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Vision: Subjective and Objective Issues. Oleh Tretiak Medical Imaging Systems 2002. Why Study Vision. Understand how to display images Understand what is seen Understand how vision works. Sources of Information. Physics of vision Neurophysiology of vision Psychology of vision

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vision subjective and objective issues

Vision: Subjective and Objective Issues

Oleh Tretiak

Medical Imaging Systems

2002

why study vision
Why Study Vision
  • Understand how to display images
  • Understand what is seen
  • Understand how vision works
sources of information
Sources of Information
  • Physics of vision
  • Neurophysiology of vision
  • Psychology of vision
  • Psychophysics
references
References
  • David Hubel, Eye, Brain, and Vision, Henry Hold & Company, 1995
  • James P. C. Southall, Physiological Optics, Dover, 1961
  • Vicki Bruce, Patrick R. Green, Mark A. Georgeson, Visual Perception: Physiology, Psychology, and Ecology, Psychology Press, 1996
slide17

The model is due to Gullstrand (1924). The power of the eye in this model ranges from 58.64 dptr (diopters) to 70.57 dptr. Most of the refraction (43 dptr) is due to the cornea.

subjective intensity contrast models
Subjective Intensity (Contrast) Models
  • In a model for subjective intensity, let x by the brightness (power/area) and y the subjective brightness (contrast). Both x and y range from 0 to 100.
  • Logarithmic model:
  • Power law model:
  • On the next slide we show thirty four steps designed to produce uniform contrast with (1) linear, power law with gamma = 1, (2) power law, gamma = 0.7, and (3) logarithmic. Note that the appearance of this depends on the transfer function of the display.
simultaneous contrast examples
Simultaneous Contrast Examples

Background = 245, circles = 210, 225, and 235

Background = 70, circle = 60

slide28

Mach Bands

Subjective (perceived) value

Objective value (intensity)

boundaries
Boundaries

Texture

Brightness