Film’s Evolution
In 1871, R.L. Maddox, an English photographer,
pioneered the dry plate process. This process made
photography considerably more convenient, as the
photographer was now free to photograph without a
portable darkroom in tow. In addition, emulsions
became more sensitive, allowing exposures in fractions
of a second instead of minutes. The camera was now
truly a portable device, and the snapshot was born.
The final steps in the evolution of film came
with the invention of gelatin in the 1880s, a thin
flexible material in which the emulsion could be
suspended and coated onto virtually any surface.
The ideal surface came a few years later with the
use of a thin, flexible cellulose. By coating gelatin
emulsion onto this new, flexible base, photogra-
phers were no longer restricted to large view cam-
eras or the limitation of only shooting one image,
then needing to reload the film. The new flexible
film could be made into rolls, allowing images to
be photographed quickly and in sequence. George
Eastman of Eastman Kodak was at the forefront
of this photographic revolution, manufacturing
some of the first pre-loaded consumer-based cam-
eras. Once the roll was exposed, the camera was
sent back to the company for processing. Kodak’s
famous slogan, ‘‘You take the picture, we’ll do the
rest,’’ outlined the new convenience roll film
afforded the world of photography.
Modern Film
Modern film comes in many types, depending on
what the photographer wants as a final outcome.
Black and white films result in images made up of
thousands of tones of gray. Color films are
designed to reproduce the most realistic color pos-
sible in a given situation. There are special applica-
tion color films as well, designed to render a pastel
version or even a highly saturated version of the
original scene.
Negative films, available in both color and black
and white, most often are used if a photographic
print is the intended final outcome. Slide film,
(most often color) also called reversal film, pro-
duces positive transparencies of the image. Color
slide film comes in different color balances, day-
light balanced, and tungsten balanced. Each film
most realistically represents color in the scene when
photographed using those light sources.
Other considerations when choosing film include
film size. Roll film, used in most consumer cam-
eras, includes 35 mm, medium format film (120 mm
and 220 mm), APS (Advanced Photo System) and
miniaturized formats, such as disc film and 110-
cartridge film. Sheet film, typically used in view
cameras, is most commonly found as 45-inch
film, but can come in sheets as large as 810-inches.
Films for specialized applications include ins-
tant film, popularized by the Polaroid Company.
This film contains the processing chemistry within
its structure, allowing the film to be processed
almost immediately after exposure. High contrast
film, sometimes known as graphic arts or litho-
graphic film, produces monochromatic images
using only black and white, with no shades of
gray in between.Film Speed
Film sensitivity, or the amount of light needed to
make a proper exposure, is determined by the film’s
speed. Film speed is denoted by its ISO (Interna-
tional Standards Organization), which is based on
testing done by the manufacturer. ASA (American
Standards Association) is an older notation that
uses the same numerical system of determining a
film’s speed.
The film speed determines how sensitive that film
is to light. The more sensitive the film is to light, the
higher the film speed, and the ‘‘faster’’ the film. The
less sensitive the film is (the more light it needs), the
lower the film speed number; lower numbers are
considered ‘‘slower’’ films. For example, a film
with an (ISO) speed of 400 is very sensitive to light
and is considered to be fast. Part of the reason for
this terminology relates to how these films are used.
Since an ISO 400 film needs very little light to make
an exposure, this allows the photographer to shoot
in low-light situations. It also allows for the freezing
of motion, since the film allows for smaller and
smaller fractions of seconds to be used. In contrast,
a slower film, such as ISO 100, needs a greater
amount of light to make a proper exposure.
ISO numbers correspond directly to the sensitiv-
ity of the film.
Film Speed Amount of light needed
ISO 100 ****
ISO 200 **
ISO 400 *
ISO 100 film needs twice the amount of light to
make an exposure as ISO 200 film, which needs
twice as much as ISO 400 film. Respectively, ISO
400 speed film requires half the amount of light to
make an exposure as ISO 200. For every doubling
of ISO numbers, the amount of light needed is cut
in half.FILM