HPA Tech Retreat: Perceptual Difference Between 4K and 8K

Warner Bros. vice president of technology Michael Zink described the results of a test, conducted with several partners, to resolve questions about the impact of higher resolution displays with larger screen sizes on the user experience. The test did so by assessing the perceptibility of 4K vs. 8K on a consumer 8K TV displays at a typical viewing distance for various types of content. Partners included the ASC, with content from Pixar and Amazon Prime, and LG for its 88-inch 8K OLED TV display.

Zink reported that participants watched seven clips of 10 seconds each that were shot in native 8K, with the 4K HDR content derived from the 8K material. Content included “Dunkirk,” “Tick,” “Brave,” “A Bug’s Life,” a nature show, 8K film scans, 8K animation and 8K RED Digital footage.

The uncompressed 8K playback system for the 10bit BT 2100 PQ7680x4320/24p Format DPX Files went from a PC with Intel 18-code i9 CPU & SSD RAID & Nvidia Geforce 1080Ti GPU through a Blackmagic 8K Pro video interface (Quad SDI) and 4x AJA SDI-to-HDMI and Autodesk HDMI 2.0 to HDMI 2.1 converters to the TV set.

A total of 139 people participated in groups of five. The viewing procedure, in which participants were seated five and nine feet from the screen, was a double blind, with each sequence consisting of two versions of the same clip, presented twice, in different order, to make it as random as possible. One factor that made a difference was the visual acuity of the viewers. Twenty-seven percent had better than 20/20 vision, 34 percent had 20/20 vision and 39 percent had less than 20/20 vision.

Across all participants, on average, 8K was, at best, rated “slightly better” than 4K, although the majority found 4K and 8K to be the same. “Confidence intervals overlap, therefore there’s no conclusion about difference between clips,” said Zink, who noted that only a single clip out of seven got a majority vote for a better 8K look. “With all the other clips, a vote for a better 8K look was in the minority.”

“It was an interesting experience,” he concluded. “Test results show that increasing resolution from 4K to 8K under typical viewing conditions did not result in significantly improved visual difference. We also learned that perceptual difference is highly content dependent, and tied to vision science. Viewers with 20/10 vision in the front row confidently rated two of the 8K clips slightly better. A lot more work needs to be done, but this was a great jumping off point.”

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