-Assessing image quality is an important aspect of developing new display technology. A particularly challenging assessment is determining whether a bitwise lossy operation is visually lossless. We define "visually lossless" and describe a new standard for a subjective procedure to assess whether the image quality meets these criteria. Assessments are made between a reference image and temporally interleaved reference and test images using a forced-choice procedure. In extensive testing, we have validated that this method is suitable for discriminating between subtle differences in image rendering and is free of observer bias or criteria variability. The results of these tests demonstrate the efficacy of using as few as five randomly chosen observers. We have found that the subjective testing is more reliable than several widely available image quality metrics. As part of this work, we release a database of nearly 0.25 million subjective responses collected from 35 observers to 18 different images. The study uses a largely within-subjects design and tested observers from two viewing distances. We encourage the use of this dataset in future research to refine objective image quality metrics to improve predictability of subtle but potentially visible compression-induced image impairments.

VESA Display Stream Compression (DSC) is a light-weight codec designed for visually lossless compression over display links. Such high-performance algorithms must be evaluated subjectively to assess whether the codec meets visually lossless criteria. Here we present the first large-scale evaluation of DSC1.2 according to ISO/IEC 29170-2.

Increasing the purity of a visual stimulus increases its brightness, even if the stimulus luminance is held constant. This perceptual phenomenon is known as the Helmholtz-Kohlrausch (H-K) Effect. This paper reviews published experimental data and models of the effect. Using past experimental data, we derive a modification of the CIECAM02 and CAM16 color appearance models to account for the H-K effect and compare the proposed model to other models. Finally, we discuss the need for further experimental data on the H-K effect to refine the proposed model.

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Metrics that predict the perceptual brightness of displayed imagery are vitally important, especially as wide color gamut, high dynamic range displays become more widespread. We implemented a color appearance modeling pipeline derived from the iCAM image color appearance framework and CAM76 color appearance model that allows for the accurate prediction of color appearance attributes, such as brightness, colorfulness, and vividness, of high dynamic range displayed imagery. Building on previous work on the Perceptual Contrast Length metric, we propose an updated Color Perceptual Contrast Length that correlates well with subjective ratings of display brightness.