Evaluate the new sigmoid tone mapper just merged into master ...

I thought it might be time for a new thread on this topic as the old one had a grown really large.

Feel free to think otherwise and use the original one…

Now that the module will have a wider audience and is open for field testing I invite people to post images that demonstrate success or failure with the module and therefore provide some targeted feedback before the official release comes in Dec…

Given all the recent work on HLR it might also be nice to see how it works with that new code??

Now merged…

EDIT…for those landing on this topic here is the original…not hard to find but here it is anyway

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Some quick edits. I like how good it looks out of the box and it’s very easy to adjust. I’ve read a lot of the discussions but still don’t understand it enough to comment on the technical aspects.

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Taking the image from this post I feel it does a nice job… These sorts of images have often been hard to manage. With the sigmoid curve module the default is to preserve the hue but there is a slider to dial this back…in doing so with this image you can go from 100% which is a bit more of the reddish hue at least perceptually and slide along to zero where you get the yellow…in between you can hit a nice mix. The second option with no slider seems a bit like filmic v6 set to no or luminance… but this simple slider to cover a nice range of yellows to redder sky lets the user land on what they like…maybe not accurate but then we have filmic and all its nuances as well is this simple one doesn’t meet what is needed…

So simply taking this image and doing an auto exposure for 50% which lands around 1.8 EV … I get this by default…

At 50% preserved

And at 0 you can see yellow

I think I stopped around 35-50 % on my screen for a nice balance or pleasing image to my eye…

Tweaking the skew and zeroing preservation as in the provided preset…really brings up the yellow…

So it will be interesting as more people try it on their images giving them issues with the current tools and see how it compares…

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That’s a great example… Based on your examples the closer to 0 do look a lot better… I have faced those issues with filmic as well in some of my pictures. It’s good to know there’s now an alternative that gives desired results without much fiddling.


I also like the default look and colors. Instantly much better than what I achieved in filmic but this might be due to my own incompetence

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Very impressive immediate results as well as controls. Failed to compile on my workstation Debian Sid so just testing on the laptop for now.

Only initial strangeness is that some images, perhaps night time/underexposed ones, turn a sort of magenta-reddish haze. It’s a bit as if white balance changed. Anyone else?

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Basically what I said here need help for correct colors - #24 by sgotti

You get better pleasing (also if personal, but for most users) results with sigmoid with just few operations.

You answered that you can do the same with filmic but has you have now also noticed, the default hue preservation doesn’t use a norm based algorithm but an algo similar to the so called “film like” algo of rawtherapee and has a slider to choose how much to preserve. @jandren explained it better in the original sigmoid thread.

I’m not saying that we should make it the default but with a simple style where you enable sigmoid with its “aces like preset”, lens correction (btw there’s a new metadata based method just merged in master: iop/lens: add embedded lens metadata correction by sgotti · Pull Request #12714 · darktable-org/darktable · GitHub), the new highlight recovery and perhaps a bit of “color balance rgb” and call it newcomers you’ll make a lot of new darktable users very happy :blush:.

The fire flames will be yellow and not white, the skies will be colored, the faces will be healthy and users will be happy. From that point they’ll have all the time to study the manual.

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Forgive my very dumb question. Is this a new module coming to DT in the near future?

@Terry It’s the “sigmoid” module available if you compile from git master (or wait for some user provided builds) or in the upcoming darktable 4.2 that should be released the 21 December 2022.

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OBS snapshots from the master branch PPA worked on Jammy, no need to compile.

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Thanks for all the hard work building new modules and solutions for DT. I look forward to seeing it in one one the weekly builds or Windows.

It can still look a lot like filmic on some images esp at 100% preservation or using rgb ratio but the sliding scale of preservation with just contrast and skew to tweak a little do make it pretty easy to get something that should please most people…

With skew and some contrast you can deepen the colors or relax them and get a more desaturated look. Its compact and fairly predictable from my limited experience.

I did find on few that the basic colorfulness preset for rgb CB could actually make things look worse. It may be that doesn’t really need something like this as a rule but rather just color grading from the base it offers… Like most things DT there is a recipe there you just have to experiment for your own personal taste…

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SooC JPEG

With Sigmoid

With Sigmoid and color calibration auto picker

Really nice addition to darktable, looking forward to the next release.

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The new module does provide fine results with minimum effort. Filmic does allow a more custom look and I do like the graphics that it provided. I think that it is useful to have the information on the dynamic range of an image.
I will be quite content to keep with sigmoid as a standard but maintain filmic for special occasions.

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Just installed the new nightly build.
Sigmoid seems very good. I’ll keep using it for a bit and see how I go compared to filmic, which I don’t usually have many probs with, but the new module seems very quick and easy to get nice results. In this image I just used wb, sigmoid, d&s and color balance rgb - the last only to add a little blue to the shadows, not saturation. All the color is just from the sigmoid per-channel processing… I wonder if this could be a problem for things like colour grading consistency - not I do much of that.

But then, one could just switch over to filmic, or indeed the sigmoid rgb ratio option which seems much more like filmic in output.
I think for a nice starting point for quick adjustments, sigmoid should be absolutely terrific…
DSC_8974.NEF.xmp (7.6 KB)

Another benefit of the sigmoid module is that for batch processing it doesn’t need the white and black relative sliders adjusting - cause it doesn’t have them:slightly_smiling_face:

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No you still will need to tweak skew and contrast if not you really lose a fair bit of highlight detail…look for images with rocks or whatever in the sun or light… turn it in and off you will see that compression kick in so you need to tweak that a bit but I think in the end a bit less fiddling

Not sure I agree with either the name or the conclusion:

  • it shouldn’t be just for newcomers, but a valid tool for all users;
  • if the new users are initially satisfied with the processing, they will not start looking at the manual, because they don’t need it;
  • if the new users are initially not satisfied with the processing, they will not start looking at the manual, because they will think the program is bad, and just leave;
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Tried it a lot lately, just before it got merged.

I kinda keep falling back to my points i initially had .
I don’t like how it turns to white quickly in te highlights . And if i want that from filmic , i just set it to luminanceY mode.

The other mode , that doesn’t turn to white but keeps color in the highlights , is nice. Don’t get me wrong . But it seems to give me nothing over filmic max-rgb.

I even had a while with it set to default instead of filmic … And always ended up putting filmic back.

I thought it was only me. Truth be told, I only did a quick test yesterday, with images taken on our latest walk, under hazy conditions.
The skies, for me, under those conditions, have less detail, and less colour than filmic, no matter what I do. Also, I find it strange that I cannot set the white point: I have to increase contrast to fill the histogram. Yes, I know, photography is not about filling the histogram, but to make use of the limited dynamic range of the display, I think, for most images, not stretching the histogram is simply a waste.

@priort
I may post a couple of images with the raws. Should I post them here (’ I invite people to post images that demonstrate success or failure with the module’), or as play-raws?

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