The tone mapper your granddad would envy I: request for help with the data

Software darktable
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As some of you might have noticed, the focus of my tinkering with true to physics LUTs shifted to trying to create a tone mapper attempting to purely implement what film and paper does. Currently grabbing a lot of good ideas from spektrafilm. This is what it currently looks like:

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The next step is long and tedious, and even though a lot of it was already done, it will take me ages alone. So I want to ask for your help to move this forward.

I’m extracting data from film and paper spec sheets. Collected them here (thanks to 125pix.com).

The results are here and the code doing the work here.

Yes, the code is all AI slop, I’m in the let’s get shit done mode, not in the write beautiful monadic code that can be shown on functional programming symposiums mode :slight_smile:

Anyway, I’m at the stage where I would start going through it one by one and yelling at the AI if something is missing. The debugging mechanism is based on generated data overlayed over PDF content, saved to an image file. Like below. As you can see, apparently we are not generating data for one of the charts.

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point is, I need the chart data extracted. What I know I need for now is

characteristic curves, spectral sensitivity, spectral dye density for color film. for black and white, spectral sensitivity, characteristic curves. For paper, again, characteristic curves, spectral sensitivity, spectral dye density.

Problem is… this starts feeling like it will take a year if I do it alone. Wanna help?

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One question: what are you trying to do here that is better or different from spektrafilm?

The fact is that asking people for help doesn’t seem very fair when it seems the understanding of the end goal isn’t really there.

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This didn’t start as a spektrafilm clone. That I’m lifting ideas from it now is kinda incidental. That doesn’t affect the legitimacy of your question, just saying.

I guess from the practical standpoint the win here would be that you have access to this at the end of a pipeline where all the darktable goodness preceeds it.

Sure, you can do completely “raw” film reproductions, only having exposure and the emulation enabled, and in that case you might indeed be better off with spektrafilm.

On the other hand, If you would like to use diffuse or sharpen, color balance rgb, tone equalizer and the rest of the tools that give you the results you already love, on top of authentic film look, yeah, that would be the unique selling point here.

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Why not help spektrafilm ingest more film stocks, e.g. why not work upstream?

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The darktable/Spektrafilm workflow is rather tedious, so I really understand the wish for a Spektrafilm style module in darktable. It’s currently my greatest wish for darktable too. :slightly_smiling_face:

This module (or other new modules) would ideally also bring support for other film properties like halation and better grain. The monochrome only grain of the grain module will not do (as I see it). If this is done as an update to the grain module, we also have the problem with module order. Grain should come after upscaling, which darktable currently doesn’t support.

I remember @hanatos saying that implementing Spektrafilm in darktable will be too slow.

An idea is to go the Resolve Film Look Creator path which doesn’t try to simulate any specific film stock (or paper), but gives you the ability to develop new “film looks” (with grain and halation etc).

The work @Christian-B is doing with 3DCF seems related.

For me it would be the ability to do dodging and burning without having to export a new linear 32 bit image for every new adjustment I do in darktable.

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There is a new darktable module proposal Spektrafilm darktable module sort of
but it is not a PR yet.

Implementing this on my homemade build on macOS was easy (just remember to take the dev branch of spektrafilm), and now I have spektrafilm fully integrated in darktable. Now playing with it …

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Oh, great, seems like I’m dupliating the effort of someone who might even know what they re doing. One way or the other, I hope something’s gonna land in darktable, other than classic looks, I would also love to submit my color work to the creative constraint of “ok, this is what ektachrome looks like, leave it alone”.

Just one question: does your work also position your module as a tone mapper? My understanding is that that would be the place in the pipeline for something like this, rather than some effect on top of AgX,Filmic/sigmoid.

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It’s meant as a tonemapper replacement yes. And I wouldn’t go so far that I know what I am doing but it seems to work for me :smiley:

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