dtourolleandClaude Opus 5
e9b3598841
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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>