06 - The Human Visual System and HDR Tone Mapping

Abstract

The dynamic range of illumination in a real-world scene is high—on the order of 10,000 to 1 from highlights to shadows, and higher if light sources are directly visible. A much larger range of illumination can also occur if the scene includes both an outdoor area illuminated by sunlight and an indoor area illuminated by interior light. This chapter proposes the view that the modeling of human visual adaptation is the key to realistic tone mapping of HDR images. It is shown that photoreceptor adaptation is the most important factor responsible for visual adaptation. The relation between various tone-mapping algorithms and the photoreceptor adaptation model is made evident. Background intensity is a key component in this model. Some of the commonly used methods for computing this background intensity in images were discussed. The usefulness of a human visual model was also seen in realistic simulation of visual effects associated with the wide range of real-life illuminations. This chapter explores the similarities between several current tone-reproduction operators.