Veiling glare : the dynamic range limit of HDR images

High Dynamic Range (HDR) images are superior to conventional images. However, veiling glare is a physical limit to HDR image acquisition and display. We performed camera calibration experiments using a single test target with 40 luminance patches covering a luminance range of 18,619:1. Veiling glare is a scene-dependent physical limit of the camera and the lens. Multiple exposures cannot accurately reconstruct scene luminances beyond the veiling glare limit. Human observer experiments, using the same targets, showed that image-dependent intraocular scatter changes identical display luminances into different retinal luminances. Vision's contrast mechanism further distorts any correlation of scene luminance and appearance. There must be reasons, other than accurate luminance, that explains the improvement in HDR images. The multiple exposure technique significantly improves digital quantization. The improved quantization allows displays to present better spatial information to humans. When human vision looks at high-dynamic range displays, it processes them using spatial comparisons.