I would like to know, how do you edit a very high ISO image, only with FOSS and without using AI.
The following image has ISO 16000 (and still underexposed), also a very greenish color cast, but the skin tone is not important.
Any idea, what to do to improve it?
ISO_16000.CR3 (62.6 MB)
This file is licensed Creative Commons, By-Attribution, Share-Alike.
darktable 5.4, primarily using raw denoise & denoise (profiled) for noise reduction, color calibration to use shoes as neutral reference, then color balance rgb to resolve some little color casts.
Yeah, it’s hard. I definitely struggled to balance noise and detail here. I think I have the white balance ok, and I masked the skin highlights to bring them back up a little and remove a bit more of the green casting (most of which is taken care of in color calibration - I did the same as @thumper using the shoes as a reference.) - still didn’t get it all though.
Thanks all, very good edits! 
@tankist02 ART did a very good job!
I want to take a closer look at all your edits and compare them. By the way, do you know a quick method of loading more *.xmp files as duplicates in Darktable? My only idea right now: create first the duplicates in DT then copy the contents for every separate *.xml. 
Mainly denoise (profiled) at work here. My canon’s really hate underexposure because of noise. I have an R7 and 16000 ISO shouldn’t
ISO_16000.CR3.xmp (14.2 KB)
The way I do this (not sure if it’s the quickest, but it works for me):
In Darkroom, Create an ‘original’ duplicate of the image:
In Lighttable, select the new version (you might need to click the group unfold button to show the duplicates next to the original)
On the right, under History Stack, select load sidecar file
Select the downloaded XMP file and this will be applied as a new sidecar to the RAW, without merging it with your existing edits, and means you still only have to keep one copy of the RAW on disk.
NB: You don’t have to copy the sidecar file into the RAW folder here, just load it straight from your downloads folder.
I use the comments field to keep track of which is which, too. (just to avoid the risk of accidentally thinking an edit was mine 
)
With this complicated light situation, it’s probably really the best way to get rid of any colour.
yes, BNW was also my first thought. Besides that, zooming out makes the noise more visible. 
@hatsnp I would prefer the first version.
Zooming in is still possible. A bit of grain suites especially on B/W very well.
( I think this is the limit of noise reduction. Maybe a bit less would be better)
ISO_16000_01.CR3.xmp (57,9 KB)
ISO_16000.CR3.xmp (10.6 KB)
I just download the different xmp-files and rename them like this:
ISO_16000_01.CR3.xmp
ISO_16000_02.CR3.xmp
ISO_16000_03.CR3.xmp
Then i reload the directory and all the different versions are duplicates…
