A field study of visual perception of complex natural targets through atmospheric haze by naïve observers

An air quality–visibility perception study was carried out in southern California in July and August of 2002. The study was designed to make simultaneous state-of-the-art measurements of human perception, physical light intensities from natural targets, and particle scattering coefficient of the atmosphere. The purpose of the study was to obtain data needed to estimate the probability of seeing a change in haze due to a decrease in extinction coefficient of the atmosphere. The basic results of the visibility perception study are given. The focus is on quantitative measurements of human perception of lightness, hue and chroma (or colorfulness) of natural and artificial targets determined by an advanced color matching instrument and training protocol that made it possible to use naïve observers. The lightness, chroma, and hue calculated from the CIE X, Y, and Z measured by a 16-bit industrial imaging photometer are compared to those actually reported by the observers under varying levels of haze. The results are consistent with the results of two previous visibility perception studies carried out in national parks in the USA.