1 The Director of Photography – an overview

116 Practical Cinematography
Figure 13.1 How a laboratory
corrects the exposure of an
18 per cent grey card
Controlling print density
A technique very often used, especially when shooting a low-key
scene, is to place all the important tones along the middle, straight-line
section of the sensitometric curve and then have the laboratory print
the scene down to its correct brightness range. The reason for doing
this is to obtain a finer grain structure and dense blacks.
You get the finer grain, which in a low-key scene will show mainly
in the blacks, where the grains are bigger and the exposed grains are
further apart. By bringing the blacks up the curve they will be photographed
on a finer-grained part of the emulsion structure.
The dense blacks come from not using the non-linear bottom end
of the curve but keeping them on the straight-line section, where they
are more easily and reliably controlled using the three-point system
described in the previous chapter. If the laboratory printed this scene
in the middle of the scale the blacks would be dark greys – just as they
were exposed.
By putting a grey card on the front of the scene, overlighting it by,
say, half a stop and then asking the laboratory to print to the grey card,
you will be making the laboratory print all the scene down by half a
stop. If half a stop is the amount the blacks were ‘sat up’ in the first
place, then you will get back a beautifully graded low-key scene with
unusually rich and dense blacks.
Figure 13.1 shows in graphical form how the darker or lighter grey
card is brought back, and with it the following scene, to the correct
print density.
This technique works for a low-key scene. The highlights will have
been slightly crushed if both the negative and the scene have a sevenstop
maximum tonal range, or a lighting ratio of 128:1. This does not
usually matter as, in most low-key scenes, we are rarely interested in
very much information in the highlights.
With the above example you could improve the highlights dramatically.
Instead of using a negative with a finite tonal range of seven
stops, why not select a negative having a longer tonal range? For example,
Kodak have an excellent 320 ASA negative with a tonal range of
over 10 stops; 320 ASA is an ideal speed for both night interiors and
18% Grey
Card
18% Grey
Card
18% Grey
Card
Correctly
Exposed
OVER
Exposed
by HALF
a Stop
UNDER
Exposed
by HALF
a Stop
Laboratory
Grades Card
Correctly
Laboratory
PRINTS
DOWN
Half a Stop
Laboratory
PRINTS
UP
Half a Stop
�
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Correctly
Graded card
on Print
Correctly
Graded card
on Print
Correctly
Graded card
on Print