How to effectively recover the blue channel?

[dfcsd]

I have several images that consist of heavily saturated blues. These parts of the image visibly clip and I can’t find a good way to recover them.

After pulling down saturation of the “blue” and “lavender” channels in “colour equalizer”, the colours unclip, but they become purple.

After pulling down the “blue hue” in the “rgb primaries” module, they also unclip, but it alters the colours elsewhere in the image.

So is there no solution other than a local adjustment via masking? This case is not very complex, but how to go about, for example, christmas lights string, that has lots of different colours, blue included, all close to one another. That’d be too much work adjusting them by hand.

[s7habo (Boris Hajdukovic)]

Watch this episode:

Darktable Episode 77: New workflow with enhanced sigmoid and new primaries module

[dfcsd]

That did help, cheers!

I’m already using the sigmoid workflow, so the summary for me would be: in sigmoid module’s “primaries” tab change blue attenuation and rotation to unclip the colour, then use the rgb primaries module to rotate the hues in the right direction to reproduce the real colour.

Here’s the difficult image that I couldn’t get right, before and after:

[Terry (Terry Pinfold)]

@s7habo this new primary adjustments in Sigmoid is brilliant for troublesome stage lighting. You are also a legend with all the effort you put into making these training videos.