Geometry of illumination, luminance contrast, and gloss perception

Abstract

The influence of both the geometry of illumination and luminance contrast on gloss perception has been examined using the method of paired comparison. Six achromatic glass samples having different lightness were illuminated by two light sources. Only one of these light sources was visible in reflection by the observer. By separate adjustment of the intensity of both light sources, the luminance of both the reflected image and the adjacent off-specular surroundings could be individually varied. It was found that visual gloss appraisal did not correlate with instrumentally measured specular gloss; however, psychometric contrast seemed to be a much better correlate. It has become clear that not only the sample surface characteristics determine gloss perception: the illumination geometry could be an even more important factor.

Estimating the Material Properties of Fabric from Video

“…Video Stimuli Stimuli included the videos of 30 common fabrics exposed to 3 different strengths of wind from our database (Section 3). A paired comparison method was used to measure perceived differences in the stiffness and density between the fabrics in two videos [8]. Specifically, a subject was shown two videos of fabric stimuli moving by either the same or a different wind force and then was asked to report which fabric was stiffer, the fabric in video A or B, by answering on a 7-point scale provided underneath the videos (Figure 3).…”

A unified account of gloss and lightness perception in terms of gamut relativity

“…According to theoretical approaches based on the classical computational view of vision [4][5][6], the visual system computes lightness and gloss at each image location as a function of spatial image gradients correlated to diffuse and specular reflectance components, respectively [7][8][9][10][11]. The modularity inherent in this notion has spawned a surfeit of perceptually and computationally formulated theories of gloss and lightness perception [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]-each with a limited explanatory rangerather than a unified, predictive theory.…”

Metrological issues related to BRDF measurements around the specular direction in the particular case of glossy surfaces

“…WR2n2G3 appears to be quite matte, although it has a specular gloss value (60° geometry) of 35 gu. Yet, it is well known that matte white samples are usually over-rated by a glossmeter [22]. WR3n2G4, on the other hand, looks highly glossy.…”