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Effect of Test Patch Location on Color Appearance, in the Context of 3D Objects Bei Xiao and David H.Brainard University of Pennsylvania
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What Color is the Mug?
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Most Appearance Studies Consider Flat Uniform Patches
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Highlight Inter-reflection A Complex Pattern of Light is Reflected from 3D Objects
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Surface Gloss Increases the Variation of Reflected Light
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How do people perceive the color of different parts of an object? Questions How do material properties of the object affect color perception?
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Task: Asymmetric Color Matching TestMatch
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Task: Asymmetric Color Matching Adjusting! TestMatch
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Task: Asymmetric Color Matching Adjusting! TestMatch
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Task: Asymmetric Color Matching Adjusting! TestMatch
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Task: Asymmetric Color Matching Adjusting! TestMatch
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Task: Asymmetric Color Matching Adjusting! TestMatch
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Task: Asymmetric Color Matching TestMatch Done!
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Rendering Methods Images are rendered wavelength by wavelength using customized Matlab software (RenderToolbox). The underlying renderer is Radiance. RenderToolbox is available at www.rendertoolbox.org.
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Ward Model of Surface Reflection Specular Component (material properties) Diffuse Component (body color)
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Experimental Variables: Location, Material, Color Material Color Location
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Results: Pictorial Representation Mean Up Match Up Mean Bottom Match Bottom Test Up Test Bottom
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Results: Pictorial Representation Match Up Match Bottom Test Up Mean Up Test Bottom Mean Bottom
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Results: Pictorial Representation Test Up Mean Up Match Up Test Bottom Mean Bottom Match Bottom
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Results: Pictorial Representation Test Up Mean Up Match Up Test Bottom Mean Bottom
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Match Bottom Results: Pictorial Representation Test Up Mean Up Match Up Test Bottom Mean Bottom
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Match Bottom Results: Pictorial Representation Test Up Mean Up Match Up Test Bottom Mean Bottom
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Preliminary Conclusions Changing test patch location of an object has a small effect on color perception of the patch. This is not predicted by the average of the light reflected from the patch. Effect of surface material properties on color perception of the patch is also small.
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Quantitative Data Representation test mean Xiao, B. and Brainard, D.H. (under review) Visual Neuroscience
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Transformed Data Representation test mean
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Transformed Data Representation test mean match
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Transformed Data Representation test mean match
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Transformed Data Representation test mean match
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Transformed Data Representation test mean match
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Transformed Data Representation test mean match
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Soccer Ball Experiment, More Data
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Location Effect Index (LEI) up bottom Vt Vm For each material condition: LEI = [ |Vm| / |Vt| ] test mean match
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LEI Histograms Corrected mean: Purple = 0.09 Yellow-green = 0.13
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Material Influence Index (MII) For each mach: MII = [ |Vm| / |Vt| ] matte glossy test mean match Vt Vm
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MII Histograms Corrected mean: Purple = 0.17 Yellow-green = 0.13
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Conclusions Effect of location is small in comparison with the mean prediction. This suggests color appearance is stable across different parts of an object. Matches are not predicted by the average of the light reflected across the image of the object. Were interested in the color appearance of 3D objects in rich scenes. Surface gloss has a small effect on color perception of the test patch on 3D objects when the diffuse component is constant.
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Prof. David H. Brainard Ah Rim Shin Lu Yin Dan Lichtman Dr. Sarah Allred Prof. James Hillis Dr. Robyn Oliver Chris Broussard Acknowledgement
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Implications For Models Image-statistics: Use image mean, skewness, percentiles to estimate diffuse reflectance (body color). Inverse-optics: estimating geometry of the light source and use the estimated geometry to infer diffuse reflectance.
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Design: Test Patch Location Effect
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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CIELAB Representation of Test Stimuli
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LEI Histograms, Compared with Residuals
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Material Influence Index (LEI)
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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Results: Pictorial Representation Test Up Match Up Mean Up Test Bottom Match Bottom Mean Bottom
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