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CS 450: Human Vision includes about Discrimination Experiments, Weber’s Law, Weber’s Law and Logarithmic Encoding, Adaptation, Contrast Encoding, Spatial Frequencies, Color Perception, Brightness vs. Color. | CS 450 Human Vision 1 Human Vision I Some properties of human vision that affect image perception Linear and non-linear parts Nonlinear approx. logarithmic encoding of input Adaptation Relative-contrast encoding Varying sensitivity to spatial frequecies Generally treats brightness and color separately CS 450 Human Vision 2 Discrimination Experiments Many vision experiments involve comparisons. Two alternative forced choice experiments is it there yes no which is brighter farther apart etc. top bottom left right etc. Random guessing without bias 50 correct Pick some percentage above which the the observer must get it right often 75 half the time they see it half the time they guess . Vary the experimental parameter to determine the threshold T above which the observer reaches this desired level of confidence. This is called the just noticable difference j.n.d. . Sensitivity 1 T CS 450 Human Vision 3 Weber s Law Many visual properties obey Weber s law. For intensity discrimination AI I c for some constant c. In other words the j.n.d. AI for intensity is proportional to the intensity itself. Also applies to distance judgements spatial frequency discrimination and many .