VESA’s new HDR specification is designed for PC monitors and laptop displays that rely primarily on LCD displays. The DisplayHDR specification includes 3 levels (400, 600, and 1000 nits) but none of them actually define proper HDR.
VESA says that it is the “first fully open standard specifying high dynamic range (HDR) quality, including luminance, color gamut, bit depth and rise time”. Version 1.0 of the specification focuses on LCD PC monitors. A later version will address OLED and other display technologies.
While HDR is quickly gaining momentum in the TV industry, the PC industry has struggled to implement the end-to-end format. The majority of PC monitors are also based on edge-lit LCD panels that cannot faithfully reproduce HDR, despite claims by monitor manufacturers.
- "Developing this specification is a natural expansion of our range of video standards," said Bill Lempesis, VESA executive director. "Moreover, we are the first standards body to develop a publicly available test tool for HDR qualification, utilizing a methodology for the above-mentioned tests that end users can apply without having to invest in costly lab hardware. Most of the tests require only a colorimeter, which many users already own. Ease of testing was a must-have requirement in order to make DisplayHDR a truly viable, consumer-friendly spec."
To address the problem VESA has developed methodology and test tools to evaluate HDR on PC monitors. It has defined 3 levels of performance:
Baseline - DisplayHDR 400
Mid-range - DisplayHDR 600
High-end - DisplayHDR 1000
Not actually HDR
Unfortunately, the first 2 levels are based on specifications that do not qualify as HDR. For example, to obtain certification for ‘DisplayHDR 400’ any given PC monitor must cover only 95% of the BT.709 color space, which has been used throughout the HD era. All other HDR specifications typically require a wider color space of at least DCI-P3.
Also, a monitor must achieve “at least 955:1” contrast ratio, which VESA claims is “a value significantly more than typical LCD panels”. That may be true for contrast-poor IPS LCD panels but it is nowhere near HDR territory.
The ‘DisplayHDR 1000’ level is closer to the mark but the fact that monitors with poor black levels of up to 0.10 nits qualify should be cause for concern.
- "We selected 400 nits as the DisplayHDR specification's entry point for three key reasons," said Roland Wooster, chairman of the VESA task group responsible for DisplayHDR, and representative from Intel. "First, 400 nits is 50 percent brighter than typical SDR laptop displays. Second, the bit depth requirement is true 8-bit, whereas the vast majority of SDR panels are only 6-bit with dithering to simulate 8-bit video. Finally, the DisplayHDR 400 spec requires HDR-10 support and global dimming at a minimum. With this tiered specification, ranging from baseline to high-end HDR performance levels, PC makers will finally have consistent, measurable HDR performance parameters. Also, when buying a new PC, consumers will be able to view an HDR rating number that is meaningful and will reflect actual performance."
During FlatpanelsHD’s testing, we have found that HDR can only be faithfully reproduced on LCD panels with true zone dimming (full array local dimming), or preferably OLED panels with pixel-level luminance control.
More than two dozen companies, including AMD, Nvidia, Asus, Dell, LG, Microsoft, and Samsung, contributed to the development of DisplayHDR, VESA said.
New products complying with the DisplayHDR specification will be demonstrated at CES in Las Vegas next month. More information is available on displayhdr.org.