How to get gain_map of other devices?

[hiepgaf]

Hi @fkeglevich,
I want to get gain_map for my device, how to do this?
Thanks,

[fkeglevich]

Hi @hiepgaf
what is your device?

Because depending of phone/tablet that you are using the gain maps cannot be extracted automatically and need to be created by hand (it's not so difficult but it's a bit boring to do).

[hiepgaf]

Hi @fkeglevich,

My device is HTC U11.
Thanks for reply.

[fkeglevich]

Sorry for the late reply. I learned how to extract gain maps using the Lightroom DNG Flatfield plugin and ExifTool by Phil Harvey according to an youtube tutorial. Unfortunately it appears the youtube video was deleted.
But the main idea is:
You take a low-iso out-of-focus picture of a uniform white surface (ideally it should be made from acrylic, but a sheet of paper is good enough), under the illuminant of your interest (daylight, fluorescent light, incandescent...). The picture must contain only the white surface. Then you open the picture in Lightroom and use the Flatfield plugin to create a corrected picture. And finally, you can use Exiftool to extract the gain map from corrected picture; it should be on OpcodeList3 DNG tag.
I hope to have helped you in some way :)