FILM: INFRARED
In a rainbow we see the decomposition of sunlight
in its visible components, however, there are parts
of this light not detectable by human vision. Be-
yond violet rays are ultraviolet rays to which pho-
tographic film is also sensitive, below red rays there
are infrared rays. Photographic films thus make it
possible to ‘‘see’’ more of the electromagnetic spec-
trum, and infrared film makes it possible to photo-
graph within wavelengths between 730 and 900
nanometers (nm—one-millionth of a millimeter).
This film is used for various scientific applications
as well as by fine arts photographers for its aesthe-
tic appeal.
For the purposes of photography, the wave-
lengths of 730 to 900 nm are called the near infra-
red, and cannot normally be perceived in any way.
Far infrared, which can be felt as heat, is 900 nm
and beyond, some people define the end of this
spectrum at 1200, others at 1400. ‘‘Normal’’ film is
aimed towards reproducing, as close as possible, the
spectrum of human vision, with the exception of
early photographic emulsions, which were sensitive
only to the ultraviolet and blue parts of the spec-
trum. Light sources other than the sun produce
different spectrums. Tungsten light has a spectrum
leaning more in the yellow and red part of the
spectrum, and is high on infrared radiation. Dis-
continuous light sources, such as fluorescent, neon,
and sodium vapor lamps produce little or no infra-
red light.
Infrared film was designed to photograph in the
near infrared part of the spectrum; the expected
uses were scientific and military. With this film it
is possible to photograph scenes illuminated by
infrared rays that would not be visible by the sub-
ject. Differences invisible to ‘‘the naked eye,’’ could
be captured by infrared film ‘‘illuminated’’ with
infrared radiation. Although designed to photo-
graph in the infrared part of the spectrum, most
infrared films are also sensitive to visible light.
Each of the commercially manufactured black
and white infrared films, however, has its own
particular characteristics: Kodak Infrared High
Speed film (Kodak HIE) is the more widely avail-
able; it also has the highest sensitivity in the infra-
red part of the spectrum. It produces the soft and
grainy images characteristic of pictorial infrared
photography, is available in 35 mm and wider
rolls for use in aerial photography. Sheet film for-
mats are only available by special order. The
Konica Infrared 750 has a name describing its
sensitivity peak at 750 nm; its sensitivity falls
sharply beyond that point. In the visible part of
the spectrum it is sensitive to blue light. It is slower
in speed, with higher contrast and finer grain than
Kodak. It is available in 35 mm and in 120 formats.
Ilford SFX 200 addresses itself to the pictorial uses
of infrared. Its infrared sensitivity is not too wide
and is promoted as a ‘‘special effects’’ film, not as
an infrared one. The newest comer is Maco 820; the
number 820 describes its sensitivity limit. Users
report it to have characteristics close to the Konica
Film; produced by a small German company it is
not widely available.
The only available color slide infrared film is
Ektachrome Professional Infrared, and it is sensitive
to infrared in the 700 to 900 nm region, providing
false colors, with infrared reflecting objects appear-
ing with red or magenta tones. Like infrared black
and white film, it requires filtering for best results.
All these films require special care while loading
and unloading the camera. The Kodak films even
require all handling operations to be made in com-
plete darkness. Other special care should be taken
when using infrared films: Some modern cameras
have infrared devices for loading and frame count-
ing; these devices will, in most cameras, fog a part of
the film frame. Infrared light may focus at a differ-
ent point than visible light, thus some lenses are
marked with an infrared focusing mark, while
some Konica Hexar models had their autofocus
systems with two infrared focusing programs. For
Kodak and Konica films, however, the easiest way
of dealing with infrared focus shift is to use a wide
angle lens with a small lens aperture to get more
depth of field. Another difficulty related to the use
of infrared film is the fact that exposure meters are
not reliable on setting infrared exposure. Testing is
the only way to set infrared exposures, and the best
starting point is on film manufacturer’s tables.
As infrared films are also sensitive to visible
parts of the spectrum they are used with filters toFILM: INFRARED