viewing the world in color
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VIEWING THE WORLD IN COLOR. COLOR. A psychological interpretation Based on wavelength, amplitude, and purity Humans can discriminate among c. 10 million colors Variations are a result of mixing…. COLOR. - PowerPoint PPT PresentationTRANSCRIPT
VIEWING THE WORLD IN COLOR
COLOR• A psychological
interpretation• Based on
wavelength, amplitude, and purity• Humans can
discriminate among c. 10 million colors• Variations are a
result of mixing…
COLOR• Subtractive mixing:
removing some wavelengths of light, leaving less light than was originally there• Additive color:
superimposing lights, putting more light in the mixture than exists in any one light itself
TRICHROMATIC THEORY OF COLOR VISION• Holds that the
human eye has 3 types of receptors with differing sensitivities to different light wavelengths• Helmholtz: red,
green, and blue---the primary colors
COLOR BLINDNESS• Encompasses a
variety of deficiencies in the ability to distinguish among colors• More frequent in
males• Most are dichromats
OPPONENT PROCESS THEORY OF COLOR VISION• Holds that color
perception depends on receptors that make antagonistic responses to 3 pairs of colors• Complementary colors:
colors that produce gray tones when mixed together• Afterimage: a visual
image that persists after a stimulus is removed
RECONCILING THEORIES OF COLOR VISION
• It takes both theories to explain color vision• George Wald: eye has 3
types of cones---trichromatic theory• DeValois: cells
throughout the eye respond in opposite ways to red vs. green and blue vs. yellow---opponent process
PERCEIVING FORMS, PATTERNS, AND OBJECTS• Reversible figure: a
drawing that is compatible w/2 interpretations that can shift back and forth
• Demonstrates same visual input can result in radically different perceptions
• Perceptual set: a readiness to perceive a stimulus in a particular way
FEATURE ANALYSIS• The process of
detecting specific elements in visual input and assembling them into a more complex form
BOTTOM-UP/TOP-DOWN• Bottom-up
processing: a progression from individual elements to the whole• Top-down processing:
a progression from the whole to the elements
LOOKING AT THE WHOLE: GESTALT PRINCIPLES
• The whole can be more than the sum of its parts• Phi phenomenon: the
illusion of movement created by presenting visual stimuli in rapid succession
GESTALT PRINCIPLES• Figure and ground:
figure is thing being looked at and ground is the background• Figures have more
substance and shape, and appear closer
GESTALT PRINCIPLES• Proximity: things near one
another seem to belong together• Similarity: we group things
that are similar• Continuity: tendency to
follow the direction you are led• Simplicity: organize in
simplest way possible• Closure: group in order to
create completeness
FORMULATING PERCEPTUAL HYPOTHESES• Distal stimuli: stimuli that
lie in the distance (outside the body)• Proximal stimuli: the
stimulus energies that impinge directly on sensory receptors• Perceptual hypothesis: an
inference about which distal stimuli could be responsible for the proximal stimuli sensed
PERCEIVING DEPTH AND DISTANCE
• Depth perception: interpretation of visual cues that indicate how near or far away objects are• We rely on different
clues classified in 2 types…
BINOCULAR CUES• Def: clues about distance based on the differing views of the 2
eyes• Principle depth cue is retinal disparity: the fact that objects
within 25 ft project images to slightly different locations on the right and left retinas, so the right and left eyes see slightly different views of the object
• Another cue is convergence: sensing the eyes converging toward each other as they focus on closer objects
MONOCULAR CUES• Def: clues about
distance based on the image in either eye alone• Motion parallax:
images of objects at different distances moving across the retina at different rates
MONOCULAR CUES• Pictorial depth cues:
clues about distance that can be given in a flat picture• Includes linear
perspective, texture gradients, interposition, relative size, height in plane, and light and shadow
PERCEPTUAL CONSTANCIES IN VISION• Perceptual
constancy: a tendency to experience a stable perception in the face of continually changing sensory input
OPTICAL ILLUSIONS• Def: an apparently
inexplicable discrepancy btwn the appearance of a visual stimulus and its physical reality• Müller-Lyer Illusion• Ponzo Illusion• Shepard Illusion• Ames Room
IMPOSSIBLE FIGURES• Def: objects that can
be represented in 2 dimensional pictures but cannot exist in 3 dimensional space