Hue-Saturation without effect

[Krikor]

Hi,
I have an image formed by a gradient between red and white.
Basically the red saturation is 100% on the left and decreases as it goes to the right.

My question is about the Colors - Hue-Saturation... filter

If I make a selection on this image and apply a saturation adjustment via Colors - Saturation..., the change is visible, whether I increase or decrease the saturation.


However, if the adjustment is done via Colors - Hue Saturation... the change is only visible if I reduce the saturation. If the saturation is increased, even to 100%, nothing is noticeable.


Is it a bug or is this filter behaving as it should?

Thx!

[PixLab]

(11-02-2021, 11:44 PM)Krikor Wrote: Is it a bug or is this filter behaving as it should?

Thx!

That's normal! (yeah, that's not a bug )

The colors ➤ saturation modify saturation using LCH-based operations (LCH = Lightness Chroma Hue) with only 1 slider, thus you do need to move the lightness in the colors ➤ Hue-saturationto be able to do something "similar" ➤ it's quite different, though.
Roughly, those 2 filters are not the same even though there is the word saturation in it

A good ➤ Ref about it: https://ninedegreesbelow.com/photography...hroma.html (very interesting article with examples) given by this page https://docs.gimp.org/2.10/en/gimp-filte...ation.html
if you want to know more about hue-saturation as well ➤ https://docs.gimp.org/2.10/en/gimp-tool-...ation.html

[Krikor]

On the one hand, I'm glad it's not a problem with my version of Gimp. On the other hand, disappointed with this tool that doesn't seem to serve as intuitively expected of it.

Even at https://docs.gimp.org/ the definition of this adjustment is:

Quote:"Saturation: The slider and the input box allow you to select a saturation: -100, 100."

What as I showed in Figure 02 in post #1 is not what happens; or even is, as it allows you to select from 100, but without any effect.

PixLab, your answer was enlightening and your reading recommendations appreciated (I'll try to read the article at https://ninedegreesbelow.com/ as soon as I have some time).

Thank you!