1 The Director of Photography – an overview

70 Practical Cinematography
Figure 6.10 A section
through an integral tripack
colour film
WHITE LIGHT
BLUE GREEN RED
Blue ONLY sensitive layer
Green & Blue sensitive layer
Red & Blue sensitive layer
Film Base
If an exposed film of this type is simply immersed in the standard
black and white developer/fixer process, all you will get is three black
and white images. Therefore, a clever bit of chemistry is incorporated
in each of the three emulsions. The chemicals used are known as
colour couplers. Each individual layer has embedded in it a different
colour coupler whose job is, at a molecular level, to form a dye of
the colour complementary to the colour of the light that exposed the
layer. What is more, this dye is formed only where silver is formed by
the developer.
As this is a negative film intended for printing, each layer of emulsion
must end up dyed the complementary colour to the original
scene. Therefore:
● The blue-sensitive layer forms yellow dye.
● The green-sensitive layer forms magenta dye.
● The red-sensitive layer forms cyan dye.
Supercoat
Yellow filter transmits
Green and Red
Interlayer
Antihilation Backing
Early colour film was capable of recording roughly seven stops of
tonal range or a brightness range of 128:1. Modern film stocks have
now been introduced with a tonal range of around 10 stops or a brightness
range of over 1000:1.
This has been made possible by the development of super-thin emulsion
layers and the concept of coating two or three emulsions to make
up each colour layer. Figure 6.11 shows the basic layout of such a film.
The trick is to coat layers of emulsion with different sensitivities, e.g. a
highly sensitive emulsion, a medium sensitivity emulsion and a slow
emulsion, together as a triple layer for each colour. By carefully overlapping
the tonal range of each individual emulsion, the film can