Human Visual Systems and PerceptionHuman Visual Systems and PerceptionHuman Visual Systems and PerceptionHuman Visual Systems and Perception

C. Edward C. Edward ChowChowC. Edward C. Edward ChowChow

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Image in Human EyeImage in Human EyeImage in Human EyeImage in Human Eye

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Rod and Cone Cell Rod and Cone Cell DistributionDistributionRod and Cone Cell Rod and Cone Cell DistributionDistribution

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Contrast Illusion Contrast Illusion Contrast Illusion Contrast Illusion

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Demystify Illusion with Mach Bend Demystify Illusion with Mach Bend

EffectEffect Demystify Illusion with Mach Bend Demystify Illusion with Mach Bend

EffectEffect

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Spatial FrequenciesSpatial FrequenciesSpatial FrequenciesSpatial FrequenciesImage can be considered as Image can be considered as superposition of gratings of different superposition of gratings of different spatial frequencies (cycles/degree).spatial frequencies (cycles/degree).

Image can be considered as Image can be considered as superposition of gratings of different superposition of gratings of different spatial frequencies (cycles/degree).spatial frequencies (cycles/degree).

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Contrast ImpactContrast ImpactContrast ImpactContrast Impact

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Visual AcuityVisual AcuityVisual AcuityVisual Acuity

Visual acuity: the Visual acuity: the smallest angular smallest angular separation at separation at which the which the individual lines individual lines can be can be distinguished. distinguished.

Depend on Depend on contrast ratio and contrast ratio and keenness of your keenness of your eyes. 1.7’ is eyes. 1.7’ is normal normal assumption= assumption= 60/(2*1.7’)~18 60/(2*1.7’)~18 cycles/degreecycles/degree

Visual acuity: the Visual acuity: the smallest angular smallest angular separation at separation at which the which the individual lines individual lines can be can be distinguished. distinguished.

Depend on Depend on contrast ratio and contrast ratio and keenness of your keenness of your eyes. 1.7’ is eyes. 1.7’ is normal normal assumption= assumption= 60/(2*1.7’)~18 60/(2*1.7’)~18 cycles/degreecycles/degree

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Color RepresentationColor RepresentationThree-Receptor ModelThree-Receptor ModelColor RepresentationColor RepresentationThree-Receptor ModelThree-Receptor Model

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Perception RepresentationPerception RepresentationPerception RepresentationPerception Representation

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Tristimulus CurvesTristimulus CurvesTristimulus CurvesTristimulus CurvesDevise a system with simple numbers Devise a system with simple numbers to represents all colors. (How about to represents all colors. (How about all positive numbers?)all positive numbers?)

x,y,z are proportion of X primary, Y x,y,z are proportion of X primary, Y primary, Z primary (supersaturated primary, Z primary (supersaturated red, green and blue)red, green and blue)

x=X/(X+Y+Z); y=Y /(X+Y+Z); z=1-x-x=X/(X+Y+Z); y=Y /(X+Y+Z); z=1-x-yy

Devise a system with simple numbers Devise a system with simple numbers to represents all colors. (How about to represents all colors. (How about all positive numbers?)all positive numbers?)

x,y,z are proportion of X primary, Y x,y,z are proportion of X primary, Y primary, Z primary (supersaturated primary, Z primary (supersaturated red, green and blue)red, green and blue)

x=X/(X+Y+Z); y=Y /(X+Y+Z); z=1-x-x=X/(X+Y+Z); y=Y /(X+Y+Z); z=1-x-yy

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CIE {X,Y,Z} systemCIE {X,Y,Z} systemCIE {X,Y,Z} systemCIE {X,Y,Z} system

CIE: Commission Internationale de I’Eclairage, The CIE: Commission Internationale de I’Eclairage, The International commission on color standards)International commission on color standards)

Figure 2.17b shows the corresponding amount of Figure 2.17b shows the corresponding amount of primaries needed to match all wavelengths of primaries needed to match all wavelengths of visible spectrum.visible spectrum.

CIE: Commission Internationale de I’Eclairage, The CIE: Commission Internationale de I’Eclairage, The International commission on color standards)International commission on color standards)

Figure 2.17b shows the corresponding amount of Figure 2.17b shows the corresponding amount of primaries needed to match all wavelengths of primaries needed to match all wavelengths of visible spectrum.visible spectrum.

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1931 CIE Chromaticity Diagram1931 CIE Chromaticity Diagram1931 CIE Chromaticity Diagram1931 CIE Chromaticity Diagram

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Color Coordinate System ConversionColor Coordinate System ConversionColor Coordinate System ConversionColor Coordinate System Conversion

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Transformation from NTSCTransformation from NTSCTransformation from NTSCTransformation from NTSC