I would like to understand the difference between :
IMG > Desaturate
and
IMG > Desaturate > edit->fade (hue mode)
(of course same difference with a luminosity layer).

I've seen the difference and still can't explain it to me.
What is exactly Desaturate ? What is the link with saturation ?


Thanx,
Hugo.

When you desaturate it will simply remove color, averaging the values by dividing the sum by three. Now, if we use the original color over this newly made desaturated layer, it won't look like an original image.

Now, if you go to fade an set it to any of the following modes: color, hue, saturation, it'll give a result closer to the original based on human perception of color and light, meaning it's not just stripping the area of color, but adjusting lightness of pixels as well. Blues are much darker then reds for example.

So desaturation at normal mode= averages the values by brightness and ignores the impact color has on luminosity.
Desaturation in color, hue, saturation= that is what we want most of the time. Exact in terms of human perception, NOT in terms of averaging the values in three channels within each pixel. More like G*0.59+R*0.3+B*0.11.

EDIT:when you're an idiot and not looking while writing. Thanks AK Mac. Switched my titles and explanations.

Thanx for your quick answers !

I'm a moron, yes, yes!