Processing tips - Red channel

rawprocessing
darktable

#1

Hello,
I am trying to get rid of this red peak on the right without affecting the rest of the picture.
Channel mixer in darktable just moves it left or right. Any ideas?


(Mica) #2

You could try the HSV module. You need to restrict it to the red channel somehow.


#3

I did not actually find HSV module in darktable (which is weird) so I tried to reduce the saturation with a mask by color but wasn’t able to do that.
At the end I used “color zones” module and pulled the red area down slightly. The histogram did not change much but I liked the result (faces on the picture were not that red anymore).


(Mica) #4

Its not called HSV… I can’t think of what its called off the top of my head, sorry.


#5

I personally like using the color balance module more than the color zone module, because I found it easier to fine tune adjustments using sliders, rather than dragging a curve as in the color zone module.


(Alex Mozheiko) #6

@Andrius it’s hard to figure out what module to use unless one can see the image in question. also it looks from the histyogram that WB is not adjusted properly
judging by the histogram - the peak is in the highlights, maybe this is a sunset - where a red peak is always on the brighter side, hence there is also blue shift.
anyway, there must be a patch with bright red.
virtually I’d try a channel mixer in the red channel, however would limit it strictly to lighter parts with drawn and/or parametric mask - this will allow smoothing the peak without touching the left side of the histogram.
then, if still an issue, I’d kill it with shifting the hue band in a color zone module, provided there is a mask to focus on the problematic area.


#7

I was never able to make the color balance module work for me. As soon as I touch red the picture gets too greenish


#8

I was not able to find a way how to apply a mask by color and bright areas but I guess I will keep playing . There are so many good things in DT so you never stop learning.


#9

I wonder: could the color look up table module be of use to you?


#10

The module only allows to change the output profile from sRGB to Adobe RGB, linear Rec709 RGB, linear Rec2020 RGB and BRG (for testing). I am not sure how it could help me to remove red pixels in the highlights / bright areas. Am I missing something?


#11

That’s output color profile. The color lookup table modules is a new one in 2.2


#12

"[quote=“Andrius, post:8, topic:3487, full:true”]
I was not able to find a way how to apply a mask by color and bright areas but I guess I will keep playing . There are so many good things in DT so you never stop learning.
[/quote]

You can use parametric mask at both “L channel” and “Hue” to mask by color and brightness. IMO, parametric mask is THE killer feature in darktable !!