luminance/lightness channel preview for setting exposure, compare to theme?

Software darktable
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1

The manual recommends getting mid-tones right for scene-referred workflows first. I have also read that darktable-elegant-grey is near middle-gray so it is useful as a comparison.

I have a couple of questions though — apologies if they reflect some misunderstanding.

  1. Are we talking about the J channel?

  2. Is it possible to preview the lightness of the image (the J channel) directly while adjusting exposure? I am aware that I can open the parametric mask controls and press c over the relevant channel, is it would be useful to just view that while adjusting exposure.

  3. Which part of the theme should I be comparing middle grey to, the area surrounding the image in the darkroom?

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Revisiting this question: if I want to visually assess exposure with a direct visual comparison of the reference mid-tone, would it make sense to

  1. turn on color assessment (Ctrl-b),
  2. set mid-tones saturation to -50% in filmic rgb
  3. and compare the background to the resulting monochrome image?
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3

I just use the color picker…with live sample…and click to expand the swatch…it ends up being right next to the border so you can compare or adjust pretty easily

So normally you see this

image
image1454×764 219 KB

But if you click the color sample expands against the border and you can just sample and adjust as you like…

image
image1020×751 152 KB

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4

Why do you want to compare your midtones to the background?
Getting mid tones right is about getting those exposed as you want to end with - if your midtones should match 18%grey, you can do this. If you like to brighten or darken them later, do it in this step, not later.

The intention of the recommendation is: set exposure of your main object (most are taking photos of objects, not midtone values) to match your expectation (the black cat isn’t 18% at all)

RAW processing isn’t about counting numbers :wink:

5

The gray background that surrounds the white frame in the color assessment mode.

6

Where / how do you click to do that?

7

If you right click anywhere in the image while the picker is active in area mode, then it expands to cover almost all of the image.

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8

For the example I showed you it happens if you just click the small patch…it’s like a toggle click to expand click again and it will go back

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