Making sense of tone curve/tone mapping/exposure tools in RawTherapee

Adjusting Tones

I’ve been studying the RT Exposure tab in an effort to better understand my options (and possibly contribute to the docs, or make some tutorials). From my reading and experiments, I think many of the tools offer different ways to manipulate the tone curve. i.e., you could accomplish basically the same thing through manipulation of the tone curve, or combining one or more of these tools:

  • auto-levels
  • exposure compensation
  • black
  • lightness
  • auto-matched tone curve (maybe?)
  • tone curves
  • shadows/highlights
  • LAB adjustments (which limit the impact on saturation)

If that’s accurate, then you could in theory categorize each of these tools according to the nature of the control they give you. e.g., flexible tone curve if you want complete granular control, vs a parametric curve or sliders for more gentle/smooth adjustment of particular tonal ranges.

1. Does that make sense?

2. Tone Mapping

If this does make sense, does Tone Mapping belong to this continuum, or is it doing something fundamentally different? The description in the manual seems to suggest it’s doing more than just adjusting the tone curve.

3. Tone Equalizer

Same question for Tone Equalizer, which seems to be doing something similar to a parametric tone curve, but doesn’t have any explanation in the manual.

Tone Equalizer was first introduced in ART (I think) and here is the author’s brief explanation (scroll a bit down):

https://art.pixls.us/Reference#markdown-header-exposure-tab

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