Hi,
1. Vibrance is supposed to be *{ RGB } = Y + saturation * ( { RGB } - Y
)^vibrance*, where Y is the luminance channel from XYZ space, and { RGB
} a pixel vector. This way, you perform both operations at once. Also,
using (R + G + B) / 3 instead of Y is generally not a good idea since it
has no perceptual background (R = G = B values does not equal visual
grey in every RGB space, RGB is just a random vector space until a
proper profile is applied).
2. The basic adjustments module is a double edged sword : yes, it's nice
to have a unified *UI* to quickely set-up pictures, but it's not just an
UI, it's also an image operation that gathers at once several operations
that need to be done at different places of the pixel pipe to get proper
results :
* exposure is a scene-referred operations that needs to be done
preferable before input coulour profile, since input matrices are
optimized approximations for mid-tones and skin-tones, in order to
put the RGB values in this sweet spot before applying the profile
* saturation needs to happen after the input matrice, when the Y
channel is defined (actually, input matrices only profile the
conversion from camera RGB to XYZ),
* contrast needs to happen after any frequency filter.
TL;DR the model/view/controller architecture got violated here.
Cheers,
Aurélien.
Le 10/10/2019 à 21:21, Keresztes Barna a écrit :
> On Thu, Oct 10, 2019 at 8:58 PM parafin <para...@paraf.in
> <mailto:para...@paraf.in>> wrote:
>
> Is it any different from velvia iop in darktable?
>
>
> Yes, it affects colors less than Velvia. It doesn't intend to emulate
> film.
> The results of this slider are very similar to the standalone Vibrance
> tool.
> There are some important differences:
> - The formula I use is different. It is run earlier in the pipeline,
> in the RGB color space (Vibrance tool runs on Lab)
> - This slider allows negative vibrance settings (so you can fade the
> colors without totally desaturating them)
> - it's a part of the Basic Adjustments tool, it can be used easily to
> set the color "amplitude" in the image together with the saturation
> slider.
> - It has a larger amplitude, so the results are more visible
> (sometimes the original Vibrance tool is barely perceptible).
>
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