i know 
In scene referred, perhaps it is better to use blending mode RGB (scene) and lightness, instead of HSV lightness
for me, “HSV lightness” is the better alternative. For me, all other blend modes have too strong effects on other colors, which shouldn’t mean that it can’t be appropriate.
Interesting, they may not be talking about the same thing but on the Krita site where they were discussing painting and the scene referred workflow they say HSV is okay…I wonder if they are referring to the same thing just using the same acronym??
KRITA DOCS
""Okay, but why isn’t this all the rage then?
Simply put, because while it’s easier in the long run, you will also have to drop tools and change habits…
In particular, there are many tools in a digital painter’s toolbox that have hard-coded assumptions about black and white.
A very simple but massive problem is one with inversion. Inverting colors is done code-wise by taking the color for white and subtracting the color you want to invert from it. It’s used in many blending modes. But often the color white is hardcoded in these filters. There’s currently no application out there that allows you to define the value range that inversion is done with, so inverting is useless. And that also means the filters and blending modes that use it, such as (but not limited to)…
Screen (invert+multiply+invert)
Overlay (screens values below midtone-value, in sRGB this would be middle gray)
Color-dodge (divides the lower color with an inversion of the top one)
Color-burn (inverts the lower color and then divides it by the top color)
Hardlight (a different way of doing overlay, including the inversion)
Softlight (uses several inversions along the way)
Conversely Multiply, Linear Dodge/Addition (they’re the same thing), Subtract, Divide, Darker (only compares colors’ channel values), Lighter (ditto), and Difference are fine to use, as long as the program you use doesn’t do weird clipping there.
Another one is HSL, HSI and HSY algorithms. They too need to assume something about the top value to allow scaling to white. HSV doesn’t have this problem. So it’s best to use an HSV color selector.
For the blending modes that use HSY, there’s always the issue that they tend to be hardcoded to sRGB/Rec. 709 values, but are otherwise fine (and they give actually far more correct results in a linear space). So these are not a good idea to use with wide-gamut colorspaces, and due to the assumption about black and white, not with scene linear painting. The following blending modes use them:
Color
Luminosity
Saturation
Darker Color (uses luminosity to determine the color)
Lighter Color (Ditto)
So that is the blending modes. Many filters suffer from similar issues, and in many applications, filters aren’t adjusted to work with arbitrary whites."""
A simple solution is to go to the Color Zones module in Darktable. Use the eyedropper to select the blue color of the sky and then raise this portion of the curve in the lightness tab.
Yes but there is a lot of blue in the statue, so you lose some details - and masking around the statue is a bit fiddly to define
I retested my idea of using Color Zones. Before doing any adjustment I took a snap shot and then I adjusted the brightness of blue using the lightness tab. There was no detectable change in the statue. The woman’s blue jeans did alter, but none of the earthy tones of the statute so I see no need for masking. Out of interest I created a parametric mask based upon the blue colour of the sky and this quickly masked out the statute, but the only small change this made was around the leaves of the palm tree in the sky and was not significant. I look forward to CR3 files working in DT very soon because I am not sure what would be loss during the DNG conversion.
Nice photo. Thought I would try my hand at it.
darktable-3.5.0+1170~gb428b0d7f-win64.exe
ER6_4832_10.dng.xmp (24.0 KB)
The blue of the sky around the palm trees on the right was very problematic.
Just scene referred with 1.0 EV bump and three patches altered in the color lookup module…it actually worked fairly well…Did one small mask around her jeans but you could easily mask the sky to control this even better…I have taken using the module a lot lately…even some time selecting the white patch and just dropping the lightness or one of the first couple of grey patches can …I stress can really add a nice touch to highlights without much effort…
ER6_4832.dng.xmp (8.7 KB)
Sky darkened easily …
Add a strait tone curve blended 10% subtract and it gets even deeper…
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Todd,
The Color LUT is an interesting option, because although it works in LAB space and is deprecated, it does have a predictable impact on the image. Pick a section of sky, and increase/decrease lightness and/or saturation with easy-to-use sliders.
Is it possible to get the same effects in the color balance module with a parametric mask that picks out all pixels with a given hue?
My subjects are very different from yours and I also use a very different camera … however, like yourself I do find that my raw images appear to have more blue than I would like to see. My solution is to use a color-zone preset that I can easily apply. For me taste this provides a little less saturation and a little more lightness … but that is simply a personal preference. It is also easy also to adjust the preset for more severe cases.
I would say yes…so take the picker and select the sky …by default it will select the opposing hue so just add 180 t the number if below 180 or subtract 180 if the number is above 180 and then you can add saturation and adjust lightness…it might be targeted enough just trying the highlights or mids this way or you could mask…
I’m just looking now…I though originally you wanted to drop the blue but you wanted to lighten it…stupid me…just reverse my explanation but you can still use the Color Lut module for a nice easy upgrade to the sky…I don’t think its depreciated its just part of the display referred workflow and honestly again if you get the results you need just use it…you really don’t have to be so rigid with the modules…
I tried your suggestion of using the Color Balance Hue colour picker to pick a patch of sky then add 180 to get the opposing hue. I did this in the mid-tones, but this has an additional effect of pushing up the saturation and factor. Is this what you expect? Although it is easy to correct the sliders back to a reasonable image.
Also I have noticed that both techniques tend to push a lot of patches out of gamut. The picture still looks OK though.
Color-zone is far easier to apply with control of saturation and lightness.
It is, but I have the same question about pushing colours out-of-gamut.
I think Color Zones behaves less well regarding gamut, and I would be interested in the experts views on whether this matters if the sky still looks natural enough.
“Looks good” trumps everything technical in my book.
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What is your setting for histogram profile and gamut limits…these can be deceptive and often the output profile has to map them to fit a Jpg file anyway…https://discuss.pixls.us/t/color-spaces-nightmares-gamut-clipping-wtf/22085...As for CB it should not change the level (level has its own picker) only the hue and saturation . I only use them for color casts or to enhance so I rarely change the hue it picks…I just use the 180 degrees if trying to enhance and as is if correcting a cast and then I adjust as needed with the saturation…I do the same with color calibration. I always switch to custom to display the hue chroma sliders and I adjust the chroma to suit my taste…
I use the CB as it is used here https://www.youtube.com/watch?v=OXjWJmV_F6c
How are you assessing out of gamut??
These options will matter. I usually just use luminance and judge Saturation by eye.
Also I use AP’s recommendation to set my histogram profile to linear rec2020 ie my working profile…if I keep the histogram in good shape while editing then I have never violated the data and the output profile will remap …I use perceptual but there are instances where some might choose relative…If you set you histogram profile to sRGB you will show gamut and clipping all the time
This is how i have it set up …if I want to reference the sRGB histogram I turn on softproofing which I have set to that …other profiles are the profiles for each of my monitors…
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