At 15:27 10/21/02, iwert asked:
Hello, I am in a curious mood again...
>From time to time '4 layer film' appears on the list. What exactly is this,
and anyone who knows how it works. Why and when do you need it? Is any
special development needed, and does it exist as color negative and slides?
It's proprietary to Fuji and includes an additional Cyan layer in the film
emulsion. Fuji claims it aids in color balancing prints from daylight film
shot under other than pure daylight, especially with fluorescents which are
more problematic than incandescents. It apparently works as I've had less
problem with properly balanced prints (from a pro lab) using Fuji color
negative films with this feature than with Kodak's. In their consumer
films it's found in the "Superia" line of color negative, including Reala,
but *not* the NHG II color negative or the Sensia E-6 films. In their
professional line it's found in all their color negative films, but *not*
in their E-6 films. All Fuji's color negative films are C-41 process, same
as all other daylight color negative films in current production.
Pull up a data sheet for one of their pro films, or one of their consumer
Superia films (they're PDF files found under Service and Support):
Ex: http://www.fujifilm.com/JSP/fuji/epartners/bin/AF3-007E.pdf
Scroll down the PDF data sheet until you get to the film/emulsion
structure. Typical C-41 films have three layers sensitive to a portion of
visible light:
(1) blue sensitive (creates a yellow image in the negative)
(2) green sensitive (creates a magenta image in the negative
plus has yellow couplers), and
(3) red sensitive (creates a cyan image in the negative).
On raw film there is also a protective layer on top of it all and an
interlayer under each of the three color sensitive ones (the one under the
blue layer has a yellow filter in it). Finally, there's an opaque
anti-halation layer between the rest of the emulsion and the film
base. The opaque substance in the anti-halation layer is washed out during
developing.
The middle (green sensitive) layer in Fuji's color negative films with "4th
layer technology" is slightly different. It's split into two sub-layers
without any interlayer between them. The top two-thirds is similar to all
other color negative, but the bottom third is cyan sensitive producing a
light magenta image when developed. This means it's also sensitive to
longer wavelength blue in addition to shorter wavelength green, spanning
the upper green and lower blue portion of the spectrum. If you scroll down
further and look at spectral response curve, you will see this fourth layer
represented as a dashed line.
Again, this "4th layer" (actually a sub-layer to the middle one) is only
found in Fuji's consumer Superia and all their professional color negative
films. It's not in *any* of their E-6 films, consumer or professional.
-- John
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