1 The Director of Photography – an overview

108 Practical Cinematography
Lighting Ratios on Sphere
Highlight : Sphere � 2:1
Sphere : Shadow � 2:1
Shadow : Deep Shadow � 4:1
Highlight
Highlight : Shadow � Highlight : Sphere � Sphere : Shadow � 4:1
Highlight : Deep Shadow �
Highlight : Sphere � Sphere : Shadow � Shadow : Deep Shadow � 16:1
Sphere : Deep Shadow � Sphere : Shadow � Shadow : Deep Shadow � 8:1
Figure 11.2 The relationship
between a highlight, the
mid-tones, a shadow and a
deep shadow
Sphere
(mid-tone)
Shadow
Deep Shadow
black and the whitest white will measure a difference of no more than
seven stops.The black will never read as absolute black, since there will
always be some spurious light, even if it is only that which has arrived as
atmospheric flare, for the highlights in the scene displayed have to travel
through the atmosphere in the cinema. The cinematographer’s lot has
been much improved since smoking was banned in many cinemas.
This means that the maximum lighting ratio that we can display in
the final picture on the screen is 128:1, the equivalent of seven stops of
exposure difference. It is important to realize that any parts of the scene
outside this ratio of 128:1 will have no detail or information in them
whatsoever.They will appear as either solid black or solid white. Keeping
all the important information in a scene within the lighting ratio of the
final delivery system is therefore crucial to the success of the scene.
When shooting for television, matters are more constrained. If you
look at your television screen when it is switched off, it will appear to
be dark grey. This is as dark as it will ever get. When a picture is displayed
on the television screen, parts of that picture only appear
black, or darker than the screen when switched off, because of the way
our eyes and brain expect to perceive the relative brightness between
the highlights and the shadows. A strong highlight anywhere in the
scene will make the blacks appear darker still.
Even the finest television screen can only display a brightness ratio
of 32:1 or the equivalent range of five stops of exposure range. It is
important, therefore, not to light anything in a scene that you feel the
audience should be able to perceive, even if only as a faint texture, outside
a lighting ratio of 32:1. As with the cinema, but now over a much
restricted range, any part of the scene outside this range will appear as
either solid black or solid white. Parts of the scene that are solid black
or white on a television screen are far less pleasant than in the cinema,
because they attract electronic noise and, as this is an unnatural
phenomenon in normal vision, even an untrained viewer’s eye and
brain will instantly know something is wrong. This must therefore be
avoided.