etc., reflect light in several areas of the spectrum and may be recorded to
some extent in each light-sensitive layer.
10.
Integral Tripack.
Most color films, whether reversal or negative, are integral tripack films.
The term "integral" is used whenever more than one emulsion is coated on a
single base. An integral tripack consists of a single film base with three
light-sensitive emulsion layers coated on one side, each layer responsive to
a separate region of the spectrum.
The three emulsions are not separable
and must be processed together.
a. Structure. An integral tripack emulsion consists of: (1) a suitable
base; (2) an antihalation coating; (3) three individual light-sensitive
layers; and (4) thin layers of gelatin used to separate the light-sensitive
layers that sometime function as filters.
(1) The complete tripack emulsion is about one-thousandth of an inch
thick. The individual emulsion layers are from one to five, ten-thousandths
of an inch in thickness.
(a) Besides silver halides, the emulsion layer may
contain
sensitizing agents and substances for the formation of dye images.
(b) Between the emulsion layers are interlayers of gelatin.
Sometimes they may serve as color filters for the sensitized emulsions, but
their main purpose is to minimize the effects of one layer on the other.
(2) This combination of emulsion layers and gelatin interlayers plays
an important part in image resolution.
Resolving power is a function of
emulsion thickness and the size of the light-sensitive grains. To produce a
color film with normal speed, the grain size must be fairly large.
The
increase in grain size results in a loss of image resolution.
(3) Because of the tripack construction, light striking the emulsion
must penetrate a considerable distance to reach the lower two layers.
In
traveling this distance, the light scatters and the image becomes diffused.
This light scatter also results in lowered image resolution.
(4) To provide adequate light transmission and to retain the sharpest
possible image in the lower emulsion, the top emulsions are designed to be
as transparent as possible.
These emulsions may also contain light-
absorbing dyes to help minimize light scatter.
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SS0514
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