Possible case of filmic's preserve chrominance not applied in exporting

I have encountered something odd. In the preview of the raw file, filmic RGB does a great job with the deep magenta of the rose. The preview shows a nice looking smooth color that preserves detail.

When I export it , however, the colors don’t match. In fact, they look like what happens if filmic RGB is turned off. At first, I thought it was because the exported files gamut was too small. So, I changed it to export in the linear rec2020 color space. It made no difference. I also tried changing perceptual to relative colorimetric, which also made no difference. The file format is 16-bit tiff.

Here is a comparison of the color picker’s RGB values for various spots on the rose in the raw vs the exported file. Prior to export, the raw file’s RGB values all appear to be comfortably in-gamut for the working space (linear rec2020). So, I am not sure why the colors shift.

Darktable is the latest (at time of writing) 4.0.1 release, running on Windows 10. I uploaded the raw file with this post if anyone wants to see if they can replicate it. Anyone know what’s going on here, and how it can be fixed?

_DSC8850.ARW (16.1 MB)

You don’t need to use external sites, you can upload the raw here.

What output profile do you use?

linear rec2020.

Thanks, I got rid of the external link and uploaded here.

input at standard working should be linear rec2020 display should be the one that came with your monitor or a calibrated one you created and output for screen viewing most cases should be sRGB… Then you need to be sure that you don’t set something in export that changes that

If you export with Rec2020, which is the same as the working space, filmic won’t perform any kind of gamut mapping (only tone mapping).
What input profile do you use when re-loading the exported TIFF?
Can you upload your XMPs (both for the raw and for the TIFF)?
Also, can you show your soft-proof settings (so we can see what your display + histogram profile is)?
Have you run darktable-cmstest?
When you take screenshots, is the image grabber colour management aware (does it convert the values captured from display-space to sRGB)? If not, do you perform such a conversion? (It can be done using the Gimp, for example: assign the display space to the file captured by the screenshot app, then convert it to sRGB.)

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So for sure I think its something with your color profiles.

Your raw loaded in DT

Exposure and filmic only

Win11 photo app

JPG and TIff export side by side in DT…

Now on the left as you exported in rec2020 and on the right the one you expected in sRGB

Unless you have a good reason to change it, the output profile should be sRGB.

Right, like I said in the original post the only reason the final product is in linear rec2020 is because I thought perhaps the magenta colors were out of gamut for sRGB. To confirm this I deleted the tif file from darktable & the hard drive, and re-exported in sRGB. The same color shifting occurs.

What is your display profile… are other images impacted?? @kofa provided the laundry list of items that would likely provide the answer… xmp, confirm and provide all 4 profiles in use and show the export dialogue settings…

If you export with Rec2020, which is the same as the working space, filmic won’t perform any kind of gamut mapping (only tone mapping).

It does the same with exporting as sRGB. Linear Rec2020 was the last I tried because I thought perhaps the magenta color produced by filmic was out of gamut for sRGB.

What input profile do you use when re-loading the exported TIFF?

The embedded profile for the tiff. I also set the input manually to make sure it wasn’t an error with the embedded profile.

Have you run darktable-cmstest?

cmstest isn’t available for windows builds of darktable.

When you take screenshots, is the image grabber colour management aware (does it convert the values captured from display-space to sRGB)? If not, do you perform such a conversion? (It can be done using the Gimp, for example: assign the display space to the file captured by the screenshot app, then convert it to sRGB.)

That’s a good question, I’ll have to look into that. Nevertheless, if you look at the sampled RGB values from the color picker for the raw file w/filmic module on vs the exported tiff, you can see that they are measurably different.

xmp is attached. I attached the exported tiff as well.

_DSC8850.ARW.xmp (4.9 KB)
_DSC8850.tif (92.4 MB)

Export dialogue settings.

Input profile for raw - the standard default one for my camera in darktable
Export profile for raw - sRGB (in original post I had also tried linear rec2020, but tried sRGB again)
Input profile for tiff - embedded profile (sRGB)
Display profile - a calibrated profile created with argyll

On another note, I hooked up my secondary monitor and restarted darktable, and the difference between the raw preview and the exported tiff disappeared. The laptop’s built in screen does have a smaller gamut, so I guess it has something to do with that and/or the calibrated profile for the laptop.

My external screen has a wide color gamut (covers most of AdobeRGB and DisplayP3) so I guess the external screen and it’s associated calibrated profile are just better able to handle displaying deep magenta colors. I suppose this solves the problem in a practical sense, but it’s still curious that the preview of the raw does not match the output when displayed on the laptop’s native screen. Even when I click soft-proof (which is set to sRGB) the colors don’t match the export.

I guess I’ll just have to avoid editing while lying in bed with my laptop using the native screen if I want to ensure what I see is what I get on export. I suppose that’s what I get for being lazy :sweat_smile:

Since you are on windows, how are you applying this profile? To windows or to just darktable?

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Aurelien said in one of his last things in R&Darktable that there is no ‘color out’ step. I was kinda confused by what he meant, but he was unhappy with how color profiles are handled on export.
Since then, he made some changes to R&Darktable, which broke the export for me, so I never used it again :pensive: .

I also had some differences between what Darktable was showing me and what was in my final export. I switched for a while to exporting to linear-RGB instead of my using linear-rec2020 because of that.

These days, I have the output profile in the module list set to always match the output profile I’m actually using in the export section. Because I think they are somehow related.

So in the module list, the last module is output color profile. I set that to linear rec2020. I then (in the export section) export to linear-rec2020 (that is my own weird choice, not saying you have to do this as well!) and then use programs after Darktable has exported to resize and convert to normal sRGB for showing on the web (or going to printer, or going …).

As long as these two are aligned, I seem to have no differences in what filmic is giving me in the preview and what ends up being in my file.

edit: a quick edit exported from DT:

vs the screengrab:

I’m having the same problem!! Grrr, does that mean that rec2020 export is broken again?! :frowning: .

Confirmed :(. Setting output-color-profile module to sRGB and export to linear-rec709 and the image is correct.

So somewhere in the export it ‘assumes’ rgb or something, and when exporting to something else this skews the results from what you see on screen. I believed this was fixed at one point?!

I don’t see all these issues but I always just export to sRGB… Also this is not a filmic issue. I suspect anyone having these sort of issues has some sort of issue with their display profile as it has a key role in all this…

Can you clarify…

“Export one image in linear-rec2020, and one in linear rec709, and one in normal sRGB.
Open them in your favourite - colour managed - image viewer, and compare the differences. Now compare those images with what Darktable is showing on your screen while editing the image.”

Are you saying you are comparing the 3 exports you mention to how they look in the viewer and in DT or how they look compared to the image as displayed in DT from where you exported them…

2 being linear and one non linear sRGB… ???

So some time ago I went in and tried to be sure all my settings for OS and others were aligned… I don’t have a calibrated monitor. Maybe Santa will help on that front. So I am just sure that everywhere uses the icc that came from the manufacturer… I did as you described I think and did a quick little edit. Only some exposure and threw on sigmoid module. I then exported srgb, linear rec709 and 2020 and in both DT and FastStone and WIn 11 Photo’s all the images are rendered the same and look as they do in the edit… So I have something wrong (or not) or those calibrating their displays might have some nuance or maybe some other issues. I checked the tiff files and the exif data shows that the correct exported profiles are listed… So I am no help…

EDIT: Inserted rec2020 export into Word which I didn’t expect to be color managed… just to confirm…