docs/re/structures/title-residual-tone-vs-geometry.md validates its per-level-LUT
instrument with a positive control on the main menu, on the grounds that "the port
measures only 0.06 % of pixels differing, so geometry is essentially right".
That 0.06 % is verify-capture's, and it counts pixels differing by more than ~64
levels -- a gross-displacement detector. It is blind to sub-pixel offsets and
antialiasing differences, which are exactly what a per-level LUT also cannot close.
Measured: after the LUT, the menu's remaining residual is 6.94 on edge pixels and
2.20 on flat ones, 3.2x. Known negative -- render vs itself under a pure gamma --
leaves 0.00, exactly, because a per-level LUT inverts a per-level effect perfectly.
So the concentration is spatial and the menu is not a geometry-free control.
Their conclusion survives: the title's 32 % never depended on the control. The
refutation is of the validation only, and I say so.
The half that is mine: verify-capture's header now states what the diff column
thresholds and what it therefore cannot establish, next to the number itself.
Not settled: whether the menu's spatial error is misregistration, antialiasing, or
a misplaced soft element. This does not separate them.
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