Measuring the visible range of high-dynamic-range images

We made pairs of identical film transparencies. We viewed one (single-contrast), then two super- imposed in registration (double-contrast). Single-contrast images have 2.7 logIH dynamic range; double-contrast ones 5.4 logIH range. Observers estimated the appearance of 40 gray areas sur- rounded with white and black blocks of different sizes. First, the surround had equal white and black areas (average single-contrast luminance 􏰝 50.01% max; double-contrast 􏰝 50.00% max). Doubling the contrast had minimal effect on retinal glare. Magnitude estimates show nearly the same plot (appearance vs log luminance) for both contrasts in the range of 0.0 to 2.3, and no discrimination at higher optical densities. Second, with a 8% white ^ 92% black surround appear- ances ranged from 0.0 to 2.7. Increasing the stimulus range had little effect on appearance. Decreasing the white area of the surround decreased veiling glare and increased the range of usable densities. These, and other experiments, measure how veiling glare controls the range of appearance in high-dynamic-range images.