Rec.2020 P3 Limited to YT: The Definitive Test?

For the past six months, we’ve been uploading Rec.2020 ST2084 (P3-D65 Limited) videos to YouTube, but it appears that many are still operating under the assumption that Rec.2020 videos constrained to P3 should not be uploaded to the video sharing platform. In order to settle this question once and for all, we recorded a billboard with super bright, highly saturated colors. The signage was so bright that, in order to prevent clipping of the highlights, it was necessary to stop the lens all the way down to f/13 at ISO 800.

In DaVinci Resolve Studio 18, we added a Gamut Limiter at the very end of the color pipeline to hard clip any colors beyond P3.

The screenshot shows two nodes. The one to the left is a LUT converting the timeline color space from RedWideGamutRGB/Log3G10 to Rec.2020 ST2084 1,000 nits. The one to the right is the Gamut Limiter, which will hard clip colors that fall outside the P3 gamut.

When switching the Gamut Limiter in DaVinci Resolve on/off, changes could be easily seen in the vectorscope, indicating the presence of colors that exceed P3, but the picture itself looked the same with the limiter on or off, because, like all displays, the XDR miniLED of the MacBook Pro cannot reproduce colors beyond P3. We also struggled to see any discernible difference at all between the original clip and the one uploaded to YouTube when viewing on either the MacBook Pro or on our LG CX.

We’d also like to offer these words of advice to those creating HDR videos for YouTube. Firstly, in project settings, on the color management page, it is important to set the correct value for “HDR mastering is for X”, which lets you specify the output, in nits, to be inserted as metadata into the HDMI stream being output, so that the display you’re connecting to correctly interprets it. In the case of the LG CX, that figure would be 700. Secondly, as the full screen brightness of OLED displays is < 20% of peak brightness, the average picture level (APL) of your grade should probably not exceed 200 nits. Lastly, we strongly recommend inserting MaxCLL and MaxFALL metada so that your videos look correct on displays with differing brightness and contrast capabilities.

By keeping APL at or below 200 nits and inserting MaxCLL and MaxFALL metadata, we were able to ensure that this video looks as good on our LG CX, with a peak brightness of 740 nits, as it does on our MacBook Pro (2021).

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