Built-in Sweet Spot LUT (Cullen Kelly concept)

[erik-sutton95]

Add a Sweet Spot look to Built-in LUTs, inspired by Cullen Kelly’s Sweet Spot exposure tool.

Sweet Spot is a commercial LUT. We will not redistribute Cullen’s files. We author our own cubes (or a GPU look) that implement the published idea: show the band around middle gray and let the rest fall toward gray.

Concept (public description): isolate the part of the image between about ½ stop below mid-gray and 1 stop above; everything else desaturates / goes gray so you can see whether the subject sits in that exposure band.

Related: D-Log M mapping · Pocket grading · roadmap index

What already exists

• Built-in Auto: Pocket D-Log / D-Log2 Rec.709 cubes
• DJI official Rec.709 cubes including Nano + Action 6 D-Log M
• Custom .cube import
• No “Sweet Spot” string or look in tree
• Nano Built-in Auto is currently off

His published set covers LogC3/4, SLog3, Log3G10, Apple Log — not DJI D-Log / D-Log2 / D-Log M. We would be building Pocket/Nano versions anyway.

Workstreams

• Author original 33³ cubes (or a shader) for D-Log, D-Log2, and D-Log M using our LiveColorScience mid-gray + stop math
• Built-in picker row: “Sweet Spot” (credit the concept in Operator Setup help, not as an official partnership)
• Toggle vs Rec.709 look — this is a metering look, not a delivery LUT
• Legal pass: original work, no bytes from cullenkellycolor.com
• Hardware check: skin at 18% lights up, blown sky goes gray, Rec.709 delivery LUTs remain a separate row

Do not

• Vendor a downloaded Sweet Spot .cube in ios/OpenPocketCine/Resources/
• Replace Built-in Auto Rec.709 with Sweet Spot (operators still need a picture LUT)

Done when

Built-in options include an original Sweet Spot look for the log curves we actually shoot, credited as a concept, redistributable under this repo’s license.

[erik-sutton95]

Tracked as maintainer task #96.