A blown out sunset, I think the preserve hue slider is really the way to go for handling these color reconstruction issue ; one side is too yellow, the other one two salmon, but there’s a sweet spot in between that would hard to reach with only discrete options.
3 Likes
Toggling luminanceY I’m not bothered with with filmic. Depending on the scene , i decide if highlights to white or to be colorful is what I want
In filmic that means switching between max-rgb and luminanceY. With sigmoid , that means toggling between two modes .
With some more testing on playraws, i do notice that filmic can have a bit more of an issue (often) where there is a crossover between bright spots unclipped , and bright spots reconstructed highlights.
Sigmoid does this smoother , which can hide some details but fixes the need to fix the crossover point.
Maybe i dont notice this in my own shots as much , because i didn’t clip , OR (because I’m not perfect 
) my preprocessing in DxO causes dxo to reconstruct the highlights… which is often smoother but worse than DT methods.
Since DT recently got the ability to do some kind of HLR on rgb data (so i paint opposed works ok linear DNG for example ) I’m retrying a lot of shots with that combo… Maybe i should try sigmoid in images where i still use a tiny bit of filmics reconstruction to smooth over boundaries with HLR
I think any and all shared tips images and discussion of the results are really good. You bring up a key point…when you say for your shots…so many people will have a style that might consistently push some boundaries or have subject material with some unique requirements that might push or reveal strength and weaknesses in each tool…
Because of easy of use and straightforward application of the sigmoid module I can see new users being more comfortable with it and experience users may also appreciate that and then use filmic’s extra tweaking or perhaps HLR in certain situations…
And then some might have spent so much time with filmic they have their settings well in hand for how they edit.
I think sharing tricky images and workflows for both is a really nice set of examples for everyone to appreciate and learn from…thanks to all of you that have posted and continue to post…
That is a really nice solution! I like it. It pretty much solves the issue that I was experiencing. I see myself using sigmoid probably a majority of the time and filmic for when I really need/want the extra control.
Same, I do like just to adjust it to taste when needed. There are also a lot of images where the preservation operation is unnoticeable, and it doesn’t matter what you put it to. What value did you end up with for this particular image?
and
These two observations about the loss of detail in highlights and better looking bright check nicely sum up the difficulty for a display transform. Those two requirements are competing with each other, and I think it is impossible to solve that problem without taking the local context into account. Neither filmic nor sigmoid does that; both are per-pixel-based in their operation. So you have two options to bring out more details in a bright area, either dodge it with a local edit or increase the local contrast.
This brings me to:
I think it would be even better to add the local contrast adjustment before the display transform module. D&S is the option at hand today, but a modernized local contrast had, in my eyes, been a very nice addition to darktable!
Nice to see your experiments with both normal daytime images, sunsets, and epic landscapes!
About a recommended workflow, I will try to use the discussion in this thread as a baseline for writing them later on. There are multiple methods to get to the same point, but two possibilities are the following:
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Activate and forget. (Default settings, contrast=~1.5, skew = 0, per-channel, hue preserve=50 or 100%) Do all the editing in other modules. The big difference to the recommended filmic workflow is that you will need to actively use the color balance rgb contrast slider to tweak your contrast setting.
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Sigmoid contrast as a start. Same settings as above, but after finding the mid-tones. Tune the sigmoid contrast setting until you are close to satisfied/“neutral” with the saturation for your mid-tones. Then work with other modules as you normally would. Adjust hue preserve to taste. Skew will be part of the equation but try to save it for later in the editing (my gut feeling here).
Those are my two most used approaches so far. There are more possibilities.
The short answer is no. Both assume that the input data is unbounded, and both give a bounded output. Sigmoid would, in this case, not become very white (converging to white requires large values on the input, larger than filmic ever will output). You may, however, apply both in parallel and then blend the two results together. Sadly not supported in darktable, but export both images and then blend them in Gimp or whatever. A node-based image editor could make crazy things like that doable.
8 Likes
I tried the Sigmoid module on the Sunflower Sagas and Solutions play raw. The file is here at 0L0A3314.CR2 (33.3 MB)
The Filmic Version:
0L0A3314_09.CR2.xmp (12.8 KB)
And the Sigmoid version:
0L0A3314_08.CR2.xmp (8.9 KB)
Sigmoid settings were close to out of the box, except I found the RGB Ratio under Color Processing gave the best results:
I found with Sigmoid I was able to bring out glow and contrast to the flower’s petals, which was something I struggled to get with Filmic. As a whole I seem to get brighter colors and contrast when using Sigmoid. This looks very promising.
5 Likes
I went for these…
With 1 EV exposure…
Bold I guess but I like it… 
I really need to calibrate my screen…this looks much paler after exporting than on my display…
Not one of my best shots, it was extremely sunny at Loch Rannoch, so the range is pretty high.
Here is the original image, and the developed images with their sidecars. The original sidecar is Sigmoid and the “1” sidecar is Filimic.
