relative to the needed sharpness of a subject and the
image composition in advance of shooting the pic-
ture, while hyperfocal focusing sets the focus of the
lens on the hyperfocal distance (the minimum focal
distance that will allow infinity to remain sharp in the
image.) Selective focusing and manipulating depth of
field is used in all photographic imagery to direct the
impact of an image’s visual composition and theme.
Limiting depth of field to a shallow area will isolate a
subject from a background, and using a wide depth
of field will emphasize the entire image area. Photo-
journalists and landscape photographers generally
exercise extreme control over depth of field in their
genres. Digital darkroom tools such as Adobe Photo-
shop can also alter the appearance of sharpness in an
image through manipulation tools that increase or
decrease image sharpness in selective areas.
JenniferHeadleySeealso:Camera: An Overview; Enlarger; LensFurther Reading
Adams, Ansel.The Camera. New York: Little, Brown, and
Company, 1991.
Horenstein, Henry.Black and White Photography: A Basic
Manual. New York: Little, Brown, and Company, 1983.
Folts, James A., Ronald P. Lovell, and Fred C. Zwahlen, Jr.
Handbook of Photography. Albany, NY: Delmar Thomp-
son Learning, 2002.
Horenstein, Henry and Russell Hart.Photography. Upper
Saddle River, NJ: Prentice Hall, 2001.
London, Barbara, John Upton, Ken Kobre ́, and Betsy Brill.
Photography. Upper Saddle River, NJ: Prentice Hall, 2002.
Warren, Bruce.Photography. Albany, NY: Delmar Thomp-
son Learning, 2002.
Wildi, Ernest.Photographic Lenses. Amherst, MA: Amherst
Media, 2001.DEVELOPING PROCESSES
Overview
In order to make visible, stable images, exposed
silver-gelatin plates, films, and papers must be pro-
cessed through the use of various chemical solutions.
Most consumer grade prints and fine art prints are
made by the negative–positive system; a negative
film or plate is exposed in a camera and processed
to yield a negative image. This negative image is
exposed onto printing paper by contact printing
(1:1 size) or projection (enlargement). The exposed
paper is processed in a procedure analogous to the
film processing but typically with a separate set of
chemicals. This printing process reverses the tonal
scale again to yield a final positive image.
Processing of black-and-white negative plates,
films, and printing papers is generally a sequence of
five steps consisting of (1) develop, (2) stop, (3) fix,
(4) wash, and (5) dry, but a number of auxiliary
treatments may be added. The development step is
where a visible image is developed from the invisible
latent image contained in films and papers. Stop
bath is used to arrest the development process as
well as minimize the developer carryover to the next
step. The fixing process removes unexposed and
undeveloped parts of photosensitive silver halide
from the negative and papers, thereby making the
material insensitive to further light exposure. The
fixed material is washed to remove the processing
chemicals, and then dried for storage.
In silver-gelatin processes, when an individual
silver halide crystal (0.1 to 3m m diameter in size)
in the sensitized layer of the photographic material
(film or paper) is exposed to light, a tiny speck of
metallic silver (photolytic silver) is created, called a
latent image center. This speck can be as small as a
few silver atoms and is not visible. The latent image
is made visible or developed in the development
step. Individual developed silver grains contain up
to several billion silver atoms. Thus, development
is a chemical amplification process with a gain
factor on the order of a few billion.
On the other hand, there is a class of silver-
gelatin material where development is not used.
This is the printing out process (POP, which also
stands for print out paper), which is extremely slow
contact printing material, mainly used in the early
years of silver gelatin photography. In POP, the
visible image is formed entirely by photolytic silver,
and therefore the exposure must be much moreDEPTH OF FIELD