At 10:33 10/22/02, Dan Mitchell wondered:
I'm missing something -- how does the extra layer help here? If it's the
same processing as any other film, how can the printing machines(person)
'use' the extra layer to balance the colours? If it was a physically
separate thing that could be removed and used to calibrate, I could see it,
but if it's just another layer of emulsion, surely all that happens is that
the resulting negative is possibly slightly differently coloured to the one
without the extra layer.
[snip]
This remains something of a mystery to me also. I do know that print
machines have "channels" that set up the basic filter pack, with different
channels for different films. There are other calibrations and tweakings
that go from there.
Additional things I know from our color matching folks at work . . .
The human eye is very sensitive to changes in hue around the green portion
of the spectrum. Very, very slight changes in wavelength in this region,
on the order of just a few angstroms, are detectable by most people. Our
color folks shudder when customers want very specific hues of green LED
backlighting for LCD displays. Sometimes this requires a mix of a couple
LED colors to achieve making it more nightmarish. The human eye is not
nearly as sensitive to similar shifts of a few angstroms in other spectral
regions. The spectral sensitivity charts on the 4-layer films show the
cyan as providing some additional sensitivity between the blue and green
curves with a fourth peak there. My best guess is it provides additional
hue gradation in this region and that's just an educated guess. It's
likely only someone from Fuji's engineering staff could provide a complete,
definitive answer.
Is it that the cyan layer 'activates' under flourescent light to help
cancel the colouring effects of the lights out, but doesn't do anything in
daylight? If so, does this mean that if you took photos of a subject that
happened to be "flourescent-coloured", you'd end up with the final image
looking strange because the film couldn't tell the difference?
That I don't know, but cannot imagine that it would. I do know under mixed
lighting with halogen spots, lower wattage incandescents and daylight
(without any fluorescent), Press 1600 did remarkably well (printed by a pro
lab that does excellent color balancing in general). According to the lab,
it's easier for them to balance prints properly when making them from from
"daylight" 4-layer negatives shot under mixed conditions.
-- John
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