Infrared films, usually created with the incorpo-
ration of dyes, are able to record wavelengths far
outside the visible spectrum. The resulting image is
capable of showing details invisible to the human eye.
CHRISTYESISSONFurther Reading
Adams, Ansel.The Negative (Book 2). Boston: Little Brown
& Co., 1995.
American Museum of Photography.Resources: A Primer
on Process.http://www.photographymuseum.com/primer.html
(accessed May 8, 2005).
Encyclopedia Britannica Intermediate.Photography.http://
search.ebi.eb.com/ebi/article/0,6101,36467,00.html
(accessed May 8, 2005).
Greenspun, Phillip, for Photo.Net.History of Photography
Timeline. http://www.photo.net/history/timeline(accessed
May 8, 2005).
Langford, Michael.Basic Photography. New York: Focal
Press, 2000.
Leggat, Robert, Ph.D.A History of Photography: From its
Beginnings until the 1920s. http://www.rleggat.com/
photohistory/index.html(accessed May 8, 2005).
London, Barbara and John Upton.Photography. 6th ed.
Longman Addison-Wesley, 1998.
PBS Online: The American Experience.Wizards of Photogra-
phy. Eastman Kodak Introduces Full Color Photography.
http://www.pbs.org/wgbh/amex/eastman/peopleevents/
pande19.html(accessed May 8, 2005).
Schaefer, John.An Ansel Adams Guide: Basic Techniques of
Photography, Book 1. Boston: Little Brown & Co., 1992.
Stroebel, Leslie.Basic Photographic Materials and Pro-
cesses. New York: Focal Press, 2000.FILM: HIGH-CONTRAST
High contrast films are marketed for various spe-
cialized application. Depending on the particular
nature of the process, there are different require-
ments for the film in terms of contrast, maximum
density, speed, spectral sensitivity, processing che-
micals, and dimensional stability with their own
specified processing chemistries. Because of strin-
gent technical requirements for each application,
there are subdivided categories of films. This article
will describe high contrast films and their proces-
sing in general terms.
Line photography and halftone photography are
two major parts of graphic arts process photogra-
phy. Reproduction of line drawings begins with
originals in solid black-and-white with no inter-
mediate gray tones. Line films have high maximum
density and high contrast (gradient of 5 to 10).
However, line films must be dimensionally very
stable, of high resolution and provide high fidelity
of reproduction.
Several other high contrast films are often simi-
lar in photographic characteristics to line films.
These include document films, copy films, photo-
typesetting films, and image-setting films. Different
applications have their own requirements in terms
of film size, base material, packaging, and life
expectancy.
Halftone photography is used to convert contin-
uous tone originals (e.g., pictorial photographs) to
halftone images, an optical illusion in which the
tones are represented by solid dots of equal spacing
and density but varying area. Very high contrast
lith films are employed, and films are exposed
twice, one with overall flashing, and another image-
wise, detail exposure. Originals are photographed
onto lith films with a contact screen, a crossline
screen, or other means of screening, and processed
in a special lith developer, which gives rise to lith
effect and extremely high gradient (greater than 10)
to render solid dots of sharp edges.
Line films and lith films differ in terms of devel-
oper solutions in which they are processed. Line
films as well as other non-lith films are typically
processed in rapid access developers that produce aFILM