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handoff: deliver the tone-versus-geometry split on the title

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The rotation decision needs a size, not just a direction. A per-level LUT fitted
on a screen is the most general tone model possible, so whatever it cannot close
is by construction spatial. Self-fitted, it closes 70.3 percent on the main menu
-- the positive control, where the port measures 0.06 percent so geometry is
right -- and only 32.0 percent on the title. At most a third of the title s
disagreement is tone; at least two thirds is geometry.

Also warns the port off a global tone correction: the curve does not transfer.
Fitted on the title and applied to the menu it closes 29.7 percent; the other way
round it makes the title 24 percent worse.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
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2026-08-29 18:45:30 +00:00
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@@ -805,6 +805,36 @@ one level, parent alpha **0** throughout.
**(200, 90)** against a 399×180 sprite — the pivot *is* the centre, so rotation
displaces it by nothing.
## ✅ 2026-08-29 — how much of `title`'s residual the rotation would actually buy
Measured, because the rotation decision needs a size and not just a direction —
[`title-residual-tone-vs-geometry.md`](../re/structures/title-residual-tone-vs-geometry.md).
A **per-level LUT** fitted on a screen is the most general tone model possible,
so whatever it cannot close is **by construction spatial**. Fitting it on the
screen itself bounds the tone share from above:
| | closed by a self-fitted tone LUT |
|---|---|
| **main menu** (positive control — your 0.06 %, so geometry is right) | **70.3 %** |
| **title** | **32.0 %** |
🔴 **So at most a third of the title's disagreement is tone, and at least two
thirds is geometry** — content in the wrong place. The rotation is the dominant
term by roughly two to one, and the fitted LUT is generous to tone, so the real
geometry share is larger.
⚠️ **And do NOT carry a global tone correction.** Fitting on the title and
applying to the menu closes 29.7 %; fitting on the menu and applying to the title
makes it **24 % worse**. A curve fitted on a dark flat screen is unconstrained at
the bright end and actively harms elsewhere. This extends the single-exponent
refutation: **even a full per-level LUT does not transfer between screens.**
⚠️ Reach: my pairing is looser than yours — same screen, not the same instant —
so the **ratio** is the claim, not the absolute level. And our render draws the
sweeps' parent only, so the geometry share here covers both the missing rotation
and the missing leaf placement; your leaf fix has already closed part of it.
## Status
| | Question | State | Answer / link |