A Visual Model for Very Wide-Gamut HDR Displays That Accounts for the Helmholtz–Kohlrausch Effect

Bibliographic Reference(s)

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• C. Demers, “Peak Brightness of TVs—Max Luminosity and HDR Highlights” for RTINGS.com, Jun. 2016. Accessed: Jul. 2, 2020. [Online]. Available: https://www.rtings.com/tv/tests/picture-quality/peak-brightnessto remove any possible bias. The “—” results indicate the images were not tested for the particular question. As found in Experiment 1, a red foreground object stands out well, catches viewers’ attention, and should be rated as a highlighted region-of-interest object for computational purposes. The data shows significant viewer preference for Display A when PCLCOLOR exceeded 20%. The viewers overwhelmingly chose the display with more saturated colors and narrower primary color bandwidth. In one case, image # 53, viewers split their decision. This particular picture contained the brightest white (around a light fixture), but significantly less saturated color than any other pictures in the set. In terms of choosing a brighter or more vivid picture, our hypothesis is confirmed in a qualitative fashion and should be followed by another experiment to assess viewer reaction in degrees of PCLCOLOR. We note another singular result for image # 69 where viewers predominately favored Display A. However, the PCL ratio is the highest score in this test set, yet not preferred unanimously as might be expected by such a high computational score. This image will also be a subject of further study in a future phase. Excluding this one outlier, the subjective scoring correlated well with the PCL ratio, as shown by a Pearson correlation equal to 0.93. Discussion The evidence, both computationally and subjectively, supports integrating Nayatani’s model for H–K effect amplification with iCAM06 HDR image analysis. Furthermore, we used a critical reference display, but while valid, such a display is not practical for multiple demonstrations. Some HDR displays and certain cinema projectors in the market are expanding the boundaries of color range beyond DCI-P3; therefore, our study of colors beyond DCI-P3 is relevant. This paper has described a metrology and display analysis procedure that quantifies the brightness amplification when displays render highly saturated colors that extend beyond DCI-P3. However, we stopped short of recommending how the content delivery ecosystem should adapt to the study. There is prolific evidence of material technologies, such as quantum dot, increasing the primary color saturation and expanding the colors viewable on a display. We call for an industry dialogue to consider how to implement a production flow that makes use of greater and brighter color. SMPTE published SMPTE 428-121 and SMPTE 431-1 in 2006; it is natural to expect that state-of-the-art displays today can produce more colors that consumers will find desirable. Subjective testing with binary scoring has been useful and stable. We suggest further quantifying the brightness, colorfulness, vividness, and realism by testing with a larger population and image set and questioning with a Lickert-based scoring system. Undoubtedly, the code base we developed will be further refined to become of even greater value to the EXTERNAL
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• ITU-R BT.2020-2 [Active]
• SMPTE ST 428-1:2006 [Superseded]
• SMPTE ST 431-1:2006 [Active, Reaffirmed]