HDR (HLG) Test Footage Direct from a GH5s; ungraded

In this video I test the HDR recording capabilities of the Panasonic GH5s' HLG mode with different exposure settings. (150mbps, 30fps, 10-bit, HLG, MOV) My goal is to figure out what exposure is best to avoid added post processing, if at all possible. You will need an HDR display to correctly experience this video in full.

YouTube supports HDR video playback if you have an HDR-enabled display and a correct setup. If you do not have an HDR display, this video may only be of partial interest to you as it will playback in only SDR mode.

HDR video essentially provides more details in the highlights of video, which would either normally be compressed (flattened with a gamma roll off or clipped to be pure white). A monitor that supports HDR is needed to view HDR content correctly, as the monitor needs to be able to display very bright highlights with high contrast. In practice, over 800 nits peak brightness (HDR) versus ~150 nits peak (SDR). As well, 20,000:1 contrast vs 1000:1 contrast.

HLG (hybrid log gamma) is a unique form of HDR that was made in part by the BBC as a free HDR standard that is largely backwards compatible with regular SDR setups and software. The GH5S can produce HDR video either by recording directly with the HDR-ready HLG profile or converted into an HDR format after recording in v-LOG format and doing post-production. Cinelike-D mode could perhaps also be made into HDR video, in post-production, but to less effect.

While with Dobly-Vision and such you need to provide added metadata in a file to define brightness curves, etc. HLG does not "need" added meta-data. HLG is half a standard gamma curve, which can be played back as normal on an SDR display without added info, and half logarithmic, which captures the highlight details for added highlight detail for playback on HDR displays.

Players like YouTube, VLC, and MPC all take guesses at what the HLG video 'gamma curve' looks like, and so they don't play back all equally, unfortunately. YouTube does a "best guess" currently to this, but you can "optionally" add meta-data to help it guess correctly. It's unfortunate that HDR in general still is facing so many such challenges.

Another such challenge is that when recording HLG video on the GH5s, I've noticed that the HLG option underexposes at +0ev for SDR content, so I need to over expose just to get a balanced image. Roughly +2ev helps balance the SDR image, but clipping is a bit harsh then. HDR-playback on Youtube has +2ev being over exposed, but +2/3ev or +0 looks okay. It appears that colour grading will be required still to get a good result, which is unfortunate, but it can still do in a pinch. Another solution I will look into is figuring out how to provide "meta data", calibrated for the GH5S, to Youtube, which I hope will help avoid needing to grade the footage. I'll update if I figure this out.

An added benefit though of over exposing the video is that you will be able to retain added details in the shadows for later post processing. If you do not over-expose, the shadow details will not be as recoverable as that of s/v-LOG video recording. Over exposing of course can cause an issue for playback. You may ultimately be better off just recording in LOG/RAW mode, if your workflow supports.