February 4, 2015Human FactorsVisual Displays Sensation Receptor Cells Sensory encoding Single cell recording technique Sensory adaptation Adaptation levels Visual Acuity extent to which an image triggers specific points on the retina Affected by lens and distance between lens and the retina Hue red, blue, etc. chroma Brightness black-white axis Saturation ratio of hue to black-white Additive color mixtures: theater lights beam on the same target. Blue+yellow=gray/white Substractive mixture: each color actas as a partial filter Cones are differentially receptive to stimuli from shorter, medium and longer wavelengths 450nm blue, 550nm green, 650nm red Opponent process theory two types of cones, each with two pigments Yellow pigment doesnt really exist Color Blindness Defined by Ishihara plates Most profound, cant distinguish red/green Less dramatic color isperceptions 8% of males, 0.3% females Industrial color matching challenges Habituation to a small color band Matching 2+ colors at once Time pressure to decide Photopic and Scotopic Functions Photopic: Subjective brightness of a color light, differs by hue. Scotopic: Similar to photopic but under dark-adapted conditions Perception perspectives Gibson survival depends on perceiving the environment in as much detail as exits Feature detectors Invariant processes, optical illusions Gestalt whole is greater than the sum of its parts: brain organizes the image Hochberg perception is a combination of what is perceived and what is already known. Gestalt Laws of Form Figure-ground distinction Similarity Proximity Closure Symmetry we tend to interpret forms as mirror images around their central axes. Depth perception Binocular depth cues require 2eyes to detect Retinal disparity is the same image appearing on each retina? Different images? Object is closer Same image? Object is farther away Monocular depth cues can detect with 1 eye Linear perspective Relative height Interposition Motion Perception Apparent motion Criteria for Visual Displays Pick the right tool for the right job Speed of interpretation or reading Accuracy of interpretation or reading Speed of learning Comfort Absence of fatigue with long term use Small differences in human performance that can be traced to differences in the populations using the device The stability of performance under poor environmental conditions or stress Visibility Image clarity Location in field of vision Proximity to operator affect desired size of the display. Viewing distance also affects distinguishability. Interpretability Completeness Parallax effect High contrast Depth perception Color should not be the primary source of information about the display components