Glossary
Calotype
Photography's first successful negative/positive process, allowing many positive prints to be produced from a single negative.
First, high-quality writing paper, made light-sensitive with potassium iodide and silver nitrate solutions, was exposed through an
aperture in a camera to light reflected off the desired subject. The latent image became visible when it was developed in gallic acid
and silver nitrate. It was then fixed with hyposulfite of soda and rinsed. The resulting paper negative, or calotype, was placed in
a hinged, wooden frame and contact-printed in daylight on another piece of light-sensitive paper. When the print had developed out
to the desired tonality, the process was chemically stopped and fixed.
The calotype process was patented in 1841 by British photographer William Henry Fox Talbot (1800-1877). The term comes
from the Greek kalos (beautiful). Usually reddish-brown or purplish in color, photographs from calotype negatives are characterized
by broad effects of light and shadow because the texture of the paper prevents sharp details. Waxing the paper negative, a
further refinement, yielded results much closer to the
wet collodion process. The average exposure time was a few minutes or
longer, varying according to the lighting conditions and size of the picture, which could range from tiny to mammoth proportions.
Camera movement
The intentional movement of the camera to create blurred, distorted, faint, or residual effects. Scanning, rotating, or moving
the camera in different directions while photographing a still or moving subject changes the visual effect.
Camera obscura
A portable box with an aperture, lens, and viewing screen. Light enters the box only through an aperture or tiny hole in one wall.
A lens in this opening helps focus the light coming in from the outside. A small, upside-down, and reversed image of a view
outside the box is projected on the opposite wall from the pinpoint light source. By placing a small mirror at a 45° angle on this wall,
the reflected image can be projected on a ground-glass drawing surface on the top of the box. Tracing this projection on drafting
paper yields an accurate rendering of the view.
The term camera obscura comes from the Italian (dark chamber). This forerunner of the photographic camera was created in
the seventeenth century as a drawing aid, although the principle behind the device has been known since the seventh century.
Carbon print
A complex nonsilver positive print with increased permanence and a delicate tonal range. To produce this kind of print a
"carbon tissue" (a thin sheet of gelatin tinted with lampblack) was light-sensitized with potassium bichromate, which hardens according
to the amount of light it receives. The tissue was then exposed to daylight through a negative, pressed into contact with a sheet
of paper, and immersed in a tray of warm water. The water melted away any areas of unhardened gelatin, leaving an image of
varying thicknessand thus varying darknessof carbon pigment in hardened gelatin on paper. A slight relief surface is evident in
the darkest areas where the most pigmented gelatin remains. For even greater richness, these prints were often toned, producing
dense glossy areas in either black or warm brown. The carbon print process was devised in France by Alphonse Louis Portevin
(1819-1882) in 1855 and perfected by Sir Joseph Wilson Swan (1828-1914) in 1864.
Carte-de-visite
A formal calling card popular in the 1850s and patented in 1854 by Andre Adolphe-Eugène Disdéri (1819-1889). These 4½ x
2½-inch (11.4 x 6.4 cm) cards of stiff paper stock had a photograph of nearly the same size attached, usually
albumen prints from wet collodion
negatives. Millions of cartes-de-visite were distributed worldwide in the 1860s and collected in albums by
enthusiasts. Subjects were usually portraits and sometimes landscapes, views of local attractions, or reproductions of works of art. The verso
of the card was printed with the photographer's name and address.
Chloro-bromide print
See gelatin silver print.
Chromogenic process color print
A color print made from a color transparency or a color negative.
Chroma is Greek (color forming). Invented by
Leopolde Mannes (1899-1964) and Leopolde Godowsky (b. 1900) in 1935, the process was acquired and perfected by Kodak.
