In the color picker section, if you check the “restrict histogram to selection”, it doesn’t work in the vectorscope mode.
Maybe is not easy to do because it would be only one point in there. But in any case, here is my question/request
Thats not specific for vectorscope. See restrict histogram to selection is lost on edits · Issue #8680 · darktable-org/darktable · GitHub
have a look at vectorscope: add log scaling by dtorop · Pull Request #8885 · darktable-org/darktable · GitHub for the new log mode.
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I think that it’s a smart implementation. Thanks for the effort!
Tested vectorscope today. Looks like a really useful tool to understand colorscience.
Being a complete noob on this I have the following question:
I’ve set up an image containing 8 colour squares. Playing with saturation its nice to see how the endpoints of the colour vectors are varying. I thought that the continuous coloured lines in the vectorscope showing on the left and right side of the display are the gamut boundaries of the chosen input colour profile.
So why does gamut indicator of the blue colour square (#3 from above) indicates “out of gamut” here while the vectors are all well inside the boundaries ?
Settings:
- input colour profile: Linear REC2020
- softproof profile: Linear REC2020
- histogram profile: softproof profile
img_8944.cr2 (32.5 MB)
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IMG_8944.CR2.xmp (11.4 KB)
What gamut setting are you using?
Soft proofing is set to “Linear REC2020”. Or do you mean something else ?
No you have a choice for the indicator full gamut luminance one channel etc in the options under the right click menu
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In a recent English video Aurelien Pierre explains all of this in detail minus the vectorscope The video where he rants a bit (I say rant as I think ghat was in the title) and demonstrates color calibration on a photo of a blonde model…gamut settings and issues are fully explained
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I think you mean the settings of the clipping indicator:
For my test I did not use the clipping indicator, but the gamut checking (the right highlighted one). When it toggles, it shows a cyan color, the thresholds of the clipping indicator don’t apply for it.
Right clicking on the gamut toggle you can’t set a threshold, only the setting for the color profiles.
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I don’t know if the vectorscope remaps its colorspace when you activate the gamut checking so gamut checking is against the softproofing profile but I don’t know if the vectorscope changes from jhz or whatever the new colorspace is so that may be why it still looks fine in the vectorscope even though you show as out of gamut. I.m sure someone here will chime in with a correct explanation. I could see the vectorscope display change but it didn’t look to be showing out of gamut??
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Finally I’ve published the video.
I hope this will help (a little bit) 
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Nice video @Lander_corleone, thanks for posting.
Together with @priort’s tips and links and some additional reading I finally found out where I screwed up: gamut checking with a vectorscope would need a special functionality, e.g. some sort of overlay, which I think is not integrated here. Like you demonstrated in your video, a vectorscope is mainly used to judge the hue and chroma of the colours and to support colour balancing.
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The gamut triangle shows the 3 primaries in UV, CbCr or similar space, but doesn’t show you the Luminance (Y). You’re effectively looking down on the available colour volume.
So for example if you’re using BT.709, RGB [0 0 1] when converted to YCbCr = [0.0722 0.150 0.060]. If you try the Maths, you can find that at that point on the Vectorscope, if you have a Y value above or below 0.0722, when you convert back to RGB you’ll end up with values above 1 and below 0 in RGB, i.e. be out of gamut. (Same effect in other colour spaces, but you get different numbers)
For non-achromatic points on the Vectorscope, you can get values of Y that put you out of Gamut. Visualising the actual available colour volume is hard: https://lab.irt.de/hdr-crystal-colour-space-visualization-in-3d/
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Thanks for this additional information 
.
I continue working with it and I’ve realized that if you select something with the color-picker, that color appears in the vectorscope! Really really helpful!
Yep they just need to fix the restrict to histogram setting so it holds and doesnt cancel as soon as you make an adjustment
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