Sensitivity to color variations & Spatial Localization Setareh - PDF document

Sensitivity to color variations & Spatial Localization Setareh Rafatirad Behzad Sajadi 1 Outline • Part 1 – Color Spatial Contrast Sensitivity Function – Significance of Color CSFs for Vision • Part 2 – Multiple Color Spatial Frequency Channels – Luminance ‐ Color Interactions • Part 3 – Introduction to Phase and Position – Spatial Localization in Visual System • Part 4 – Physiology of Phase and Position Sensitivity – Some Limitations in the Visual System 2 1

Visual System � Part 1 � Color Spatial CSF • Study of Visual System � Significance of Color CSFs for Vision – Spatial Vision � Part 2 – Color Vision � Multiple Color Spatial Frequency Channels • Field intersections � Luminance ‐ Color Interactions – Variation across both chromaticity � Part 3 and luminance � Introduction to Phase and Position � Spatial • Shadowing Localization in Visual System – Objects in shadow � Part 4 � Physiology of Phase and Position Sensitivity 3 � Some Limitations in the Visual System Wavelength Distribution � Part 1 � Color Spatial CSF � Significance of • Trivial color contrast Color CSFs for Vision � Part 2 • More veridical � Multiple Color Spatial Frequency • More information Channels � Luminance ‐ Color • Low and middle frequency Interactions � Part 3 • Very expensive � Introduction to Phase and Position � Spatial • Birds, insects Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 4 � Some Limitations in the Visual System 2

Intensity Distribution � Part 1 � Color Spatial CSF � Significance of • Non ‐ trivial luminance contrast Color CSFs for Vision � Part 2 • Middle and high frequency � Multiple Color Spatial Frequency • Less veridical Channels � Luminance ‐ Color Interactions • Rapidly changing or moving � Part 3 pattern � Introduction to Phase and Position � Spatial • Ungulates and grass eaters Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 5 � Some Limitations in the Visual System Chromaticity vs. Intensity � Part 1 � Color Spatial CSF � Significance of Color CSFs for Vision � Part 2 � Multiple Color Spatial Frequency Channels � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System Mostly contours Loses most of � Part 4 are recognized the information � Physiology of Phase and Position Sensitivity 6 � Some Limitations in the Visual System 3

Chromaticity vs. Intensity � Part 1 � Color Spatial CSF � Significance of Color CSFs for Vision � Part 2 � Multiple Color Spatial Frequency Channels � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System Mostly contours Loses most of � Part 4 are recognized the information � Physiology of Phase and Position Sensitivity 7 � Some Limitations in the Visual System Color ‐ mixture Grating � Part 1 � Color Spatial CSF � Significance of • Mixing colors � Intermediate colors Color CSFs for Vision � Part 2 • Create an isoluminant red ‐ green grating � Multiple Color – Summing two out ‐ of ‐ phase Spatial Frequency Channels isochromatic luminance gratings ‐ � Luminance ‐ Color Interactions matched in luminance � Part 3 � Introduction to • Red grating (180 ° out ‐ of ‐ phase) + Green Phase and Position grating � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 8 � Some Limitations in the Visual System 4

Color ‐ mixture Grating � Part 1 � Color Spatial CSF � Significance of Result : Color CSFs for Vision � Part 2 Red ‐ Green grating � � Multiple Color Spatial Frequency ‐ The same spatial frequency Channels � Luminance ‐ Color Interactions ‐ Varies sinusoidally (red ‐ green) � Part 3 ‐ Invariant luminance � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 9 � Some Limitations in the Visual System Cone Responses � Part 1 � Color Spatial CSF � Significance of Color CSFs for Vision � Part 2 � Multiple Color Spatial Frequency Channels � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity C,D: Receptor sum: varies with luminance contrast 10 � Some Limitations E,F: Receptor Difference: varies with color contrast in the Visual System 5

Pure Color Gratings � Part 1 � Color Spatial CSF � Significance of Color CSFs for Vision � Part 2 � Multiple Color Spatial Frequency Channels � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in •Isoluminant | Equiluminant Visual System •Chromaticity variation � Part 4 � Physiology of •No variation in luminance or chromaticity along the Phase and Position Sensitivity orthogonal axis 11 � Some Limitations in the Visual System A Phenomenon � Part 1 � Color Spatial CSF • Van der Hoarst, de Weert, and Bouman (1967) � Significance of Color CSFs for • Van der Hoarst and Bouman (1969) Vision � Part 2 • Measures of color sensitivity Experiment: � Multiple Color – Low spatial frequencies Spatial Frequency – High spatial frequencies Channels � Luminance ‐ Color • Peculiar experiment: Luminance Artifacts!!! Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity � Some Limitations 12 in the Visual System 6

Aberration � Part 1 � Color Spatial CSF � Significance of • Axial chromatic aberration Color CSFs for Vision – Partial demodulation � Part 2 � Multiple Color – Variation in luminance and chromaticity Spatial Frequency Channels – Elimination � Luminance ‐ Color Interactions • Diffraction by the pupil � Part 3 � Introduction to • Radial chromatic aberration Phase and Position � Spatial – Slightly different wavelengths are differentially Localization in Visual System magnified � Part 4 – Producing beats for extended patterns � Physiology of Phase and Position Sensitivity 13 � Some Limitations in the Visual System Spatial CSFs � Part 1 � Color Spatial CSF � Significance of How different is the Color Spatial CSF from Luminance Spatial CSF? Color CSFs for 1. Sooner sensitivity fall ‐ off on high ‐ frequency for pure color Vision patterns. � Part 2 2. Color CSF is low ‐ pass while Luminance CSF is band ‐ pass. � Multiple Color Spatial Frequency Channels � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 14 � Some Limitations in the Visual System 7

RG vs. BY grating � Part 1 � Color Spatial CSF � Significance of Color CSFs for • R.L. DeValois & K.K. De Valois, 1975; Vision � Part 2 Boynton, 1979; Hurvich, 1981 � Multiple Color Spatial Frequency – Visual system color analysis: Channels � Luminance ‐ Color • Black ‐ white axis Interactions � Part 3 • Red ‐ Green axis (RG) � Introduction to • Yellow ‐ Blue axis (YB) Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 15 � Some Limitations in the Visual System RG vs. YB grating � Part 1 � Color Spatial CSF � Significance of • Little information on RG & YB Color CSFs for Vision � Part 2 • Both have the similar sensitivity � Multiple Color Spatial Frequency • YB gratings fall off sooner in high Channels � Luminance ‐ Color frequencies Interactions � Part 3 • Might be because of sparse distribution of S � Introduction to Phase and Position cones. � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 16 � Some Limitations in the Visual System 8

RG vs. YB grating � Part 1 � Color Spatial CSF � Significance of Color CSFs for Mullen (1985) : no difference Vision � Part 2 – Effects of chromatic aberration � Multiple Color Spatial Frequency • Affect blue ‐ yellow more than red ‐ green Channels grating � Luminance ‐ Color Interactions � Part 3 � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 17 � Some Limitations in the Visual System Temporal CSFs � Part 1 � Color Spatial CSF � Significance of Color CSFs for Vision • Experiments by Regan & Tyler ,1971; D.H. Kelly, 1974,1975 � Part 2 conclude: � Multiple Color Spatial Frequency – Temporal color CSF differs from Temporal luminance CSF in: Channels • No low temporal � Luminance ‐ Color Interactions frequency attenuation � Part 3 • Having lower high temporal frequency cut � Introduction to Phase and Position � Spatial Localization in Visual System � Part 4 � Physiology of Phase and Position Sensitivity 18 � Some Limitations in the Visual System 9