PROBLEMS CONNECTED WITH THE CONCEPT OF GLOSS

A summary of the most recent ideas about gloss is presented with specific attention to the problems raised by the evaluation of perceived gloss with physical quantities. Research work published on the problem of multidimensionality of gloss, as well as methods using several parameters to characterize gloss, are first mentioned. Then physical phenomena related to gloss are discussed from the points of view of physical optics, geometrical optics, and photometry. Experimental results are related to the theory. It is shown that a mirror element reflects light in such a way that its radiant intensity in the specular direction is independent of its area, contrary to the radiant intensity scattered by an isotropic diffuser. The consequences of this fact for the current measurement of gloss are developed, mainly, the arbitrary choice of any gloss scale. A proposal is made to relate the measured gloss to the luminance factor in the specular direction. Problems raised by the terminology are also discussed: terms are needed for the general phenomenon of gloss, for the perceptual aspect of gloss, and for the most widely measured photometric quantity related to gloss. Proposals for future work are made. (C) 1993 John Wiley & Sons, Inc.