20221103_0015.NEF.xmp (11.7 KB)
20221103_0015.NEF (51.9 MB)
20221103_0015_01.NEF.xmp (12.2 KB)
These files are licensed Creative Commons, By-Attribution, Share-Alike.
3 Likes
To follow up my post from a few days ago, I have one of the sunset images I tried with Sigmoid. Not a great shot overall, and not edited to look it’s best, only to show what I get Sigmoid to do. Highlight reconstruction is with Inpaint opposed in both cases, and this camera (Canon 550D) requires the clipping threshold to be set at 0,847.
So here is the one with Sigmoid:
Marokko_0066_01.CR2.xmp (10.7 KB)
Perfect gradation outwards from the white(ish) sun, just the way I like it, with a reasonable amount of yellow before the orange, and no clipping or banding, at least on a reasonably good monitor.
And here is the best I could get with Filmic V6:
Marokko_0066_02.CR2.xmp (8.1 KB)
Too much desaturation around the sun going directly into salmon pink.
Filmic V5 Gives a slightly better result, but here I have to tweak both white relative exposure in Filmic and highlights saturation in Colorbalance RGB to get a nice yellow, and the gradient outwards from the sun is still not as good as with Sigmoid, even with much more work:
Marokko_0066_03.CR2.xmp (9.8 KB)
All of these also have the standard basic colorfulness preset applied in colorbalance rgb.
And here is the raw file, if anyone wants to try:
Marokko_0066.CR2 (19.8 MB)
These files are licensed Creative Commons, By-Attribution, Share-Alike.
I haven’t tested much with more day-to-day images under different conditions yet, but I’m pretty shure I will end up using both Filmic and Sigmoid in the future. They are both great, with their own strengths and weaknesses, and they will both be the best for different situations.
9 Likes
Another very nice-looking sunset picture!
Maybe I should have called it “the sunset module”…
11 Likes
Yes a modernized local contrast (i.e. local contrast RGB) would be great! Is anyone working on it? Similar to what vkdt has currently works great.
1 Like
So here is a comparison of my exp build with the gamut_check_RGB() calls disabled in filmic v6 to sigmoid. I’ll try to post exp files later maybe, but I have them disabled for the moment so I don’t mess up by normal dbase. But I’ll show the only differences between the two complete edits- there are only 2 module changes, including sigmoid.
With sigmoid I was able to get VERY close to what I consider the best renders I’ve obtained using the experimental build of mine.
If you start from my original xmp, and open using the master (11/05) that includes sigmoid, the changes I made are as follows-
filmic v6: off
sigmoid settings:
Now this makes the colors and details look the way I want, but it tends to sabotage the contrast in the shadows as a trade-off. After experimenting I found that the tone equalizer could be used to get it to look almost the same as my original edit. Here are the tone equalizer settings:
And here are the two edits-
My original “best” using my exp build with the gamut_check_RGB() calls disabled:
And here is my edit using the master (11/05) with sigmoid and settings I described above:
It looks pretty good IMO- encouraging!
Lots of crashes unfortunately with this build but not necessarily having anything to do with sigmoid- seemed to happen a lot while tone EQ was being manipulated.
5 Likes
That looks very nice. The developmental build does seem to slow down and lag, with export rendering taking a lot more time than usual to complete. Hopefully that will get sorted out
Nope! Still, we might find a better name.
1 Like
If you have an AMD graphic card, today was merged a fix that was making it crash. Fix NaN in gamma.c for AMD graphics cards by piratenpanda · Pull Request #12780 · darktable-org/darktable · GitHub
Thanks @hannoschwalm for help fixing it
2 Likes
So that’s the salmon effect people talk about with filmic. I’ve never noticed it my own shots. But I’m not much of a landscape guy.
Very eager to play with it , see if there is a reason i didnt notice it, or it’s just my pictures or something.
At the moment my household is up in shambles by a sick baby for weeks… So all time available goes towards trying to sleep and getting some work done … Looking forward to toying around with the sigmoid demos here!
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Yeah there are some performance issues … Thumbnail generation taking longer, preview pipe seems to take long or keeps on processing , making exports slower .
It’s being worked on / investigated .
But maybe rebasing the sigmoid branch on a 4.01 release and using that for testing gives a nicer experience.
I regularly compile master with some of the ‘experimental braches’ to toy around .
But segmentation based crashing and the pixel pipes slowing down makes the latest master builds a bit of a hassle compared to a few weeks earlier.
That’s no complaint of course ! That’s development and bleeding edge for you:).
But there are such nice darktable toys these months that i want to play .
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All performance issues related to opposed are due to a) no opencl code yet and b) all code before demosaic uses all data and not only the roi. (THIS is new since a month or so, takes cpu cycles for quality) Crashes should be fixed…
Sigmoid has no CL code too yet.
4 Likes
This one and any many other sunset transitions (to blown out) look very smooth. Wish there was a an option to bloom from the blown out portions (as in filmic). Perhaps for the next version. This brings me to the question: will there be “version management” like in filmic? I.e., will there be a color science v1 for sigmoid in the christmas release?