Effect of the Absorption Pigment Hue on Sparkle and Graininess Perception

ABSTRACT

Special effect pigments are widely used to enhance the visual appearance of industrial coatings, producing texture‐related attributes such as sparkle and graininess. Previous studies have shown that sparkle visibility is related to the contrast between bright pigment features and their surrounding background and have reported relationships between physical or image‐based descriptors and visual assessments across different coating hues. However, the extent to which absorption pigment hue influences the perception of sparkle and graininess remains to be systematically clarified. In this work, the effect of background hue on the visual perception of sparkle and graininess is investigated using controlled psychophysical experiments. Two sets of automotive coating samples were utilized. The first combined three metallic pigment particle sizes with three absorption pigment hues (red, green, and blue), while the second maintained a constant texture structure and varied the absorption pigment hue over a wide range of hue angles. Visual assessments were carried out using a forced‐choice triplet comparison method under directional illumination for sparkle and diffuse illumination for graininess. Observer responses were analyzed using multidimensional scaling, and intra‐ and inter‐observer variability were evaluated. The results show a strong linear relationship between perceived texture and metallic pigment particle size. In contrast, no statistically significant dependence of either sparkle or graininess perception on absorption pigment hue was observed under the tested conditions. Moreover, the multidimensional scaling results indicate that a single perceptual dimension is sufficient to describe the variation in texture assessments for the samples investigated. These findings suggest that, for the limited and specific set of samples and viewing conditions studied, background hue does not play a relevant role in the perception of these texture attributes. The results provide further evidence supporting the use of hue‐independent, potentially achromatic, perceptual scales for sparkle and graininess, while further studies with larger and more diverse sample sets are needed to assess the generality of these findings.