It’s not perfect, but I’m getting there. I’m trying to utilize the Film Negative feature in RawTherapee 5.9 to convert DSLR/Mirrorless film scans taken in RAW format. Once I get a little further along, I’ll do a tutorial.
7 Likes
hello Rick,
i just signed up to tell you: Please do so. This would be very very helpful as there is not much documentation i could find so far.
If you or anyone else could tell me, how black and white negative conversion should work I’d appreciate very much!
Thanks, Bernd
1 Like
Hi Bernd,
A simple approach for B/W negatives is to apply an “upside-down” tone curve in the exposure tool, or the L* curve in L * a * b * Adjustments.
Certain B/W negatives like Ilford XP (chromogenic B/W) tend to have a blue/purple tinge, this can be removed with the Black-and-White tool in the Color tab.
This is a very outdated approach and quite unnecessary for RawTherapee. Just enable the Film Negative module and use that. For some information: Film Negative - RawPedia
1 Like
Thanks. I’m getting into a video series on a different topic right now, but I might make a break from that to do a Film Negative tutorial.
Sometimes, when Film Negative doesn’t (or can’t) get it quite right, it helps to resort to manual methods. Or at least, a combination of the two.
Sure! 
Sorry for the late reply, and for being away for so long from the forum… unfortunately it’s a complete mess at work, and i have little spare time. 
Anyway, @Rick thanks for your interest in the Film Negative module, please share any problem you might encounter, i’ll take a look.
3 Likes
Not sure if there is still interest in this topic but I think i got a pretty good workflow with great results.
First of all you need a light source that is very consistent in brightness as I found that changes in exposure messes with the white balance quite a bit. So better let the LED light panel warm up for a few minutes before scanning to avoid brightness shifts due to temperature changes of the LED’s.
Also it is important to shoot the whole film with the exactly same camera settings. The best practice is being in manual mode and set the ISO to 100, the aperture to 4-8 to have enough room for focus inconsistencies and better image quality in the corners and set the exposure so you get somewhere between 1-2 stops over-exposure in the meter of the camera.
Also very important is to shoot a picture of just the background light (using same focus point and aperture as for the film but faster shutter speed to avoid over-exposure without the film in place) and use this image as a flat-field image in the RAW-tab. This corrects vignetting of the ‘scanning’ lens and gives a really good brightness consistency (and white balance) across the whole frame.
You could verify this by taking a picture of an unexposed image (usually at the beginning of the film) and after Film negative conversion use the tone curve tool to move the top right white point towards the left which will blow out the highlights but shows you inconsistencies in the dark area caused by lens vignetting or uneven background light.
Next what i found, at least for my canon camera, is to use a custom Input-Profile for your camera model under Color Management in the Color-Tab. This together with ProPhoto working profile gives the best results. You can find the camera dcp profiles for many camera models here:
https://www.dropbox.com/scl/fo/h2bq18mwj5bgk3vxu5ehr/h/Camera?dl=0
Next you have to set the White Balance tool to custom and some white balance like 5000K or 6500K. Maybe you set it to your background light without film so it is neutral. The important thing is not to have camera or auto-whitebalance.
Next step is to turn off noise reduction (if it is on). This can cause some color shift (for color noise reduction) in the image due to the grain of the film which is usually bigger and looks different than noise from the camera sensor.
Turn off all shadow-highlight, tone mapping and dynamic range compression (which uses loads of CPU power for film somehow)
You can save these settings as a pre-processing profile. That makes it faster for new films.
Then either take a picture with the unexposed strip between two images to be in the middle of the picture, a fully unexposed image at the beginning of the film or take a picture wide enough to have the surrounding unexposed film in the picture. It should look now something like this:
2 Likes
Now we reach the point to turn ON the Film Negative tool. When you do this it will automatically white-balance the picture (without 20% of border and it will for now ignore any crop you did). Now this white balance step is also not good, because it depends on the content of the picture.
The better way is to use the black unexposed strip in the middle together with the white balance picker from the Film negative tool. This way we get the correct white-point of the film itself which does not change for the whole roll of film. You also can see how the “Input RGB” values are different and the Output Level changed too.
Next we set the output level to a higher value but not too high as it can blow out the whites of the picture.
The last important step is to adjust the Red Ratio and Blue Ratio to balance the film and get neutral grey and consistent color in the highlights like the sky (especially clouds should be neutral grey). Keep in mind that you should do this in a picture preferably with outdoor natural daytime lighting. The Film Negative tool contains a color picker for this “Pick Neutral Spots”-Button. When you activate this button first click one time in a bright neutral spot of the picture (but not an over-exposed part) and then click another time in a dark neutral spot in the picture. This will then set Red and Blue ratio for you. From there you can further tweak it manually to get a good result. The waveform graph can be helpful for that.
If you don’t have good bright and dark neutral spots in your picture just copy the processing settings to another picture to do that. Something like a grey road, white clothes, deep shadows and so on are helpful.
