3dtours
d1e9425b9c
sensorWhite hung its nine counts of window off the plane's largest sample. A hot pixel sits hundreds of counts above the level the sensor stops at, so on a frame that carries one the window held the stray alone, found no pile in it, and handed the develop the factor two instead of the frame's own level. Measured on a Panasonic DMC-LX10 RW2: one sample at 15993 and one at 14665 over a pile of 9,594,544 at 13855. The frame's level is 1.75x the fall-back, so the develop opened 0.81 of a stop bright, clipped the sky the sensor had held to flat, and the fit to the camera's preview could only pull the exposure back after the highlight detail was gone. Against the camera's own JPEG of the shot, mean |dL| 23.48 and dRGB +8.57,+0.90,+4.90 became 19.14 and +5.32,+1.89,+2.04, and the level itself 7908 (gain 8.2872) became 13874 (gain 4.7236) against the 13855 the plane piled at — 0.14%, 0.002 of a stop. The level is now the highest count the plane piled at, off a whole-plane histogram: `floor` counts is a pile, and the same cliff rule as before still has to hold over the count below it, so a smooth bright sky is left alone and a frame that has not clipped still falls back on the factor two. The same stray was in four of the ten bodies to hand. A Nikon _GDN0447.NEF read the fall-back 8190 where its plane piles at 13806 (gain 8.0018 -> 4.6022, 0.79 of a stop), a Fujifilm RAF 29696 where the documented level is 30993, and a Sony ARW 31742 against the 2.002x the body's ratio was measured at. Six were untouched, and a Canon CR2 develops byte-identical through the change — the window moves only on a frame whose largest sample is not its highest pile. scripts/white-level-check.mjs keeps the LX10 shape: a plane piled at 30995 with a stray above it has to answer 30995.
81 lines
4.2 KiB
JavaScript
81 lines
4.2 KiB
JavaScript
// Where the develop's white level comes from (src/engine/sensorWhite.ts). The
|
|
// probe reads the frame instead of trusting a constant: the plane's ceiling is
|
|
// 1.89-2.00x `maximum - black` and which one depends on the body, and a frame
|
|
// that sat below the desaturation's 0.95 start came out tinted (Fuji X-Trans,
|
|
// measured 1.892). These pin the two states it has to tell apart — a blown
|
|
// plateau (spike plus gap) and a bright smooth sky (a top bin no bigger than the
|
|
// ones under it) — and the fall-backs on frames with nothing to measure.
|
|
//
|
|
// node scripts/white-level-check.mjs
|
|
import assert from 'node:assert/strict';
|
|
import { readFileSync } from 'node:fs';
|
|
import ts from 'typescript';
|
|
|
|
const src = readFileSync(new URL('../src/engine/sensorWhite.ts', import.meta.url), 'utf8');
|
|
const js = ts.transpileModule(src, {
|
|
compilerOptions: { module: ts.ModuleKind.ESNext, target: ts.ScriptTarget.ES2022 },
|
|
}).outputText;
|
|
const { sensorWhite } = await import(`data:text/javascript,${encodeURIComponent(js)}`);
|
|
|
|
const N = 1_000_000;
|
|
const MAXIMUM = 16383;
|
|
const BLACK = 512;
|
|
const LEGACY = 2 * (MAXIMUM - BLACK);
|
|
const FLOOR = 8192; // an unremarkable mid-tone the frame is mostly made of
|
|
|
|
// A frame of `N` mid-tone samples plus `counts` of them sitting in the nine bins
|
|
// from top-8 up to top: counts[8] is the top bin, counts[0] the one eight below.
|
|
function plane(top, counts) {
|
|
const data = new Uint16Array(N);
|
|
data.fill(FLOOR);
|
|
let i = 0;
|
|
for (let d = 0; d < 9; d++) for (let k = 0; k < counts[d]; k++) data[i++] = top - 8 + d;
|
|
return data;
|
|
}
|
|
|
|
// The sensor's own plateau: a pile at the top with nine near-empty bins under it.
|
|
assert.equal(sensorWhite(plane(30995, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), 30995, 'X-Trans plateau missed');
|
|
assert.equal(sensorWhite(plane(31779, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), 31779, 'Sony plateau missed');
|
|
// ...and the body that really does sit at twice the white level is read as such,
|
|
// not as the constant it used to be. Same answer either way, which is the point:
|
|
// the probe does not need to know which body it has.
|
|
assert.equal(sensorWhite(plane(LEGACY, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), LEGACY);
|
|
|
|
// A smooth sky fills the bins around the top far more than a clipped one does,
|
|
// and its top bin is a tail, not a step: no gap, no clip, no move of the white.
|
|
assert.equal(
|
|
sensorWhite(plane(30995, [400, 900, 1500, 2000, 2400, 2600, 2600, 2400, 2000]), MAXIMUM, BLACK),
|
|
LEGACY,
|
|
'a smooth top read as a clip'
|
|
);
|
|
// A bright flat wall sits exactly on one value with a big pile — but the bins
|
|
// under it are empty too, so that one IS a clip and is meant to move the white.
|
|
assert.equal(sensorWhite(plane(30995, [0, 0, 0, 0, 0, 0, 0, 0, 5000]), MAXIMUM, BLACK), 30995);
|
|
|
|
// Nothing to measure: a frame that never reached the plane's ceiling, and one
|
|
// whose only pile is a handful of hot pixels, both stay on the fixed factor two.
|
|
assert.equal(sensorWhite(plane(9000, [1, 1, 1, 1, 1, 1, 1, 1, 3000]), MAXIMUM, BLACK), LEGACY, 'an unblown frame moved the white');
|
|
assert.equal(sensorWhite(plane(30995, [0, 0, 0, 0, 0, 0, 0, 0, 5]), MAXIMUM, BLACK), LEGACY, 'hot pixels moved the white');
|
|
|
|
// A hot pixel above the plateau is not the ceiling: the window is hung off the
|
|
// pile, not off the frame's largest sample. Measured on a Panasonic DMC-LX10 RW2
|
|
// — a pile of 3.1M at 13855 with one sample at 15993 over it — reading the stray
|
|
// as the top left the nine bins under it empty, the frame fell back on the factor
|
|
// two (7908 against its own 13855) and opened 0.8 of a stop bright with its
|
|
// highlights clipped flat.
|
|
const strayed = new Uint16Array(N);
|
|
strayed.fill(FLOOR);
|
|
for (let i = 0; i < 400_000; i++) strayed[i] = 30995;
|
|
strayed[600_000] = 34000;
|
|
strayed[700_000] = 32400;
|
|
assert.equal(sensorWhite(strayed, MAXIMUM, BLACK), 30995, 'a stray sample above the plateau moved the white');
|
|
|
|
// The pile is a fraction of the plane, not a fixed count, so a small sensor with
|
|
// the same clipping is read the same way as a large one.
|
|
const small = new Uint16Array(100_000);
|
|
small.fill(FLOOR);
|
|
for (let i = 0; i < 40; i++) small[i] = 30995;
|
|
assert.equal(sensorWhite(small, MAXIMUM, BLACK), 30995, 'a small plane moved the threshold');
|
|
|
|
console.log('white-level-check ok');
|