Color curves & histograms in RawTherapee

Processing
1

I notice a funny thing - in RawTherapee, when I change, say, the green curve in the RGB curves, the green histogram changes. So far no surprise. What I don’t understand, and hopefully someone can explain to me, is why to the red and blue histograms also change when I’m only changing the green color curve?

Not as easy to see in Gimp, but it didn’t seem like Gimp behaves the same way, ie. if you change the green color curve in Gimp, only the green histogram changes.

(I tried it on a JPEG too, with no fancy raw processing or demosaicing applied, and changing one color curve still causes the other two histograms to change also)

2

Perhaps the working color space (does it default to ProPhoto RGB?) is different from the output color space which the histogram is generated from.

If you adjust the brightness of a single channel, the conversation matrix will cause there to be an effect on the other channels too.

3

Correct @CarVac.
@mbietenholz if you change the working profile from the default of ProPhoto to sRGB, the histogram will behave as you expect. But using a different working profile just so that the histogram behaves in some way is not a good reason for doing so.