D-Log M signal mapping for scopes and assists

[erik-sutton95]

Nano (and Action D-Log M bodies) need honest WAVE / zebra / false color / Face Priority math for D-Log M, not Pocket D-Log (2017) used as a stand-in.

Related: Finish Osmo Nano · Start Action 6 · roadmap index

Current mapping (the gap)

ColorMode.dLogM = 0x00 exists and is labeled “D-Log M 10-bit.”

MonitorTransfer.init(_ colorMode:) maps both .dLog and .dLogM → .dlog (DJI D-Log 2017, peak 4200%). Scope ceilings in tree are Pocket live-tap measurements:

• D-Log2 @ native 1600 → byte ~247
• D-Log @ native 400 → byte ~223

There is no Nano D-Log M measured shelf. ISO tables treat D-Log M like Normal (base 100, Auto allowed), which is not Pocket D-Log’s base 400.

Official Rec.709 cubes are in the bundle:

• DJI_Official_Nano_DLogM_Rec709_33.cube
• DJI_Official_Action6_DLogM_Rec709_33.cube

DJI Auto can apply them. Built-in Auto does not. Scopes still linearize D-Log M as Pocket D-Log, so middle gray and clip are wrong on Nano.

Workstreams

1. Transfer type

• Add MonitorTransfer.dlogM (do not keep aliasing to .dlog unless a paper + tap prove they match)
• Encode / linearize from the D-Log M paper used by Nano / Action, not Pocket D-Log
• Wire WAVE, PARADE, HISTO, ZEBRA, FALSE, LIGHTS, Face Priority through it

2. Live-tap calibration

• SoftAP x420-style take on Nano D-Log M: min/max bytes at native EI
• Plug the measured ceiling into ScopeExposureCeiling (same method as Pocket D-Log / D-Log2)
• Comment the ISO used; 255 stays a full-range leak, not 100 IRE

3. Looks

• Built-in Auto: official Nano D-Log M when family == .nano && color == .dLogM
• Keep Action 6 cube selection by camera name (OfficialDJILUT.dLogM(cameraName:))

Do not

• Commit unofficial LUT dumps
• Invent Pocket 4 D-Log M — Pocket is D-Log / D-Log2
• Treat official Rec.709 cubes as a substitute for scope math

Done when

On a Nano in D-Log M, WAVE 0 / 18% / 100 match the paper + measured tap, zebra/false color agree with that, and Built-in Auto can apply the official D-Log M cube.

Concrete threads: Finish Nano · Action 6

[erik-sutton95]

Tracked as maintainer task #84.