Human vision

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Human vision

• Jitendra Malik
• U.C. Berkeley

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Cerebral Cortex
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Monocular Visual Field 160 deg (w) X 175 deg
(h)Binocular Visual Field 200 deg (w) X 135
deg (h)
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Cones and Rods
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Receptor density vs eccentricity
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Processing in the retina
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ON and OFF cells in retinal ganglia
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Visual Processing Areas
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The visual system performs

• Measurement of light and spatial relations
• Perceptual Organization
• Active interaction with environment

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Measurement of light and spatial relations

• Measuring light
• Sensitivity over high dynamic range
• Gain control results in Weber Machine
• Sensitivity to contrast rather than absolute
  luminance leveldiscounting the illuminant
• Measuring Spatial relations
• Contrast sensitivity function
• Vernier Acuity

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Threshold vs. Intensity
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Weber Contrast Cw ?L/LMichelson Contrast CM
(Lmax Lmin)/2 Lmean
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Why contrast is the right variable..
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Simultaneous Contrast
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Mach Band
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A Mach Band in 1D profile
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Craik-OBrien-Cornsweet
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Contrast Sensitivity Function at different
luminances
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Receptor density vs eccentricity
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CSF as function of eccentricity
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Cortical Magnification Factor
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Mapping from Retina to V1
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Physiological Optics 1840-1894
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The Empiricist-Nativist debate
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The debate..(and sometimes both were right !)

• Helmholtz argued that perception is unconscious
  inference. Associations are earned through
  experience.
• Hering proposed physiological mechanismsopponent
  color channels, contrast mechanisms, conjunctive
  and sisjunctive eye movements..

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The Twentieth Century..

• The Gestalt movement emphasized perceptual
  organization.
• Grouping
• Figure/ground
• Configuration effects on perception of brightness
  and lightness

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Grouping factors
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Grouping Factors
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The Figure-Ground Problem
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Transparency
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Wallachs Brightness ratios
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Gibsons ecological optics (1950)

• Emphasized richness of information about shape
  and surface layout available to a moving observer
• Optical flow
• Texture Gradients
• ( and the classical cues such as stereopsis etc)

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Measuring Surface Orientation
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Accomodation
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Depth of field of human eye
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Convergence
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Convergence angle vs. distance
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Binocular Stereopsis
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Optical flow for a pilot
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Some Pictorial Cues
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Shading
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Cast Shadows
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Geometry of cast shadows