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Describe the measured tone and vibrance in DarkRoom's own terms

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The calibration commits named DarkRoom's default curve after another
product and described vibrance as doing what another editor's does at
the same value. The curve is the DNG SDK's reference, so it is called
that; vibrance is scaled to deliver the strength its value names, as
measured against the photographer's earlier exports. Two test names
follow. The measurements and where they came from are unchanged.
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dtourolle
2026-10-03 16:41:11 -04:00
parent 7ae1e27810
commit 185e134ead
6 changed files with 21 additions and 21 deletions
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docs/dev/requirements.md
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@@ -2785,13 +2785,13 @@ rendered by DarkRoom against Lightroom's JPEG (MSE, sRGB 8-bit):
|---|---|
| 0.20.0's sigmoid at its defaults | ~1200 — about 0.7 EV darker, and flatter |
| Sigmoid, exposure, contrast and white fitted | ~150 (contrast 1.73, +0.73 EV) |
| Camera Raw's curve after baseline exposure, at contrast 1.4 | 224 |
| Camera Raw's curve, contrast 1.5 | ~150 |
| Camera Raw's curve, exposure, contrast and white fitted | 143 |
| DNG reference curve after baseline exposure, at contrast 1.4 | 224 |
| DNG reference curve, contrast 1.5 | ~150 |
| DNG reference curve, exposure, contrast and white fitted | 143 |
So Camera Raw's curve is the default for every raw, and the default contrast is 1.5 — under that
So the DNG reference curve is the default for every raw, and the default contrast is 1.5 — under that
curve a power of 1.5/1.4 about grey (`REFERENCE_CONTRAST` is where the curve is untouched). The
brightness needs nothing: baseline exposure and the curve together land where Lightroom does. The
brightness needs nothing: baseline exposure and the curve together land where the earlier exports do. The
profile's look strength, vibrance and saturation bought nothing measurable on those exports. The
user chose to change every photograph rather than keep edited ones on the old rendering. The
fitting tools live outside the repository (`darkroom-lrfit`).
@@ -2799,7 +2799,7 @@ fitting tools live outside the repository (`darkroom-lrfit`).
*Amended earlier the same day:* the default was **not** decided. The measurement below was against
Lightroom previews of photographs carrying the user's Lightroom edits — a house look of HSL
saturation (Blue +58, Aqua +50, …), Highlights −40 and Blacks −20 in every DNG's XMP — so it said
nothing about Camera Raw's base rendering. Under Camera Raw's curve `_MG_9080` renders brighter
nothing about Camera Raw's base rendering. Under the DNG reference curve `_MG_9080` renders brighter
than its Lightroom preview (mean 0.39 against 0.31). The sigmoid stays the default; the curve
below is a choice; the default is decided by measurement against Lightroom exports of unedited
photographs (the `lr-fit` work). What follows is the original text.