I’ve found the Film Negative tool in both RT and ART appimages:
RawTherapee_dev_5.8-2463-g1ed9444_20200911
ART_master_1.5.2_20200914
The tool doesn’t show the same options you show above. Is this an experimental version of RT?
Ok, i think you’re using the dev branch; the latest version is in the filmneg branch. I don’t think there are pre-built binaries available.
See this previous post for info on how to build the branch from sources 
Thanks, I’ll check it out later. Yes, I was using the dev branch.
True. I tend to see things too much from the point of view of the programmer 
The filmneg branch is now updated with the inverted blue slider. I’ve also moved the blue slider above the green, to mimic the WB tool.
By extension of your reasoning, i could even make the slider compensate the color temperature, instead of just scaling the blue channel. That way, the “warmer” side of the slider would tend to orange instead of yellow, as happens with the regular WB tool.
Maybe that could make the interaction even more familiar ?
Yeah, for sure let’s try that! I felt something a bit peculiar about the current slider and now you explained it with the yellow vs orange, so it would be interesting to compare the feelings. Maybe you can provide it as an option to quickly try both approaches in the same session…
Pushed to filmneg branch 
I’ve tried, but that’s a bit complicated… anyway, you can quickly try both versions by making a copy of the old executable before compiling the new version.
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I’ve tried the latest commit, it feels super!!! Thank you, I think you should settle on this variant.
Appreciate your speed of response!!
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Hi @rom9, if I may suggest one small UI improvement: maybe this “Pick white balance spot” button shouldn’t deactivate itself after single use? If I’m not happy with the result, I might want to pick some other spot, but now I need to click button again. It would be easier if it works just like standard WB tool picker, which is active until some other tool is selected.
or until you right click in the preview
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Hi @rom9! I think I’ve found a bug in the latest commit. How to reproduce:
- Make one photo good looking.
- Press ctrl-c to copy processing profile
- Paste it to another frame from the same roll, apply curves so it looks correct too.
- Then double click this second frame to zoom 1:1. The picture suddenly turns green as if you’ve touched the green balance slider! I’ve reproduced it several times, so it’s not rare.
Absolutely right! Done
Didn’t know about that 
! Done
Yes you’re right, i’ve noticed it yesterday but still didn’t push the fix, i forgot to call setEditedState on the green slider. Now it should work correctly.
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I’ve taken the latest commit 2d8dd5c6b… and built it but the bug is still there…
I’ve touched the first photo to ensure it saves the sliders. Then copied the profile from the first photo to the second one. Then touched curves. The colors look correct on the second photo. Now double click it and it’s green again.
Ok, i think i’ve found the bug. Can you try again with the last commit?
Thanks for your patience
Thank you very much! It works great now!
In the latest commit, i’ve fixed some other bugs related to batch mode.
Moreover, i’ve re-labeled the color balance sliders to make it clear that the blue slider performs a color temperature compensation.
I didn’t want to name it “Temperature”, since it would be a lie (this value has no correlation with the actual color temperature of the original scene), so i used some vague labels “Cool/Warm” and “Magenta/Green” :
Also, the value displayed in the blue slider is not an absolute temperature value, but is a ratio to a reference “neutral” temperature; when it’s set to 1.0, the picked spot is balanced to neutral gray.
I wanted to find the most intuitive and less confusing way to present the settings, but i’m not sure about this solution…
Any opinion is much appreciated, because i really suck at GUIs 
You can give me a high five
One observation… In my experience, this default option (FilmNeg profile) gives much poorer results than the Working one, no matter what points I sample. So I just never use it. Wonder if it’s just with my camera (Nikon d750) or with others too.
So maybe having the Working as the default one could be a better choice.
So, please at least don’t delete the Working one, it’s the only option that gives great results for me 
Ilya, can you perhaps post an example that benefits from doing stuff in the working space?
Sure. Just any photo I tried looks better in Working. In fact, the FilmNeg profile looks just like the intermediate version after rom9’s initial summer refactoring which I disliked. And the working one looks like the early spring version, before the refactoring. So I guess that profile was the true reason of that summer’s behavior, not refactoring per se. The Working one looks true to life, the filmneg one has this hard to describe dirty green-magenta-look with colors like yellow and green really close together and impossible to separate using color controls.
So, the latest version, “Working” profile, the good one:
The “FilmNegative (built-in)” profile:
(the same raw file is used as I posted here in the summer)
Of course, each was resampled after switching the profile (using the same black/white spots on the bus cockpit and then “pick white balance spot” on the bus)
Yes, i noticed this with your sample picture. Interestingly, if you set the color temperature in the main WB tool to 3150 - 3200K instead of the current 5531K, you’ll see that the result with filmneg colorspace is much better.
I have no idea why this happens; in theory it should work correctly with the backlight color temperature, and in fact it does with my Sony ARW files.
This must be somehow related to the input profile, but i don’t know how.
Anyway, to get the same result as the previous version, you should choose “Camera” colorspace: that should give practically identical results as before.
In fact, i’m thinking maybe i should set “Camera” as default, in order to make the tool less surprising to old users … 
The “Camera” setting is also less critical to setup, since there is no colorspace conversion between tha main WB and the exponentiation, so a different value in the main WB cannot screw up the image as in the example above (the main WB and the filmneg tool color balance can in fact be used interchangably, they only apply channel coefficients before or after exponentiation).
Maybe we could treat Camera as the “basic / new user / default” setting, and Working-FilmNeg as the “advanced” settings ?
Opinions appreciated