A tone equalizer in darktable ?

Excellent! I am happy to test it!

Excellent … I have been so looking forward to this!

Congratulations, great work. Looking forward to try it once Pascal merges my fix :wink:

Compiles fine on Windows 10.
Testing it, it seems to work, but…
On pictures taken in bright sunlight, with quite high dynamic range (main histogram spread end to end), the tone equalizer histogram covers only a small portion of the luminosity range

Cattura3

which leaves very limited room for adjustments, only 2-3 sliders / points have an effect.
What’s going wrong ?

Marco

I’m getting the same issues with all my pictures that have an histogram stretch from left to right in the main darktable histogram while the histogram in tone equalizer is compressed on the right side with only 3-4 sliders effective.

I will post a screenshot tomorrow when I have access to my Mac.

Nothing is going wrong. The guided filter is applied iteratively 2 or 3 times on top of itself, depending on the preset you choose. Depending of the feathering factor used, the guided filter tends to average the luminance piece-wise, thus compress the histogram around the average luminance of your picture.

Screenshot_20190924_110347

To compensate for that, in the masking tab, you can use the mask exposure and contrast compensation. The exposure compensation will slide the histogram to the left or right, and the contrast will dilate/compress it around -4 EV. To help you setting them, you get a bar representing the histogram spreading just above those settings. The bright bar represent the coverage of the first and last deciles of the histogram, so you get 80 % of the histogram in it. Orange highlights appear when a part of the histogram is outside the tone equalizer settings range.

You get auto-tuners to help you, but they work well only when mask quantization is set to 0.

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1h45 of explainations about how to use filmic RGB and the new equalizer in a no-nonsense workflow. Also, my first video in English.

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Thanks for all your efforts(and time)! :slight_smile:

Great English skills, Aurélien!

Merci, Aurélien!
I am only recently starting to play with the filmic module and look forward to watching your video.
Thank you for all the time and effort you contribute to darktable.

Actually, I’d like to thank all the developers of darktable, both past and future.

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Very interesting even for a non-darktable user!

I somehow missed the fact that we can now re-order modules in dt. Good news! And congrats Aurelien on a very informative and approachable lecture about image processing and the upcoming features.

Great video, I’m only part way through it, LoL.

I appreciate that, for some, module reordering is a nice feature but, in the video, you comment on how some modules should be above/below others with an explanation but the explanation is above my level of understanding. I have neither the photography nor image processing knowledge to change module order with any real understanding of the implications. Will the default order be sufficient for basic users? Will there be an option to reset the module order to default if I should accidentally (or on purpose for experimentation) change the module order?

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Right. I need to do another video on that.

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Thanks a lot indeed!
I have just watched your video tutorial and there are plenty of interesting tips :slight_smile:

Do you accept donations and if yes how? Paypal?

You need a better microphone! :wink:

Yes, Paypal. Thanks !

I recorded with this baby, I think it’s the encoding that is mostly faulty here.

I have at least got time looking at the video. Thanks, that clarifies some parts especially on masking.

I watched this yesterday and found it fascinating. Like all good teaching though, it provoked lots of new questions. I hope these aren’t too silly:

In the section on Filmic, I was interested in how difficult it is to automatically choose a black relative exposure, because the noise is not really distinguishable from “signal”. As an X-Trans sensor user, I experience the auto setting failing most of the time, for that very reason. One question came to mind - is there any useful information in the noise profiling that has already been done for the profiled denoise module, which could give Filmic hints about where to set the black exposure at different ISOs for different cameras?

In the Tone Equaliser section I could see how powerful this tool could be, and I can’t wait to try it out. However I’m still confused about how the mask created by the guided filter relates to the points in the image the user selects. Let’s say I am editing an image, and I want to darken a cloud in the sky. I hover over the cloud and apply a -1EV correction. Does this mean that the same correction is now applied to all points in the image that have the same brightness in the mask image as the selected location, with reduced effect where the mask brightness is different?

Thanks for any answers, or explanations about how wrong I am!

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Yes but no. As I said “black” is merely a clipping threshold between valid data and garbled noise. It depends on the sensor noise level, but also on the actual dynamic range of the picture (having a 14 EV-capable camera does not mean all your shots have 14 EV dynamic range) and the settings you define in darktable, in modules coming earlier than filmic in the pipe (because it’s a full streamlined pipeline, and not independent modules, people often forget that). All in all, sensor noise data are not that relevant at this point of the pipe.

Exactly. You would need to use drawn masks in the exposure module to get exactly the same effect but on spatially-defined areas. The tone equalizer processes all the pictures, just caring about the original exposure of pixels, and performing a pre-filtering (is the option is set) with a guided-filter to get smooth exposure zones to avoid local contrast losses.

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