Exposing for Skin Tones, HLG HDR

Having watched Gerald Undone’s outstanding guide to exposing for low noise when shooting HLG for SDR delivery, I was curious whether the figures he arrived at were also applicable to HLG HDR video. Because even in graded HDR content, the bulk of the image should still fall within the standard 0-100 nit range, I wouldn’t expect metering for faces to be wildly different from SDR video except in situations where there are strong super-brights, in which case, in order to appear natural, the face would have to be exposed darker. Using both zebras and false color, Gerald calculated percentages for the skin tone patches on the X-Rite Colorchecker, and his findings were of particular interest to me because I primarily shoot people and have long been on the lookout for a more reliable method for getting consistently good exposures.

For my own test, using the X-Rite Colorchecker, I first metered the middle skin patch, placing it at 66% as Gerald recommends, and adjusted my camera accordingly. I then metered the white strip with zebras set to 95% and found I had to further reduce exposure by 1/3 stop to preserve detail in the highlights. The clip might have benefited from an additional 1/3 stop reduction in exposure. I have also come to realize that my skin tone falls closer to the first or second skin tone patch on the X-Rite Colorchecker, not the third!

Screen Shot 2019-10-14 at 11.16.41 AM

I shared the clip in black and white, as I don’t own an HDR reference monitor and therefore could not correct skin tones. I sent the unedited project directly to Compressor, where I transcoded the file to HEVC 10-bit (YouTube does not recognize 8-bit as HDR) and uploaded the clip to YouTube. It takes my 2017 iMac 27″ an hour to convert a three-minute clip. The video must be watched on an HDR device.

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