At this point you can copy and paste the processing settings to all other pictures of your scanned film. You will get consistent colors and true neutral blacks (except they have a tint from the lighting of the scene). If your negatives are under- or overexposed you can recover quite a lot by adjusting the Output Level and Reference Exponent of the Film Negative tool to change contrast and brightness in the picture and also use the Cool/Warm slider of the Film Negative tool to compensate for white balance shifts in your image due to different lighting of the scene (like indoor tunsten, outdoor evening, overcast shots and so on and use the Magenta/Green slider to correct color shifts due to older fluorescent lighting of the scene. You also can use it as a creative tool to make the film look more “filmy” by messing with the colors…
Keep in mind to not change the exposure of your camera that takes a picture of the negative. You won’t be able to recover more highlights or shadows but instead you change the white balance and mess up the colors.
The reason is that your camera can fully capture the full dynamic range of a negative image in one shot (using RAW)
5 Likes
With this workflow (white balance on unexposed film and change Red ratio and Blue Ratio) I can try to process the negative image from @Rick . But because it is not from a RAW file and I don’t have the correct camera input profile it is still a bit off…
Hi @sonnar and thanks for this write-up.
in the Any interest in a “film negative” feature in RT ? thread, I don’t recall getting a simple explanation why this step is important and how it actually affects the inversion, down the processing pipeline.
If you can comment on that, I’d appreciate!
Thanks.
Yes. Make one of your own, ideally with a transmissive target, for your particular light source.
If you use the white-balance tool from Film Negative it uses the RGB values after the white-balance was done from the RT pipeline. If you use the camera auto white-balance or RT auto white-balance then when copying your processing settings to a batch of pictures from the same film you could get variations in white balance which might be disturbing.
oh, ok, there was a misunderstanding — I was essentially wondering why you’d use the White Balance module at all. Is there a reason for that?
I’m simply deactivating it.
Oh you are right. Somehow I didn’t realize you can actually deactivate it 
But there is one benefit. The RT white balance works much better in correcting strong shifts in the white balance of the scene. Lets say very warm tungsten light is the light source. You can correct this after picking your white balance spot within Film negative tool.
Also i had problems before with Kodak Vision 500T film because its a Tungsten Balanced film. If you shoot in normal daylight and follow the guide then it’s very hard to use the red/green slider to get anything that looks realistic.
But using the RT white balance after selecting my film base white point you basically can change the film to be daylight white balanced (or think of it to virtually change the background light source to be more “warm” or “cold” color)
After this use the red/green slider to set the colors. I was surprised how well that actually worked.
But i need a color target (which i don’t have) to make this myself as described in this article:
https://rawpedia.rawtherapee.com/How_to_create_DCP_color_profiles
Thats why i use the profiles from Canon for this that i got from that link. The default DCP profiles for Canon from RT cause weird color shifts when using ProPhoto color space. They work better with AdobeRGB when using Film Negative tool. Don’t ask me why.
Ok, 9 months later, I’m coming back to this. I am uploading the RAW file along with the PP3 file in case anyone wants to take a stab at it. This frame was scanned with a Fuji X-T20 and Vivitar 55mm f/2.8 macro. Scanning bed (backlight) was a Digitiliza+ and I manually set the camera WB to 6600k. In RT, I set WB to Camera, used the custom color profile from the X-T4 (Provia) and adjusted from there. I will upload that custom file as well. If you’re successful with making adjustments, let me know what you did. TIA.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
DSCF8612.jpg.out.pp3
(14.4 KB)
Fujifilm X-Pro3 Adobe Standard provia.dcp (145.9 KB)
DSCF8612.RAF (47.9 MB)
EDIT: I’m getting much better results simply using the Auto-Matched Color Profile in Color Management, instead of the custom profile.
1 Like
Hello, I get this using Film Negative, CIECAM 2002, Local Contrast, Graduated Filter and White Balance.
DSCF8612-2.jpg.out.pp3 (13.9 KB)
Btw, this one is made with ART, using Color Negative, Tone Equalizer and Contrast. I like this one better, perhaps because ART is my default app.
DSCF8612_art.jpg.out.arp (11.1 KB)
I looked at the .RAF file for curiosity. But I see no piece of film-strip colour in there? The digitalize+ blocked it all? How do you know the filmstrip colour / blackpoint then?
This is what my CLI tool autodetects without having a filmstrip to scan. (It searches for the brightest spot then).
What you see here has the exposure raised a bit (and then highlights lowered to keep the detail in the clouds). This is without any custom profile or anything. (Loaded the file up into Rawtherapee, switched to neutral, rec2020 linear output, cropped to just the picture to get something that resembles a scanned .tif file, and this is what I got… isn’t that wrong, right?).
No clue what the original scene or the filmstock should look like ofcourse.
1 Like