Editing moments with darktable

LOL. And in America, why do we drive on a parkway and park on a driveway?

3 Likes

I admit I am having trouble seeing how the tabs in the new color balance module work together. From your, @aurelienpierre, explanation, I am thinking you have changed the former slider name from saturation to chroma because that is really what it has always done?

I don’t grasp the global saturation sliders. Why not a (real) saturation slider to go below each hue slider? Or am I missing the point of luminance and chroma sliders?

I don’t get what you don’t get. What is a real saturation slider ? Or do you refer to the 4-ways saturation ? This one is the intensity of the color shift you define for each way : pick the hue of the deviation, and push it more or less along that hue with saturation, at constant luminance. While the global saturation is just making the pixel more or less colorfull at constant hue.

Yes, basically any “saturation” thingy in photo editing apps have always been massaging chroma and naming it wrongly.

1 Like

Thanks for your answer. I’ve stolen the thread long enough. I apologize, Boris.

This is a great site with lots of visual demonstrations. http://www.huevaluechroma.com/index.php

For example this one showing the effect of looking a squares with the same chroma in proportional light where they all appear to be the same color however all of them against white will apprear differently …all the basic color concepts are here…

Looking in a similar way at saturation to demonstrate that…

1 Like

I want to move off this post, so I will post on rebooting color balance.

Given the following from Aurélien (at https://github.com/darktable-org/darktable/pull/7347):

That’s confusing because 99% of image processing applications call “saturation” a chroma adjustment (as did the previous color balance).

So, the previous color balance had saturation sliders, but, as indicated above, they were chroma operations, if I understand correctly. In that case, the awesomeness is not new. :slight_smile:

In fact, Aurélien goes on to say:

Saturation actually helps getting deeper colours because they don’t wash to grey but to white, which is more like painting.
[…]
The saturation adjustment gives deeper and more natural color than the chroma.

So, could we say that purity / brilliance is a kind of saturation-preserving ‘brightness’; that is, increasing purity will make the affected area brighter, preserving saturation as long as we stay within the gamut (sliding further away from black along one of the oblique ‘isosaturation’ (as in ‘isobar’) lines); decreasing it will make it less bright, sliding towards black.
In that case, purity might not be the most appropriate term (so I’d vote for the brilliance version), as a ‘pure red’, at least to me, is one that shows no contamination from other colours (such as an orange or purple tinge).

And also (from https://github.com/darktable-org/darktable/pull/7347)

Saturation actually helps getting deeper colours because they don’t wash to grey but to white

So, increasing / decreasing saturation will darken / brighten the area (keeping the same distance from black, increasing / decreasing the angle of the oblique line)?

I never really though about those….I used them to dial in the strength of autopicker hue selections more often than not. They were called saturation but I never really though about them that way just more like strength sliders… :wink:

I was talking more about the global chroma slider and this is clearly doing a chroma correction and not saturation ….the old color balance input and output saturation sliders were I believe doing saturation corrections as the colors clearly deepen and darken or lighten and brighten or what ever terminology you want to use…

Basically to my eyes using global chroma pull out some color and doesn’t alter the luma or the impression of luma too much where saturation has a major effect…

Exactly.

With the ‘old’ color balance module, input and output saturation, I think, does not change perceived brightness, which is consistent with what Aurélien says (‘That’s confusing because 99% of image processing applications call “saturation” a chroma adjustment (as did the previous color balance).’). Chroma adjustment is at constant brightness.
Neutral:


‘old’ color balance at 0%

Color balance RGB at -100%

‘old’ color balance at 150% (neutral is 100%)

Color balance RGB at 100% (cannot be pushed further)

Overdrive
‘old’ color balance output at 200%

Note how the overlapping part of the histogram stays in place.

Compare with:
Perceptual saturation at 0% (neutral):


At 50% (becomes darker)

At -50% (becomes lighter):

Purity at +50% (becomes brighter):


Purity at -50% (becomes darker):

Finally, a purity vs exposure comparison:
Purity (sorry, I reset the history stack by mistake, so not the same as above) at 50, exposure at +0.5EV:


Purity at 0%, exposure at +1.35EV, in split view with the purity@50%, exposure@+0.5EV above:

1 Like

Its a good analysis…honestly I used the CB global sliders most often for contrast which I usually applied first so I think I was under the impression when I used it for global saturation it was a saturation effect…

It does appear the old one was more of a chroma…although I wonder if the algorithm is slightly different as the global chroma slider in the new module seems even better ever so slightly to my eye as you move the slider…It may be I see what I want to see in that regard…

New episode: Capitalism is the virus ☭ :

13 Likes

Very good Boris. I understand that you have used lots of modules as an example of what can be done.
There are some modules (like bloom…) and blending modes that I’ve never used them…
I have enough material to study.
Thanks a lot!

1 Like

Thanks for an excellent video once again, lots of interesting ideas!

1 Like

I appreciate your demonstration of what can be done and how to do it. Valeu! (Hope that’s right.) :thinking:

1 Like

Yes, the greatest potential that darktable offers is almost infinite possibilities of expression and ways with which you can discover unique interpretations of the photo. It is rare to have a tool that offers such variety.

I think it’s a pity that people get scared immediately when the tool doesn’t indicate the straightforward processing they are used to.

2 Likes

Thanks! My approach is having that straight forward edition clear and deviate in some steps :wink:

I think that more discussion on what you can do with darktable as opposed to how to use it would help with that. Your videos in particular and the play raws go a long way

1 Like