Chapter 6 Color Constancy and Contextual Effects on Color Appearance Maria Olkkonen and Vebjørn Ekroll Abstract Color is a useful cue to object properties such as object identity and state (e.g., edibility), and color information supports important communicative functions. Although the perceived color of objects is related to their physical surface properties, this relationship is not straightforward. The ambiguity in perceived color arises because the light entering the eyes contains information about both surface reflectance and prevailing illumination. The challenge of color constancy is to estimate surface reflectance from this mixed signal. In addition to illumination, the spatial context of an object may also affect its color appearance. In this chapter, we discuss how viewing context affects color percepts. We highlight some important results from previous research, and move on to discuss what could help us make further progress in the field. Some promising avenues for future research include using individual differences to help in theory development, and integrating more naturalistic scenes and tasks along with model comparison into color constancy and color appearance research. Keywords Color perception • Color constancy • Color appearance • Context • Psychophysics • Individual differences 6.1 Introduction Color is a useful cue to object properties such as object identity and state (e.g., edibility), and color information supports important communicative functions [1]. Although the perceived color of objects is related to their physical surface properties, M. Olkkonen, M.A. (Psych), Dr. rer. nat. (*) Department of Psychology, Science Laboratories, Durham University, South Road, Durham DH1 3LE, UK Institute of Behavioural Sciences, University of Helsinki, Siltavuorenpenger 1A, 00014 Helsinki, Finland e-mail:
[email protected]; maria.olkkonen@helsinki.fi V.