4 Main Types of Visual Information Processing

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4 Main Types of Visual Information Processing

• Luminance Contrast
• Colour
• Motion
• Depth

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Spatial Vision and Pattern Perception

• scale as spatial frequency
• spatial frequency analysis and the MTF
• physiological responses to gratings and the CSF
• perceptual consequences of spatial frequency
  analysis
• feature detectors vs. ensemble encoding

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Scale as Spatial Frequency

• "scale"
• big picture info - skyline
• medium - buildings
• details - windows
• different receptive field sizes process
  information on different scales

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Spatial Vision and Pattern Perception

• scale as spatial frequency
• spatial frequency analysis and the MTF
• physiological responses to gratings and the CSF
• perceptual consequences of spatial frequency
  analysis
• feature detectors vs. ensemble encoding

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Spatial Frequency Analysis

• amplitude
• height of wave form
• luminance modulation --gt grating
• frequency
• number of light and dark bars per degree of
  visual angle
• "scale" spatial frequency
• big picture info low spatial frequency
• details high spatial frequency
• (if SF too high gray patch)

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Spatial Frequency Analysis

• amplitude
• frequency
• orientation
• phase

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Fourier Analysis

• can be used to describe all patterns
• a way of analyzing complex wave forms into a
  series of sine waves
• compound gratings
• square wave grating from sine wave gratings
• blurring is like removing the high frequency
  components
• can make any 2D pattern by manipulating
  amplitude, frequency, phase and orientation of
  sine wave gratings

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Modulation Transfer Function

• limitations of optical system
• high frequency details lost

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Spatial Vision and Pattern Perception

• scale as spatial frequency
• spatial frequency analysis and the MTF
• physiological responses to gratings and the CSF
• perceptual consequences of spatial frequency
  analysis
• feature detectors vs. ensemble encoding

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Physiological responses to gratings

• modulation transfer function (MTF)
• contrast sensitivity function (CSF) is MTF of
  visual system
• CSF as a spatial frequency filter

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Contrast sensitivity function

• How do we measure the quality of the image
  produced by the human visual system?
• The perceptual transfer function depends on the
  optical transfer function and the neural transfer
  function

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Multiple Channel Model (Campbell Robson)

• suggested a set of spatial frequency channels
• each set tuned to a different range of spatial
  frequencies

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Spatial Vision and Pattern Perception

• scale as spatial frequency
• spatial frequency analysis and the MTF
• physiological responses to gratings and the CSF
• perceptual consequences of spatial frequency
  analysis
• feature detectors vs. ensemble encoding

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Perceptual Consequences Related to Spatial
Frequency Analysis

• "size aftereffect"
• adaptation of spatial frequency channels
• high frequency masking

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High Frequency Masking
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Spatial Vision and Pattern Perception

• scale as spatial frequency
• spatial frequency analysis and the MTF
• physiological responses to gratings and the CSF
• perceptual consequences of spatial frequency
  analysis
• feature detectors vs. ensemble encoding

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Feature Detectors vs. Ensemble Coding

• feature detectors grandmother neuron
• ensemble coding pattern of activity