I’ve been using Darktable (DT) for quite a while now. I don’t consider myself a real knowledgeable photography and there are lots of camera capabilities that I simply do not understand. However, I do like to take pictures of natural scenes and wildlife which is normally done in normal daylight. I do realize that there is something called white balance that pertains to digital color representation. I think 6500 Kelvin or thereabouts is what applies to my normal daylight. The DT “white balance” module typically shows a similar number when I’m editing my pictures. However, the automatically included “color calibration” module shows values that are extremely different. For example below 4000 Kelvin. Furthermore DT seems to insist that you can only use one or the other of those modules. In that, trying to use both is said to conflict and prevented.
It also happens that, for my images, I can usually improve the displayed image significantly by turning off the “color calibration” module. While that is easy to do and, in my case, is always something that needs to be tried I certainly can not explain why the module is automatically included in the pipeline.
Don’t worry about those numbers. Darktable’s internal pipeline uses D50, not D65, so it maps temperatures relative to those white points. 6500 K is mapped to 5000 K, 6000 K to something like 4600, and so on. The CCT values you see in color calibration are the mapped (adapted) values, while you see the original ones in white balance.
No, that’s wrong, you need both, and darktable does not say such a thing. However, you need to set white balance either to camera reference or as shot to reference.
Some cameras have wrong values in the colour matrix, and that does break color calibration. The workaround is described in the manual.
That implies to me that you are not supposed to do it. Rather only use color calibration module for adjusting white balance.
It would be true that the numbers do not matter much to me but I often do like to adjust the color and that is often where something a bit artificial makes the picture look better from my perspective. As best I can tell the white balance module does something I want to do whereas there is nothing else in the color calibration that I want to do and depending on the image file it does not even portray white balance but rather something else, that I don’t remember at the moment, which is meaningless to me. Then how am I supposed to change white balance. My answer is deactivate the color calibration module.
In conclusion, I think color calibration is quite complex and I certainly don’t understand everything it might allow me to do but as yet I haven’t seen any reason to.
If I am not mistaken, you can set a legacy wb workflow (I.e., just using white balance and not color calibration rgb) independently from the scene- vs. display-referred workflow in the settings.
The comment from @kofa is correct. And I agree it’s “Some cameras…” I do not recommend trying to go back to an older workflow.
The manual discusses this topic, but it’s quite technical.
Recommended practice is to leave the white balance module alone and make any adjustments in color calibration. Personally, I start with illuminant to “as shot in camera,” and judge whether any further changes are needed. I might then change to another illuminant (usually either Daylight or Custom), but only when necessary.
Color calibration is a complex module that includes a color channel mixer. Boris has a nice video or two on the topic, if you are interested. I would suggest a 2nd instance of color calibration for any channel mixing.
Edit: corrected wording to indicate white balance.
Using CC sometimes might not give you a pleasing “WB” infact its not a WB but a perceptual CAT on the pixel data instead of simple r,g,b coefficients applied equally to all the data. So items that are neutral or white or indeed hopefully, most of the colors will look similar when viewed under the editing conditions as they would have in the scene…
If you start to think in terms of the scene illuminant rather than temperature it becomes a little easier to understand…
THe manual does a pretty good job of explaining the implementation.
Aurelien has done an nice overview that is perhaps better and added it to his Ansel documentation…
Another good reference, keeping in mind there is some math, but you can read between the lines to understand how and why the CAT is applied.
Well, you can still use only the “white balance” module, and disable color calibration (that’s what we did for years before “color calibration” came along).
But if you use “color calibration”, you have to use “white balance” as well: some modules between those two (in pixel pipe order) need to get input that’s at least approximately white balanced (e.g. “demosaic”)*. And to make sure “color calibration” has a reliable starting point, you should set “white balance” to either ‘camera reference’ or ‘as shot to reference’. The full reasoning is explained in the thread introducing “color calibration”
I suppose you mean to leave “white balance” alone (but enabled)? Color balance is not a module for white balancing at all, but its use is recommended when using filmic to increase chroma/saturation to taste. Sigmoid and AgX seem to rely less on color balance for color grading (I rarely use those tone mappers).
I have a pull request that will allow exact white balancing via white balance, and leave only the adaptation to color calibration, but it’s not high prio.
