David Pettersson wrote a post on gain maps that has a nice HDR example which he describes :
"LinkedIn re-encodes everything you post and discards the metadata gain maps live in. What survives is the ICC profile, which means: PQ-encode the pixels, embed a Rec.2020 PQ profile and let the color management do its work."
The result is an image with luminance turned up to 11.
But I was curious how embedding a Rec. 2020 PQ 1200 nit profile would compare to a gain mapped version.
So starting with these tone control knobs by Vogler I created the scaled and cropped version below.
To compare with David's result, I used PIL to extract the ICC profile from his example image :
The resulting profile is here. PIL can also be used to embed this profile in an image :
Simply embedding this profile with the above cropped image though is gnarly. The source image also has to be PQ encoded. Since we're starting with a SDR image the color chapuza will be to desaturate and reduce the contrast as hown below :
And now when the Rec. 2020 PQ 1200 nit profile is embedded the HDR version is :
The appearance of the overhead lighting reflected off the top of the knobs really pops.
In comparison, I also genearted a version of the tone control knobs with a gain map. In this case the original scaled and cropped version was used as input. The resulting gain mapped version is below :
Similar but different.
In this case I decided to keep more of the warmth in the original image. In addition, with gain maps its easier to create local luminance adjustments.
Note that the above HDR images require your hardware/OS/browser to all support HDR rendering.
If you are viewing this with SDR only rendering, the results will not be evident.
