Grain
As film speed increases, so does the grain of that
film. The grain of a faster film needs to be physically
larger to provide more light-gathering surface area.
While the advantage is greater sensitivity, the larger
grain is more visible in the final image, particularly
as it is enlarged. Larger grain tends to interfere with
overall sharpness and contrast in an image. Theo-
retically, one should use the slowest speed (lowest
ISO) film that is permissible in a given situation. A
slower film will produce a smoother, more uniform
distribution of detail, resulting in a sharper, higher
contrast image. However, extremely large grain,
such as that found in 1000+ ISO films, can be
used to achieve an intentional effect.
In recent years, manufacturers have worked to
reduce grain by increasing the efficiency of the
light-sensitive portions of the emulsion. The result
is greater sensitivity with relatively smaller grain.
An example of this technology is Kodak TMAX,
which provides a smaller grain size than films of the
same speed.
Developer/film combinations can also be used to
try and reduce the size of the grain in the final
image. Fine-grain developers are manufactured for
this express purpose.
Storage and Handling
Film should be kept in a cool, dry place, out of direct
light, when not in use. Even a short-term exposure
to heat can affect the film adversely. Heat can ‘‘fog’’
the film; add exposure to the film that is non-image
forming. The result can be streaks, total film den-
sity, or partial fog, which can cause resulting images
to look dull and have low contrast. Heat can cause
color films to shift color responses, resulting in
unpredictable color reproduction.
For long-term storage, film should be kept in a
refrigerator or freezer (instant film, such as Polar-
oid, should not be frozen). Before using, film that is
stored in either a refrigerator or freezer should be
allowed to reach room temperature before using.
Failure to do so can result in condensation that can
image on the film, as well as potentially damage the
internal chamber of a camera.
Roll film should always be loaded out of direct
sunlight. Sheet film is loaded into special holders in
complete darkness.
Note the film’s expiration date, usually printed
on the film box. If kept at room temperature, film
quality decreases steadily after this date. If frozen
or refrigerated, a film’s ‘‘life span’’ can be extend-
ed significantly.
X-rays, such as those used in airport security
machines, can potentially affect and fog faster ISO
films. Precautionary measures include specialty lead-
lined film bags and request for hand inspections.How an Image Is Recorded
Structure
Film is constructed of several layers on a polye-
ster or acetate base. The top-most layer is the
scratch-resistant coating. Directly beneath this layer
is the emulsion, which holds all the light-sensitive
and image-forming components of the film sus-
pended in gelatin. Beneath the emulsion is an adhe-
sive layer to provide extra support between the
emulsion and the plastic base. Beneath the base is
another layer of adhesive, which mounts the final
layer, the anti-halation coating. This layer is used to
reduce the amount of potential reflection of light
coming back through the film off of the back of the
camera, resulting in a higher contrast image with
greater detail.Response to Light
Within the film’s emulsion are compounds
responsible for the film’s sensitivity to light. These
compounds, known as silver halide crystals, are
made up of silver and a halogen, such as bromine,
iodine, or chlorine. If this combination resulted in a
perfect structure, the crystal would not be sensitive
to light. Because of flaws and irregularities in the
crystal, free-floating silver ions are also present.
When light strikes the silver crystal, it results in
the excitation of electrons within the matrix, which
in turn attracts these free floating silver ions. The
result is a small clump of silver ions, their size
ultimately determined by the amount of exposure
on the film. The exposure must achieve a minimum
threshold to provide at least four atoms of silver to
this clump to make it developable. At this point, the
film has recorded a latent image, chemical in nature
but not viewable on film.The Formation of an Image
After film has been exposed, the resulting latent
image needs to be developed to be visible. Deve-
lopment accomplishes several goals. The first is am-
plification of the latent image to silver metals to
produce a physical image. The second is to neu-
tralize the film’s light sensitivity so that viewing
light does not destroy the intended image. Finally,
the image needs to be ‘‘fixed’’ making it permanent.
The first step in processing any type of film is
development of the latent image. This is usuallyFILM