw material of stimulation is sum of sensory
parts• EQUATION
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Gestalt principlesProximityThings close to one another are grouped together
ClosureThe brain tends to fill in gaps to perceive complete forms
chapter 6
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2 principals
• Proximity- Group things that are near each other
• F.E. 3 groups of red dots not 12 individual dots or Blue vertical columns not horizontal rows
• Closure: Makes you see incomplete figures as wholes by supplying the missing elements.
• None of pictures complete
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Gestalt principlesSimilarityThings that are alike are perceived together
ContinuitySeeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction.
chapter 6
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2 more Gestalt principals
• Similarity- Group together things that have a similar look.
• circles form X; See Horizontal stars because outlined or red
• Continuity- we prefer smoothly connected and continuous figures to disjointed ones
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Your turnWhich Gestalt principle is illustrated by the fact that we see columns of dots rather than rows in this diagram?1. Similarity2. Proximity3. Closure4. Continuity
chapter 6
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Your turnWhich Gestalt principle is illustrated by the fact that we see columns of dots rather than rows in this diagram?1. Similarity2. Proximity3. Closure4. Continuity
chapter 6
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Depth and Distance Perception
• Binocular convergence(need both eyes): How the lines of vision from each eye converge at different angles on objects at different distances
• Put finger 6 in from face, move finger 1 foot back. Feel anything?
• Binocular disparity: Different perspectives in each eye= different in retina either side
• Finger 12 in. from face, alternate eyes• Gives us depth information
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Depth and distance perception
Binocular cues: visual cues that require the use of both eyes
ConvergenceTurning inward of the eyes, which occurs when they focus on a nearby object
Retinal disparityThe slight difference in lateral separation between two objects as seen by the right and left eyes
chapter 6
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Monocular Cues= 1 eye only
• Relative size: objects in mirror closer than appear• Light and shadow: Bright=Closer; Dim=farther away• USED BY ARTISTS • Relative motion: Watch poles from car window,
closer object the faster it seems to move• Interposition: Book obscures the background, stop
sign in front if a car... Perceived as closer• Atmospheric perspective: haze or fog makes
buildings look farther away
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Depth and distance perception
Monocular cues: visual cues that can be used by one eye
chapter 6
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Visual constanciesThe accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produceShape constancyLocation constancySize constancyBrightness constancyColor constancy
chapter 6
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But apple red in kitchen and outside?
• Part sensory adaptation• Adapt to bluish outside (short wave)• Indoors long wave length• Brain takes into account all wavelengths in
visual field
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Visual illusions
• Lines same length- Branches are perspective cues that suggest depth
• A. 1889, German sociologist• B. one is like a near end of a building, other
like far corner of room• Because if same size on retinal image, farther
one away, farther one is larger one• Misinterprets information.
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The Müller-Lyer illusion
chapter 6
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Fooling the eyeThe cats in (a) are the same size.The diagonal lines in (b) are parallel.You can create a “floating fingertip frankfurter” by holding hands as shown, 5–10 inches in front of face.
chapter 6
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Summary
• Color theories • Gestalt• Visual consistencies