New Sigmoid Scene to Display mapping

Going by @dirksagwitz’s samples only, filmic appears to have normalized brightness and regional (compared to global or local) contrast compared to sigmoid.

I won’t say anything about colour shifts as my system isn’t colour managed and both methods have their own challenges…

Just looking at the whole images sigmoid looks good (if a bit contrasty) and filmic looks strange.

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funny I would use a bit of tone eq for the sigmoid one esp for the left hillside and then overall I like the sigmoid better in this case if that change was made…I do like a bit of contrast maybe that is it when I look at it…

I would really like to give this a try.
Has anyone built a Windows version? If so, any chance you could share it?
Thanks :slight_smile:


So nice to tackle other pictures than my own and it also gives me the opportunity to introduce a slider in more detail: skew!

Think about skew as a way of prioritizing contrast in your image. Positive skew increases the contrast in the highlights while reducing the contrast in the shadows. Negative skew does the opposite. But let me show it in images instead of words! The following three images are my try at editing your image using a strict scene-referred workflow (more on that later). The only difference is in the setting for skew: 0, 0.39, and 1.

Pay attention to the clouds!

Skew = 0

IMG_7253_07.nef.xmp (42.2 KB)

Skew = 0.39

IMG_7253_08.nef.xmp (42.9 KB)

Skew = 1

IMG_7253_09.nef.xmp (42.6 KB)

As you can see, adding a bit of positive skew can make those highlights pop a bit more!
It is actually quite pedagogic to take a look at the histograms for these as well. Note how the right white part (the clouds) gets pushed to the right.

Skew = 0 Skew = 0.39 Skew = 1
histogram_skew_0 histogram_skew_039 histogram_skew_1

Some notes on editing

Try to figure out how to put all your modules below the display transform (filmic/sigmoid). This is especially true for dodging and burning highlights and shadows as this operation is a simple multiplication when done in scene-referred space. I personally love to work with masked exposure for this effect and then complementing it with the tone equalizer when there are tricky edges I don’t want haloing around. This is a learning process for the whole community so I will try to help out as much as I can on the topic.

The new color balance rgb module works very well for me and it’s good to see it in use by you as well. One module that is yet to be “ported” to the scene-referred space is local contrast and I see that you correctly put it above the display transform. But, I have found that it actually works ok to use it earlier in the pipeline and I have been especially successful when applying it before adding saturation using color balance rgb. Might be worth a try while waiting for a rewrite of that particular module :wink: One more trick when it comes to local contrast is to use the parametric mask and only apply it on your highlights in scene-referred space.

Highlights are an interesting topic as we still do not have that many specific tools for editing them in scene-referred space, while also being the image feature that differs the most in editing possibilities when in scene-referred compared to display-referred!


I have a dropbox link on the FB page…with some instructions as well…

basically just unzip it where you like. I have a bat file in the directory that will run it from wherever you unzip it and will use an internal config directory in that folder so it won’t interact in any way with your current stuff…

Just take care as your xmp will not be compatible with standard versions as they don’t have that module…

EDIT so make a shortcut to the bat file by right clicking and add that to your desktop


I found the tone eq worked nicely with your module. I like the contrast in general that your module generates but usually the shadows need a bump and the highlights need pulled back so a basic sine wave spline in the tone eq was a nice fix…

Here another example. A shot I took two weeks ago.

Licence is: Creative Commons, By-Attribution, Share-Alike

Stork.cr2 (22.7 MB)

filmicrgb (standard settings + 1 EV, crop)


Stork.cr2.xmp (8.3 KB)

sigmoid (standard settings + 1 EV, crop)


Stork_01.cr2.xmp (8.7 KB)

First of all: The stork’s neck feathers where almost white, not somehow pinkish as in the filmicrgb example. In this case, setting filmicrgb’s “middle tones saturation”=0% and “preserve chrominance”=no helps. All in all sigmoid’s colours look more realistic for me, expecially the reds, e.g. in the color of the beak.

But if you look at the structure of the white plumage at the neck and head, filmicrgb delivers more detail imho.


@jandren thank you very much for your hints and suggestions. I did some additional image edits with the sigmoid module … and I like it more with each edit I am doing :slight_smile:
Now I will play a bit with the skew parameter, too. I am quite sure that this is a very powerful module and for sure a great alternative to using filmic. In my opinion it should be integrated into Darktable very soon.


I had exactly the same impression, but I suppose playing a bit with local contrast and the skew parameter may produce similar details as filmic does.

With @jandren’s explanation I’ll give skew a chance, too :wink:

I bet a couple of turns on the scroll wheel in the tone eq on the neck will bring back some detail…Its just exposed more in sigmoid it seems in the highlights…


I left this image here for your test. It’s all yours, hope to see the results using the Sigmoid module.

Creative Commons, By-Attribution, Share-Alike

This is the .jpg directly from camera. I shot the jpg using a modified Fujifilm recipe.


DSCF7042.RAF (48.0 MB)


Test it on

Note that it seems the pink cast was present even before filmic:
With exposure and filmic:
With exposure and filmic turned back on, but no saturation boost in filmic:

A filmic-based rendering (history in the jpg), with highlights neutralised in color balance rgb


Thanks @kofa, imho your examples confirm that the pink becomes visible / disturbing with filmic switched on. And, yes, this effect can be reduced if you switch off “saturation boost” boost (I called it “middle tones saturation”). Filmicrgb in the hands of an experienced user is very flexible and fine-tunable, no doubts.

The point is, that sigmoid doesn’t need this tweak at all to show more natural colours.

I merely wanted to point out the filmic was not ‘distorting’ or ‘inventing’ colours: those feathers were pinkish even before you reached filmic. I don’t doubt that it was easier to reach the desired look with sigmoid (which is something I really anticipate having in darktable), but that seems to come from sigmoid desaturating highlights more, which may affect other pictures adversely.


Here’s what I get. All standard settings, no tweaks, highlight clip indicator on:

original, no tonemapping



To be fair: filmicrgbs result without the annoying :wink: clip-indicator looks absolutely ok imho:

Edit: upload correct screenshot #4