darktable curve modules: base... , tone... , RGB... ?

Perhaps this is a stupid question. What’s the difference, or when/what is the preferred curve module to use in darktable: base… , tone… , RGB… ? or where/how can I find this ?

It depends on your workflow. If you‘re using the ‚new‘ scene referred workflow, then you can ditch basecurve (tries to mimic camera jpeg processing) and there’s also no demand using tonecurves.
Take some time to read PIXLS.US - Darktable 3:RGB or Lab? Which Modules? Help!
& for a quickt start: darktable 3.0 for dummies (in 3 modules)

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@MStraeten probably better to link to the final pixls.us version of that article now (which has had some final polish since the hackmd version): PIXLS.US - Darktable 3:RGB or Lab? Which Modules? Help!


For a dt beginner like me these are complex matters. I try to interprete the bottomline when it comes to my initial question “when/what is the preferred curve module to use in darktable: base… , tone… , RGB… ?”. So I better avoid using those curve modules in favour of filmic. I am using filmic for a few weeks now and see that it has 4 tone curve options based on the options (hard/soft) for shadow contrast and highlights contrast. So I assume that the rest of tone editing should be handled by the tone equaliser, local contrast and contrast equaliser ? is that right ?

From a technical perspective, yes. But I still use the tone curve in LAB mode quite often, as I like what it does and I know how to control it. The placement of the modules in their default order will ensure you work the technically correct way. You can still use tone and rgb curve, but better to use the other modules first.

Not a dt user, but I think this perspective is appropriate:

From the camera, your image data has a linear relationship, based on the light captured. All of the ‘tone’ modules, base, tone, filmic, push and pull the data off that linear relationship for various ends, and there’s another tone curve you don’t usually deal with in the transform to your display or to a file. My inclination is to have as few of these operators in your processing chain as possible, as the tendency to cancel each other in portions of their curves is prevalent. I’ll try janking around filmic curve first, but if the particular image needs lifting or lowering that the filmic curve doesn’t accommodate, I’ll take it out and replace it with, usually, a control point curve. For my black-and-white images, I just go straight to the control-point curve, as one can do things to monochrome that persnickety color images won’t tolerate… :smiley:

The essential thing is to understand what the operator is doing to each part of the histogram, and then you can make informed tool selections. @aurelienpierre is doing some new work to the filmic curve depictor that look very promising in showing you what the tool is doing; use that information to make good choices…

Thank you Glenn, Mica. I must correct myself about the limitations of the tone curve within filmic because there are more options than only hard/soft for shadow contrast and highlights contrast. There is also hardness and contrast itself. But yes I heard you both: I may want to use the (probably RGB) curve to further tune the tones to my likings.

Actually, if you want to tune the tone mappings beyond what Filmic RGB does, better to use tone equaliser for that.

Matt, apparently your advice is then avoiding to use any of those curves beyond filmic, but rather do the rest of tone editing by the tone equaliser, local contrast and contrast equaliser ?
(as per my earlier understanding here above)

i’m using tonecurve indeed, but just to give an image the final touch (e.g. using t3mujinpack - film emulation presets for Darktable)

So first the image is proper exposed, the tonal range and colors are fine using the modules up to filmic in the pixelpipe:

  • using exposure to bring out proper midtones,
  • colorbalance to tune colors, saturation, and sometimes a bit of color contrast in combination with masks
  • contrast equalizer for contrast tuning and sharpening,
  • filmic to bring dynamic range in place
  • sometimes rgb curves or tone equalizer if some tonal ranges needs local improvements

Then after this basic stuff it’s time to work on the look (film presets with tonecurve, LUTs, split toning etc.pp.) …

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Thanks Martin for this workflow advice. I am starting to get familiar with all modules you mention here, except for color balance and rgb curves. The latter you seem to suggest as an alternative choice to tone equaliser. Instead of color balance I have started to use color zones. I will study the color balance module to understand what it brings.

Tone equalizer and rgb curves have a quite different approach. Tone equalizer operates using masks respecting edges (see tone-equalizer Masking - #26 by aurelienpierre) while rgb curves operates on the whole image.

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