Measured after building them, on four of the library's 6D DNGs: Adobe
Standard's tables lower mean saturation by 3-9 % at defaults, and the
look at 200 % lowers it further. The 6D's look table scales saturation
by 0.925 in its darkest value rows; it was tuned to sit under Camera
Raw's default RGB tone curve, which DarkRoom does not apply, and the
dark-tone desaturation is what is left without it. On _MG_9080 the
Lightroom preview measures 0.49, the matrix alone 0.38, the profile
0.35.
So the spec's "that gap is most of why the same file looks flatter"
was wrong: the gap is tone. The tables stay — they put each hue where
Adobe put it — and the spec, D20 and the Vivid file now say so.
"Stronger camera look" is removed: a stronger Adobe Standard look is a
less saturated picture, the opposite of its name. The Vivid presets,
measured at 0.40-0.46 on the same frame, are what answers "more
colourful" today.
The second half of D20: a camera_profile scene operation at order 25
that converts working colour into linear ProPhoto, runs the DNG SDK's
HSV lookup through the HueSatMap and then the LookTable, and converts
back. Hue and saturation do not change under the uniform gains before
it, so a 2.5-D HueSatMap gives the same answer as straight after the
matrix, and the look sees the photographer's exposure as it does in
the SDK. Two departures for scene-referred values: value is not
clamped on the way out, and a colour outside ProPhoto passes through.
The operation holds only the switch (on by default) and a look
strength of 0-200 %. It is composed while the switch is on — a new
Operation::composes() separates "does something" from "moved from the
defaults", so an untouched raw renders through its profile and still
writes nothing. The tables come from the source: dr-gpu uploads the
ones DemosaicedImage carries into a storage buffer at @binding(8),
whose two-entry header tells the fragment whether there is anything to
apply, and binds a header of zeros for every other source.
apply_reference is the lookup on the CPU. The GPU test holds the
shader to it over 256 colours, through synthetic tables strong enough
that a wrong index shows, and through the library's real Adobe
Standard tables when the 6D DNG is present.
The library's Canon 6D DNGs were written by Lightroom and embed Adobe
Standard with its HueSatMap and LookTable; DarkRoom renders them through
the matrix alone, which is most of why the same file looks flatter here
than in Lightroom.
camera-profiles.md designs the deferred half of FR-DEV-3e: the tables
applied by a camera_profile scene operation after exposure, the profile
taken from the DNG or from a matched .dcp, tables carried with the
decoded image like the matrix, a look-strength control, and copying an
embedded profile out where its policy allows. FR-DEV-3e gains item 4
and D20 records the placement and what was rejected.
dtourolle