The landing card sells "35mm & 120 Film Grain — authentic grain structures plus
halation bloom, tuned per stock rather than one global overlay", and the engine
printed one field for everything: a width/1080 cell, one spread, no bleed.
`shared/utils/grainShader.ts` (new, the web fork of the phone's
src/utils/grainShader.ts) now carries the stock table — format, cell, spread,
octave mix, halation, halo radius, halo tint — and `grainStockFor(
recipe.baseFilter)` picks the one this recipe prints.
FORMAT. 35mm cells are the 1.0 reference the knob was tuned at (classic-negative
1.15, B&W high contrast 1.25); the 120 emulsions sit at 0.55-0.72 and open their
base octave (mix 0.55/0.30/0.15 -> 0.62/0.26/0.12), so the same knob prints a
finer, smoother texture on the bigger negative. Measured on a flat 128 grey at a
3200px preview (cells 3.41px vs 1.63px), GRAIN 10, luma residual against a 17px
box:
35mm CLASSIC NEGIPES r1 0.793 keeps 0.976
35mm CLASSIC CHRIPES r1 0.744 keeps 0.931
35mm B&W HIGH CONTRAST r1 0.812 keeps 1.002
120 PROVIPES r1 0.423 keeps 0.728
120 VELVIPES r1 0.313 keeps 0.672
120 ACRIPES r1 0.543 keeps 0.794
r1 is the lag-1 autocorrelation of the residual — how coarse the clumps are —
and "keeps" is the residual sd after a 2x box downscale over the sd before, i.e.
how much of its texture a print at half size holds on to. Every 35mm stock beats
every 120 stock on both, and VELVIPES (0.55 cell) is finer than PROVIPES (0.62)
inside 120, so the format is a look and not a label. Raw sd is NOT the measure:
the knob drives one alpha for every stock, so a stock's amount follows its cell
and mix rather than the order anyone assumed.
HALATION. A new pass 6b thresholds the print (T0 0.62, T1 0.92), tints what is
left the stock's halo colour — red, because red is the light the emulsion passes
and the backing returns — blurs it at the stock's own radius and screens it back
at `halation * grain/10 * 0.6`. Riding the GRAIN knob keeps today's contract:
OFF is still a clean frame, the OFF/WEAK/STRONG chips still mean 0/3/6, and a
sensor stock carries none at any amount. Measured R-B of the ring around a white
block on black, GRAIN 6 minus GRAIN 0 (mean, and the ring's reddest pixel):
CLASSIC NEGIPES 7.87 (peak 0 -> 14) VELVIPES 3.71 (0 -> 13)
CLASSIC CHRIPES 2.91 (0 -> 10) PROVIPES 2.01 (0 -> 7)
B&W HIGH CONTRAST 0.61 (0 -> 5) ACRIPES 0.24 (0 -> 3)
LC STREETLIFE CLASSIC 0.09 (0 -> 0)
which is the table's own halation column (0.45 > 0.30 > 0.25 > 0.18 > 0.15 >
0.12) in order: the colour negative halates hardest, the B&W emulsions barely,
Acros — no colour layer to bleed — least of all, and the sensor not at all. The
colour negative's own grade leaves its ring blue at GRAIN 0 (-5.96 there), so
the statistic is the change and not the absolute channel; in a crop of the block
the bloom itself is unmistakable at GRAIN 6 and 10 and absent at 0.
GRAIN_SEED moves here from exportEngine.ts so the roll is still one per page
load, and still shared by the preview, the compare copy and the file.
Checked: tsc --noEmit clean; grain-stock-test 53 PASS / 0 FAIL; sims-test 31/0,
fx-mono-test 15/0, grain-size-test 12/0, grain-analog-test 7/0, wm-font-test
green.
ponytail: halation rides the GRAIN knob instead of a control of its own, since
the card promises no more than "tuned per stock". Add a HALATION chip when the
phone grows one.
ponytail: `grainCell`'s 1px floor is the aliasing guard, and it also hides the
format ratio under a ~1600px preview. Nothing to add: the exported file is
always wide enough, and the harness renders at 3200 to see it.
