Film
speed is measured by Eastman Kodak in the United States
in graduations called ASA or ISO. Speed refers to the
amount of time needed to burn-in an image. The complete
explanation is not that important at this point. What
concerns a filmmaker is how does ASA affect the performance
of their film. The faster the film, the less light is
required to get a particular shot. For a night shot, fast
film should be used. The trade off is, the higher the
ASA, the grainier the image. Slow film on a sunny day
would be almost devoid of grain. Fast film shot in low
light conditions would appear noticeably more grainy.
Grain is usually distracting and should be avoided unless
you are re-creating newsreel footage or some similar effect.
Beware of creating unnecessary grain when shooting in
16mm, the small image size really makes grain obvious.
Light your scenes carefully avoiding big white areas because
the grain just swims against white walls. In 35mm, the
image area is four times larger and hides goofed-up lighting
much better.
