New Sigmoid Scene to Display mapping

Have you tried to edit it with v5 instead of v6 flimic??

Sorry- I’ve been away a few days. So rather than posting more of my own, I’ve been processing some sample raw files from free sources on the web, looking for ones that highlight what I’m talking about. I will post these in another thread soon- I’ve just been busy. In addition I’ll post a src code patch you can use if you are interested.

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I would like to say this is by design. I wanted to make a module that is robust and smooth. This has been approached by having the following: any pixel color should converge to white as the exposure* increases towards infinity. Combine that with the observation that the display gamut is a tilted cube with one corner at black and one at white and highlights will soften for highlights. The available gamut decreases as we approach white.

The “fix” for too compressed highlights is to reduce the exposure of the affected area using either a masked exposure module, the tone equalizer, contrast in color balance rgb, etc, before the display transform.

*I think about exposure here as stops over (or under) middle grey.

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I can happily report that the sigmoid branch has been merged to master now! Looking forward to seeing what you can do with it, hearing your feedback and fixing any bugs that might surface due to it being used more now! :smiley:

And of course spend some time on adding some additional features now that the basics are in!

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Looking forward to testing this tonight. Thanks :slight_smile:

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Hello,

Great, thank you very much and congratulations for your work. :+1:
I will carry out a series of tests and will come back to you with the results obtained :smiley:
Greetings from Brussels,
Christian

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I started a new thread now that the module is officially in the master and this has been a long discussion…if someone thinks we should stay on this one feel free to delete or ignore my new one. I just thought that it will get a lot of interest and it might be nice to have targeted discussion based on this latest and “official” rendition… I have no problem if someone want to delete my thread if that doesn’t seem like the way to go for this topic…

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PR for the sigmoid dtdocs module reference is up. Do you feel like I covered the basics well enough?

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I like it. But it reads a bit like a technical document first, and an artistic description second. Softening it with an anslog-film analogy or something like that in the introduction might make it more approachable.

Also, the very first sentence (“easy to use and robust”) makes it sound like its alternatives are not easy, or not robust. While I don’t necessarily disagree, a more neutral wording might be less provocative.

Speaking of that, I am missing some justification re: filmic. What does sigmoid excel at, and what are its shortcomings? It might be good to explicitly spell that out (very neutrally) in the docs. Probably in both filmic and sigmoid’s docs, eventually.

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Yes that sentence probably won’t make it past the copy-edit (says the guy who does the copy-editing)

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But that is the difference between filmic and sigmoid. In addition, from what I’ve heard, filmic has emphatically not been designed to be easy to use nor robust.

Again and again its authors, devs and users have emphasized that it hasn’t compromised on power and control for the benefit of ease of use or prevention of foot shooting? Have I imagined years of such comments?

You are free to make that comment anywhere you want but subjective statements like that don’t belong in a reference. I’m sure we can find some more neutral wording.

For example we could say that it’s “intended to be” those things, but I have no way to objectively assess whether it “is” or not.

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It isn’t just about being neutral. Terms like “easy to use” and “robust” don’t add value to the text. We aren’t trying to convince readers of something.

What sigmoid is, what it does and how to use it are the things people want to know when referring to the docs. Additional math, diagrams, references, links to alternative modules, troubleshooting notes may reinforce the text.

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I think there are lots of links and math and the curve simulator to play with that can actually plot filmic and other curves is provided and give the background math for the module. There is the statement about valid rgb values for every pixel between 0-inf and the fact that sigmoid does not rely on the concept of a rel black and white only middle grey and this might be the area to clarify in practical terms what that means in terms of making the choice to use this for tone mapping… I think one could say that it provides a condensed simpler UI implementation which may initially be easier for early adopters of the scene referred way of editing to use…

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Looks good to me! I think the first sentence has already been changed, reading the comments above.

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Download the daily built version last night. As an enthusiastic amateur user of DT, I am impressed. As said before, DT gives us many options of doing the same thing. Keep Sigmoid and FilmicRgb separate and give the user the choice.

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Finally playing with sigmoid now 4.2 has been released. It is so good! Definitely becoming my default tone mapper, thanks @jandren !

And a little trick to deal with the lack of contrast that can result in highlights - use a module in multiply blend mode after sigmoid in the pipe, masked to the highlights. I personally like using color calibration due to its flexibility, but color balance rgb or exposure are also options.

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I have not resorted to that yet. I have been happy with using the tone eq to bump highlight contrast and a bilateral preset in local contrast along with an instance of D&S but I should experiment more…

Hi, I have a question: if I have an underexposed pic with a piece of sky that is underexposed so the sky does not get clipped, the first step is to increase exposure with the exposure module. BUT that kills the sky. How do I restore the color of the sky? Is this possibe with sigmoid or do I have to use an additional module? With filmic, this task is pretty easy.
Also, is there a detailed documentation of sigmoid? The chapter in the official manual is pretty rudimentary.

I find tone EQ works really well usually.

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