2 Commits

Include renames

Author	SHA1	Message	Date
dtourolleandClaude Opus 5	e9b3598841	Add five Ilford stocks, and say plainly that they are constructed ... They were asked for and they are here, but not on the same footing as the Kodak profiles, and the files say so in their first line. What I had claimed, and had to withdraw: that Delta 100 is "quoted around 9" and HP5 "around 12". Ilford publish no such figures. The word granularity does not occur anywhere in their technical information -- grain is described as "fine" and "finest" and nothing more. That claim was in this crate's documentation as though it came from a datasheet; it is corrected there too. Two further traps found while looking: - Kodak colour negatives publish Print Grain Index, not RMS granularity. PGI is a perceptual scale from viewer surveys -- 25 is roughly the threshold of visibility, four units a just-noticeable difference -- and Kodak state it cannot be compared to RMS. So a Portra number cannot be dropped into the granularity field, and none has been. - RMS proper is published mostly for black-and-white, reversal and motion picture stocks. Every shipped stock therefore still carries the same default, which means grain does not yet tell one film from another. That is per-stock data, not code, and is now written down where somebody will find it. So the Ilford profiles are built rather than extracted, and each part rests on something different: speed published and exact -- ISO 400/27 for HP5 is a fact contrast ISO 6:1993's normal development, average gradient 0.62 spectral borrowed from Kodak Double-X, a *measured* panchromatic negative, shifted by the speed difference. Conventional panchromatic sensitisation is much alike across black-and-white films, and this is far better founded than reading pixels off a printed curve silver neutral, which is not an approximation: developed silver absorbs flat, and Double-X's measurement is flat granularity estimated, ordered by each film's known relative grain They render as a film of that speed and contrast. They are not a measurement of that emulsion, and the two stocks that share a speed differ only in the estimated part. `every_shipped_stock_bakes` is tightened to match, because a constructed profile fails in a way a measured one does not: the curve parses, bakes, and sits entirely off one end of its own exposure range, rendering every frame black or blown while passing a finiteness check. It now asserts mid-grey lands somewhere photographic and that the tone response runs the way the stock's kind says it should. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-08-26 10:08:51 +02:00
dtourolleandClaude Opus 5	4b2ee0ac50	Count the silver instead of adding noise ... An emulsion is a suspension of crystals. Light sensitises some; development turns a sensitised one opaque, all or nothing. So a patch of film's density is a *count* of developed grains, and a count of independent yes/no events has a variance whether or not anyone wanted texture: mean = D variance = D * (Dmax - u * D) / N That expression is the whole feature. It peaks in the middle of the density range and vanishes at both ends -- clear film has nothing developed to vary, black film has nothing left to develop -- so grain lives in the midtones as a consequence rather than as a "midtone bias" slider. I was wrong earlier that this needs the detail stage. Nothing in it reads a neighbouring pixel; the only reason to move it was that grain must be fixed in film space rather than screen space, and that solves itself: N is grains *per pixel*, so it scales with the film a pixel covers. Zoom out, each pixel averages more grains, less variance -- correct, with nothing super-sampled and nothing filtered. It stays in the fused pass. Grain goes on the density and *before* the dye, which is the physical order and not cosmetic. Perturbing the finished colour -- what an effect does -- tints highlights wrong, because that noise never passes through the dye. Crystal habit lives in `rms_granularity`, the number every datasheet publishes, now a profile field. It measures exactly what differs between a cubic emulsion and a tabular one: at equal speed, tabular crystals present more area per unit silver, so the film reads finer. Delta 100 is quoted near 9 where HP5 is near 12, and that gap *is* the habit. Adding a stock whose grain is its whole reputation is therefore editing one line, not writing a model. Three things this cost, all of them worth writing down: - The default granularity is a colour negative's, blue coarsest. Applied to Tri-X it put *colour* speckle on a black and white photograph. Monochrome stocks collapse it at parse, where every other per-layer table is already replicated from the one measured channel. - Helpers cannot read uniforms. The composer prefixes a uniform with its operation's id and rewrites references inside a fragment body only; helpers are shared and deduplicated, so a bare `gn0` names nothing. `film_lut` already took its size as an argument for this reason, and now says so. - The end-to-end test compares the shader against the CPU model, and grain is stochastic, so that comparison now runs with grain off. Which means a grain that never left the CPU would look exactly like a passing suite -- hence a second test that grain off is bit-identical, one grain per pixel moves it, and ten thousand move it less. Not here, deliberately: no grain slider. The parameters are physical and `rms_granularity` is the honest place to scale one from, but its range wants choosing rather than guessing. Nor a film format -- 35 mm is assumed, and medium format at the same stock is far less grainy per unit of picture. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-08-26 10:08:51 +02:00