First marketed under the name kodachrome, chromogenic prints are composed of light-sensitized dyes (dye couplers)
assimilated in at least three layers of gelatin silver emulsion. Each of the three principal layers is sensitized to one of the primary
colors of light (red, green, or blue), with a corresponding dye and developing agent sandwiched in between. The dyes within
the layers act together to produce a color print. At the time of exposure through a negative, a gelatin silver image is formed
in each layer. That colorless image unites the dye couplers with chemicals in the emulsion layers to form the appropriate
combination of colors of the object photographed. Any remaining silver is bleached out of the image and dissolved during
the fixing process. When the emulsion is seen against white background paper, the layers appear as a single, full-color
image. Chromogenic prints, while not as stable as prints from other color process, tend to have the most naturalistic color.
Agfacolor, a commercial transparency film, was first available in 1938. As in Kodachrome film, the Afgacolor dye
couplers are included in the layers of a single piece of film. Kodak
ektacolor, often referred to as "Type C," is the most common
type of commercial chromogenic process color negative film. Introduced in 1942, this dye coupler print process also uses
three separate layers of superimposed light-sensitive emulsion. The layers are protected from other colors of light by
internal filters. During development, both the silver and dye images are made initially. An acid then removes the silver, and the
image is formed on white paper with primary color dyes of cyan, magenta, and yellow.
Cibachrome
See silver dye bleach process print.
Collage/photomontage
In these techniques, fragments from similar or diverse materials are grouped on a common support. In collage, from
the French word coller (to glue), the artistic result relies on the juxtaposition of seemingly unrelated objects and textures.
Usually, no attempt is made to conceal the edges of neighboring and overlapping materials, and handwork in other media such
as painting or drawing may be added as well. Characteristically, the primary concern of collage is an obvious emphasis
on method and visual evidence of the hand of the artist at work.
Photomontage, which incorporates the French
monter (to mount), is an arrangement of photographic material combined
to create a new work. Usually edges are more carefully concealed, and the work may even be made with multiple exposures
in the darkroom or rephotographed to create a more seamless effect.
Collotype
An ink reproduction of a photograph created photomechanically from a prepared printing plate. The technique encompasses
a group of related photographic processes in which the surface of the metal or glass plate is coated first with a base layer
of gelatin with sodium silicate and then with a layer of potassium or ammonium bichromate. The layers are dried by heat.
A negative is contact-printed on the layers of emulsion. The amount of light striking an area determines the hardness of
the second layer of emulsion, and thus some sections are harder than others. The plate is then rinsed, which causes the surface
to swell and buckle, producing a pattern called reticulation. The reticulated surface is very fine, visible only under high
magnification. The textured surface is inked and printed on paper, as in a lithographic process, to create a delicately detailed
image very much like a photograph.
Composite photograph
A work in which multiple images, carefully aligned and registered, are printed on the same sheet of sensitized paper,
using multiple exposures to create a single image. This format was first made popular by nineteenth-century English photographers.
Contact print
A positive made by exposure to an intense light source with a negative laid directly on top of light-sensitive paper, hence
the word "contact." Contact exposures are necessary for photographic papers that need exposure to sun or ultraviolet light.
Salt, albumen, gum, and platinum prints, among others, require contact exposure. Most modern photographs are enlarged,
not contact-printed because the negatives are small. Large-format negatives (4 x 5, 8 x 10, and larger) are often
contact-printed. Contact-printing waned when enlargers became available in the 1880s and when emulsions containing silver bromide
were developed. Using sunlight was no longer necessary because these new emulsions were sensitive to artificial light
sources such as gas or, later, electric light.
Cyanotype
A print created by the light sensitivity of iron salts. The process, invented by Sir John
Herschel (1792-1871) in 1842, creates economical and permanent prints in insoluble Prussian blue paper. A piece of good drawing paper is brushed with
solutions of ferric ammonium citrate and potassium ferricyanide and then dried in the dark. The object to be reproduced was placed
on top of the prepared paper in direct sunlight for about fifteen minutes or until the image formed. The paper darkens
when exposed to light, creating a white image on a blue ground. The paper is then washed and fixed in a bath of water.
The cyanotype is a convenient process for reproducing architectural drawings, hence the present-day name, "blueprint."
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