Mechanisms of gloss perception

• Applicant: Dr. Franz Faul
• Subject Area: General, Cognitive and Mathematical Psychology
• Term: from 2016 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 285808412

The perception of gloss is an important aspect of material perception. It also has an important functional relevance, e.g. in the recognition of transparent objects and the detection of smooth or moist surfaces. The planned research project is primarily concerned with the regularities in the retinal image, which are used by the perception system to detect glossy objects and to quantify their material properties. The clarification of these questions is difficult, because gloss is closely related to the reflection of light sources or objects in the environment from the objects surface. For this reason, the retinal image is not only dependent on the material properties of the surface, but also to a considerable extent on the properties of the environment. In the project we will deal with two subtopics, which directly follow from preliminary work and results of the ongoing project. The main topic of the first subproject is how local glossiness cues, which are present at different surface points, e.g. isolated highlights, can be integrated into an overall gloss impression. To this end, we will, on the one hand, investigate materials which are inhomogeneous with regard to the physical gloss properties, and on the other hand, we will use complex illuminations, which consist of light sources with principally distinguishable properties. This makes it possible to systematically vary local stimulus properties and to measure the corresponding effect on the global gloss impression. A second subproject relates to an important result of the current project phase, namely that the visual system exploits the fact that the strength of the specular reflection depends on the direction of incidence of the light (Fresnel effect) when determining the glossiness of a surface. In many previous studies on gloss perception, such Fresnel effects have been neglected. It is therefore well possible that results obtained in such studies are of limited validity. In order to investigate this question and to quantify potential effects on gloss and gloss constancy, we will replicate some key studies on these topics with and without Fresnel effects. Theoretical considerations and informal observations further suggest that Fresnel effects also contain information that may be used in shape perception, and specific information about the color of the light sources that could be used in material recognition. Potential influences of Fresnel effects on shape and material perception will therefore also be investigated.

• DFG Programme: Research Grants