The Perceived Intra-Frame Dynamic Range in a Cinema Environment

When considering a higher contrast and luminance range in cinema, it's important to understand the limits of the Human Visual System (HVS) under cinema specific conditions. A user experiment with 36 participants was conducted in a cinema theatre. We assessed how the perceivable dynamic range evolved with different background gray levels and with the presence of local highlights in the image; how the size, position and intensity of these highlights affected the results. We found that the perceptual visibility of details in black depends greatly upon the image composition and the average luminance of a given image or image sequence. We found that in a fully dark frame the average person can detect black details down to 0.005 cd/m ² . However if a 0.25 cd/m ² gray background in the central field of view is presented this rises to 0.009cd/m ² and with a 2.5 cd/m ² gray background the black level threshold further increases to 0.015cd/m ² . In addition to the limitations of the HVS one needs to consider the limitations of a theatrical projection setup where bright elements in the image via reflections on the walls, ceiling, floor, seats and audience contaminate the black elements of the image. Even with special precautions in our test design to reduce those effects with a factor 20, with the presence of very bright highlights they were still found to be significant.