Emulating Capture One colors

Hi,
For my camera (sony A6400) I like a lot the default tone and color settings produced by Capture One (I have v12).
C1 has an ICC profile for my camera that I can set DT to use. Problem is, C1 is also using some sort of tone curve before the input color profile.
After many attempts, I eventually managed to get a nearly perfect correspondence (using the DPReview studio scene), activating the following modules, in order:

  • unbreak input profile with linear=0.0218, gamma=0.45
  • base curve (or RGB curve) with preserve colors = none, manually tuned to match the L values of the greyscale patches in the studio scene
  • input color profile with the ICC camera profile from C1

Problems is, the base curve must be put before the input color profile, while the DT default order is after.
As far as I can see, a custom style cannot alter the modules order, so there is no way for me to apply those settings by default when opening RAW files.

Do you see any workaround ?

Marco

Yes. Embrace the logic of darktable because it’s sane. Display-referred workflows suck, base curves have no place before input profiles, it’s all bogus signal processing messed up by geeks who thought they could reinvent photography on their IDE and discarded 120 years of legacy as well as physics classes.

Just give me your C1 output, I’m pretty sure I can reproduce it with filmic and colour balance.

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Aurélien, thanks a lot for your reply.
I do use filmic and I acknowledge that it produces better results than basecurve when dealing with HDR scenes. With C1, although its highlights recovery is truly amazing, the results have a less natural, more digital look.
However, with normal DR scenes, for example with regular portrait studio work, I still find the basecurve workflow easier / quicker, with no visible color issues.
What I would need is a decent filmic “base point” preset for studio scenes. To be honest I tried, but I didn’t manage to create a decent one. So I accept your help with joy.

Here you can find:

  • the DPReview studio scene RAW file
  • the corresponding C1 output, default settings, 16 bit TIF file
  • In case you want to try my basecurve preset, the .dtstyle and the C1 ICC color profile. But you have to move the basecurve before input color profile to make it work

Marco

You can use “Using darktable-chart ” in the darktable usermanual to build a style mimicing the c1 output using the colorchecker chart in the image.

DT-Profile.zip (422.9 KB)
Use the attached profile they are for A6300 but the sensor are the same so should give you good results select Sony like base curve. One is made with CC and one with SG chart of x-rite. I have similar made for capture one too.
Please give your opinion after use.

“Display-referred workflows suck, base curves have no place before input profiles,”

Agree absolutely. So why does the channel mixer go after the base & tone curves?

It doesn’t anymore in dt 3.0. One more thing we have fixed.

Yay! Thank you.

I like C1 profiles for their sky and foliage colours but somehow I find I need to lower the saturation for skin tones – esp. the shadows get too saturated for my taste, probably because of the various RGB curves applied around the input profile. But I no longer use the C1 profiles with dt and do as @anon41087856 suggested, or use my own DCamProf profiles.

Are you sure C1 just use a base curve ? From what I see, they darken blues, desaturate greens, resaturate skin tones and shift them slightly toward red. I suspect there is an artistic LUT going on there, it does too many things at once to be a simple tone curve.

This is the closest I can get from the C1 output, using the provided .icm and only transfer functions:
Sony Alpha 6400.dtstyle (1,8 Ko)

Note that, if you truly want to achieve the same look that the C1, you will need to deal separately with colours, like desaturate greens and shift them slightly to cyan, darken cyan, lighten magenta, shift yellow slightly toward green and desaturate orange/yellow and resaturate reds. So I suggest you build a LUT: PIXLS.US - Profiling a camera with darktable-chart

Actually, the Phase One ICM profile contains 3 non-linear TRC:

So it’s easier to disregard this profile, use the Adobe DNG matrix (linear) and unroll filmic + base curve: Sony Alpha 6400 Adobe matrix.dtstyle (1,7 Ko)

But C1 still has an advantage on skin tones, and I bet they use a LUT to enhance reds and oranges, because, if you look at the colour checker, the primary patches look less saturated on C1 output, the green looks muted, yet the skin tones are more vibrant.

I am not surprised. Emulation doesn’t have to be exact. One simply needs to understand what is going on and then decide what to do with that info.

To be clear, I matched the lightness and contrast reproduction of the C1 output (± the algorithmic changes), and roughly the saturation reproduction, it’s the specific colours rendition that doesn’t match.

darktable output (filmic + colour balance with Adobe DNG convert matrix):

capture one output:

The norm and luminance are still quite different. The geometry doesn’t match either, so lots of flipping required â”»â”â”»ïž”ăƒœ(`Д®) ┻━┻

When I examine the orientation, there is more discontinuity next to the bottles in the dt rendition.

The grey ramp matches, so luma is ok. As I said, C1 adds red everywhere and mute the greens. For the bottle, it seems to be noise, probably linked to differences in black points. As for the distorsion, lensfun doesn’t have that lens + camera in database, so I picked the closest I got.

How do I get the Adobe DNG matrix ?

This? https://helpx.adobe.com/photoshop/using/adobe-dng-converter.html.

The Adobe DNG matrix is what darktable calls the standard input matrix, it’s already in the software and used automatically when you open the file.

I did some progress. Thanks everybody for the precious advice.

@Rajkhand: your profiles are pretty good, however they generate negative RGB values with saturated colors in the test image, don’t know why.

@anon41087856: you are right, C1 do use a LUT plus curves, so their look is difficult to replicate with standard tools.

All in all I found only two possible ways to replicate accurately C1 colors:

  1. Use their profile, which require a base curve (or RBG curve) before input color profile, which is not the default DT module order
  2. Use the standard color matrix + LUT. I have created a Hald clut using GMIC and it works very well. This method has also the advantage that I can replace the basecurve with filmic for HDR images. However for accurate results, the 3DLut module must be put after the basecurve / filmic, which again isn’t the default module order

At this point I have two questions:

  1. LUT are commonly used for artistic / color grading purposes, which is something you do after the tone adjustment. I believe the 3DLut module should be placed after basecurve / filmic, not before.
  2. More in general, in DT 3.0 the user can reorder modules, and I think it should be possible to save a custom module order in a .dtstyle.

What do you guys think ?
Marco