HDR in Consideration of the Abilities of the Human Visual System

In recent years, high dynamic range (HDR) has been improved enormously. The capability of cameras and displays to reproduce small differences in luminance levels is constantly growing. However, we are still dealing with a limitation of the human visual system (HVS) known as the simultaneous contrast range (SCR). Compared to earlier studies, this paper focuses on real-world scenarios for evaluating the SCR. In natural images, bright highlights, especially in HDR, can limit the eyes' sensitivity to small differences in surrounding dark areas. This paper describes a test-image set developed as part of current research activities by the authors to measure the relation between the perceived SCR and the following four significant parameters: the distance, or rather, the viewing angle; the size of the bright highlight; the luminance of the highlight; and the ambient light. As a result, a mathematical formula is given that can help to evaluate and improve HDR viewing experiences as well as standard dynamic range downconversions.