Glare-limited Appearances in HDR Images

Alessandro Rizzi John J. McCann Abstract — Intraocular glare and simultaneous contrast control appearance in high-dynamic-range (HDR) images. This paper describes unique test targets that simulate real images. These targets change the HDR range by 500 times, without significantly changing the veiling glare on the retina. As well, these targets have nearly constant simultaneous contrast. The range of appearances possible from HDR images with different average luminances were measured. The targets displayed a maximum luminance range of 5.4 log units. Using magnitude estimates (MagEst) of appearances, the relationship between luminance and lightness from white to black was measured. With one exception, only small changes in appearance with large changes in dynamic range were found. It was also found that appearance was scene-dependent. The same dark grays (MagEst = 10) were observed with luminances of 10, 4.2, 1.1, and 0.063, depending on the percentage of white area in the surround. Glare from more white increases the retinal luminance of the test areas. Simultaneous contrast counteracts glare by making the appearance range (white–black) with a much smaller range of luminances. Appearance is controlled by both the optical scattered light and the spatial processing. A single tone-scale function of luminance cannot describe appearance controlled by scatter and spatial processing.