How to "swap" colors in darktable?


(Hardy Wang) #1

When I see many stunning processing result (for example https://petapixel.com/2016/04/04/one-popular-photographer-edits-photos/ with before and after comparison) I always noticed the original picture’s colors are “swapped”, e.g sky color from very light blue to orange??

What module should I use in darktable to achieve similar result? And what techniques are involved?


(darix) #2

Just guessing… tone mapping maybe?


#3

Give a try:


(Mica) #4

I would say, for the orange sky, a gradient mask or tone curve with parametric mask, or color zones with parametric mask.


(Hardy Wang) #5

Wow, great! I have checked the first tutorial, it looks like the main works is around channel mixer. Now I have 2 questions here

  • How to understand how channel mixer works? It seems that the author just fiddled colors in red channel. But I don’t quite get what R/G/B mean inside a color channel? Doesn’t a color channel only has 1 single color?
  • How does blend mode impacts the color?

(Morgan Hardwood) #6

Swapping to me means replacing red with green, for instance, and from what I see, no colors were swapped. What I do see plenty of is changing the hue according to the luminance, e.g. making dark tones in the clouds more blue and light areas where the sun breaks through more fiery (see the photo of Manarola), and then overlaying a graduated hue mask on top of that (clearly visible in both the photos of Xingping village and the cormoran fisherman).


(Hardy Wang) #7

Care to explain a little further how to “change the hue according to the luminance” in darktable?


(Morgan Hardwood) #8

I do care, but I’m not the right person to answer that.


#9

https://www.darktable.org/usermanual/en/color_group.html#color_zones would be a first start.


#10

Hi hardywang,

the channel mixer in darktable can be used to build up one destination-channel out of the color-information of the R, G or B channel of the picture.

A bit confusing is the fact, that the destination channel can not only be R, G or B, but also saturation, hue, lightness or greyscale.

Not an easy to use tool in my opinion, because it is sometimes difficult to estimate the information in the source-channels.

An easy way to understand what´s going on is, if you set destination to greyscale and then R, G or B separately to 1.0, take a snapshot of each and compare them.

Greets
Jürgen


(Mica) #11

A post was split to a new topic: Pictures changing color on export