I quickly want to share the results of some experiments of doing the auto adjustment in GIMP. I didn’t fully automate all steps from the raw file to a jpeg (yet), but for the GIMP part I just slightly had to modify an example I found to add the inverting part.
The files are placed in
~/.gimp-2.x/scripts/ or in case of using flatpak (as 2.10 has support for 16 bit tiffs) in
~/.var/app/org.gimp.GIMP/config/GIMP/2.10/scripts/. Then, the following command processes the tiffs in-place:
gimp -i -b '(batch-invert-levels-stretch "*.tif")' -b '(gimp-quit 0)'
Using that, the workflow is
- in darktable, crop and disable the base curve
- export as 16bit tiff
- batch-process the tiffs using the GIMP command above
Here is an overview of the results in comparison with the flatbed scanner results (and also a zip with the full size jpgs). I also tested not disabling the base curve and doing the color inversion using darktable (tone curve with auto RGB mode), but the results are always worse. Also a few other test pictures (that I don’t want to share here because they show people) confirm that. Note that I didn’t do any other processing (e.g. contrast) on purpose.processed_pictures_gimp_batch.zip (54.3 MB)
I think the automatic results are good enough for me as a first step. Manual processing is always an option to do later (or in a few decades…) for the pictures that are important enough.
Thanks again to everybody who has posted here! And of course, if someone still has thoughts on how to better process the negatives or can explain why the invert module in darktable is not working as expected, I’m always interested.