EEE508_LuminanceBrightnessCSFColorVision

EEE508_LuminanceBrightnessCSFColorVision - Lateral...

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Lateral Inhibition Lateral Inhibition Copyright 2010 by Lina J. Karam
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Lateral Inhibition Mach Band Effect Copyright 2010 by Lina J. Karam
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Lateral Inhibition Lateral Inhibition Mach Band Effect Ͳ Luminance versus brightness Luminance aylevel Brightness Distance Gr Copyright 2010 by Lina J. Karam
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Lateral Inhibition Simultaneous Contrast ± Luminance versus Brightness All the center squares have the same intensity. Copyright 2010 by Lina J. Karam
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Luminance and Brightness: Contrast Sensitivity Contrast sensitivity experiment L L + ' L The smallest ' L for which dot is visible is the just Ͳ noticeable difference (JND) or detection threshold. Ct t iti it il ti l t JND ' Contrast sensitivity inversely proportional to JND L Weber±s law: ' L / L = constant (~0.01) Equal increments in log L should be perceived to be equally different: linear relation between Brightness B and log of luminance Log relation between Brightness B and Luminance L Copyright 2010 by Lina J. Karam approximated by a power function
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Luminance and Brightness: Contrast Sensitivity Relation between Brightness and Luminance 4 . 0 L B B 1.0 0.8 0.6 0.4 0.2 L 0.2 1.0 0.4 0.6 0.8 Copyright 2010 by Lina J. Karam
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Luminance and Brightness: Contrast Sensitivity Contrast sensitivity experiment Variability between subjects result in L different JND value per subject Psychometric function: probability L + ' L of detection for a background illumination L x Probability of Detection, P E ) | / | ( ) | / | ( 2 1 1 JND JND L L L L P e P ' ' ± ' ' ± ± ± x ' ' Copyright 2010 by Lina J. Karam L L JND
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Contrast Sensitivity Contrast sensitivity experiment: sinusoidal grating over flat L E background of constant luminance L + ' L L is mean luminance of sinusoidal grating and background ' is amplitude of sinusoidal grating is orientation of sinusoidal grating The smallest contrast ' L for which sinusoid is visible is the just Ͳ noticeable difference (JND) or contrast sensitivity detection threshold at the considered sinusoid±s frequency and orientation The JND varies with the spatial and angular (orientation) frequencies of the sinusoidal grating for a given background luminance L . Copyright 2010 by Lina J. Karam
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Contrast Sensitivity Visual acuity: ability to detect spatial details Contrast Sensitivity (spatial): how visual acuity changes with spatial frequency and orientation for a given surrounding luminance Copyright 2010 by Lina J. Karam
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Contrast Sensitivity Visual acuity: ability to detect spatial details Contrast Sensitivity (spatial): how visual acuity changes with spatial frequency and orientation for a given surrounding constant luminance Copyright 2010 by Lina J. Karam
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Contrast Sensitivit Contrast Sensitivity Spatial frequency is not related to the wavelength of the light is the number of oscillations in a given space 0 o 10 o 30 o 1 o 10 o 30 o 0 o 4 cycles/retinal arc 30 o 10 o 0 o 10 o 30 o 0 o 0.5 o 4 cycles/half retinal arc 8 l/t il Copyright 2010 by Lina J. Karam = 8 cycles/retinal arc
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Contrast Sensitivity
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This document was uploaded on 03/11/2012.

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EEE508_LuminanceBrightnessCSFColorVision - Lateral...

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