This dissertation addresses the manner in which the human visual system perceives objects seen through atmospheric haze. Although this project was carried out with the perspective of an air quality scientist interested in the visual effects of air pollutants, it addresses the general phenomenon of perception of objects viewed through haze or fog. The information presented within is useful to scientists interested in digital imaging, artificial vision, military, transportation and psychology. A psychophysical approach is employed to relate the spectra of objects incident on the eye with the perception of this spectra by the visual system. This was done by measuring the spectra of objects with a high-resolution telespectrophotometer and also matching the color of objects as perceived by an on-site observer with a special outdoor colorimeter. Color appearance as measured by the spectrophotometer and as quantified by the colorimeter is calculated by a color appearance model. The color appearance model then outputs the hue, colorfulness and brightness for the spectra and for the colorimeter, which are then compared. Although spectral color appearance and perceived color appearance of nearby objects agreed well, those for objects viewed through haze did not. The spectral color appearance of objects viewed through haze was bluer and brighter than perceived color appearance. This is because most of the radiance in the spectra is due to path radiance. Path radiance is predominantly blue due to scattering by fine particles in the atmosphere. Although most of the radiance incident on our eye is blue, we still perceive the true color of the objects. This is because we discount the hue and brightness of the path radiance by perceptual semi-transparency. The psychological index that is sensitive to change in haze is the colorfulness of objects, which decreases exponentially with respect to a haze index such as the extinction coefficient.
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