If I wanted to convert a RAW file into a negative style image, is that something that I can do in darktable? Or is that something best done with GIMP?
I am wanting to play around with some “alternative” printing processes (salt, cyanotype, etc) but I only have access to digital cameras.
Thanks for any help/advice you can send my way!
Hi, how about negadoctor?
Invert a tone curve.
@manu : negadoctor is the opposite, isn’t it? Helping to convert a photographed negative into an image?
@AtaraxicShrug : have you seen Spectral film simulations from scratch ?
@kofa you’re right this is what negadoctor is for, but give it a try and see what is happening when you activate it on a positive image…
Don’t know if it’s a good solution, though. Just an idea.
@manu I didnt even think about negadoctor for the same reason @kofa mentioned. I had a look and I might be able to make that work, although I would be doing adjustments blindly. Negadoctor does not convert in an unbiased way given that it has a default state. I would need to play with the settings to get back to the positive. That may not be a bad exercise, since I assume there could be value in being able to identify how you want to adjust an image merely by looking at a negative.
@paperdigits In GIMP i believe this is the way you do things, but I am unsure how to accomplish that in dt. A quick try in tone eq and filmic did not do what I need.
Maybe you could ask Andrea (@arctic) if there’s a point where you can capture the negative his tool generates?
You should be able to do this with any software that has a control-point tone curve. Just drag the bottom-left point to the bottom-right, then drag the top-right point to the top-left. Ta-Da, negative.
Ok i feel dumb now.
I completely forgot about the host of modules that dt has but that do not show up when you limit things to scene-referred workflow.
I literally just use the tone curve module and place it at the end of the pipeline…
Thanks everyone!
So you don’t need the orange tint etc?
@AtaraxicShrug, If you are after simulations of a negatives based on real film stocks, you can get a decently realistic virtual scan of a negative with agx-emulsion.
Here is a quick example example (virtual negative and virtual RA-4 print):
compute negative tick box).
I am not sure this is the tool that could let you experiment easily with other virtual printing processes. I am interested in them if you get any good ideas/results, though. 
The GIMP can not open raw files directly but can be set to open in for example RawTherapee which can and which transfers the converted image to the GIMP on exit. Or convert the raw elsewhere.
The GIMP has three ways to invert an image: invert; linear invert; value invert. Here they are … your call …
@kofa For the initial set of processes I am looking at playing with, I do not. Although I understand that certain processes can be quite sensitive to small changes, so it is something I will probably experiment with later on.
@arctic I have not had an opportunity to check out your film sim stuff. It looks great though! I am mostly going to be working B&W to start (I have to keep it simple until I get the hang of things), so some of the hard work you did would be lost on me. That grain and halation section is calling my name however… 
@cedric Thanks for pointing that out! As I get more familiar with things I will have to have a play.
This evening I was put in touch with someone who has a fair bit of experience with alternative processing and they told me to go look at this site: https://www.alternativephotography.com/ if I want to get my feet wet. It has soooo much info!
Funny enough they actually have a step by step process of creating negatives from digital images in GIMP. At least for cyanotypes. I was hoping to avoid having to go learn more software right now, but I need to start learning GIMP anyway. Guess this is as good a time as any lol
