Additive color: See Color, additive

Albumen print: Albumen prints are the most common type of photographs from the 19th century and were the first photographic prints in which the image was suspended on the surface of the paper instead of being embedded in the fibers of the paper. The process involves coating a sheet of paper with albumen (egg white), which gives the paper a glossy, smooth surface. The albumenized paper is sensitized with a solution of silver nitrate, then exposed in contact with a negative, generally a collodion on glass negative. Albumen prints are "printed-out," meaning that the image is created solely by the action of light on the sensitized paper without any chemical development. The printing-out process requires long exposures and results in prints that are susceptible to fading. Despite these problems, the ability to capture fine detail and the relative ease of producing many prints from a single negative helped hasten the replacement of direct-positive processes, such as daguerreotypes and ambrotypes, by negative-positive processes. Albumen prints, which were invented in 1850 by Louis-Desiré Blanquart-Evrard, replaced salted paper prints as the dominant type of photograph; they were, in turn, replaced by gelatin silver prints in the 1890s.

Ambrotype: Ambrotypes are sharply detailed, one-of-a-kind photographs on glass, packaged in protective cases similar to those used for daguerreotypes. An ambrotype is essentially a collodion on glass negative that is intentionally underexposed so that the negative image appears as a positive image when viewed against a dark background. The process for making ambrotypes was patented in the United States in 1854 by James Ambrose Cutting. Ambrotypes (and the closely related tintypes) soon replaced the more expensive daguerreotypes as the favored process for portrait photography. The process has the additional benefit of being non-reflective, making ambrotypes easier to view than daguerreotypes. The popularity of ambrotypes was short-lived, however, and the process was soon displaced by the growing popularity of the negative-positive process of collodion on glass negatives and albumen prints.

Cabinet card: The cabinet card—a popular format for 19th-century photographs—is a photograph mounted on heavy card stock and measures approximately 6-1/2 x 4-1/4 inches. Cabinet cards are usually studio portraits, and cabinet cards of celebrities, a favorite subject, were widely collected in the last quarter of the 19th century. The format was introduced in 1866 and soon surpassed the smaller carte-de-visite format in popularity. Cabinet cards lost much of their popularity after 1900 and largely disappeared by the end of World War I.

Calotype negative: The calotype negative is a paper negative and was the first negative to rely on the chemical development of a latent image on light-sensitive paper that had been exposed in a camera. The process was patented in England in 1841 by William Henry Fox Talbot. It was an advancement on Talbot’s first paper negatives, called photogenic drawings, that were produced solely by the effect of light on light-sensitive paper. The chemical development process meant that calotype negatives required much less exposure time than photogenic drawings. One calotype negative could be used to make many prints (at the time, salted paper prints), and this negative-positive process was the direct antecedent to modern photography. The longer exposure time and the lack of precise image details made calotypes less popular than daguerreotypes for portraiture, but calotype negatives and salted paper prints were popular during the 1840s for many other photographic practices, such as architectural and view photography. Calotype negatives were largely replaced by collodion on glass negatives in the mid-1850s.

Carbon print: A carbon print is a pigment print that relies on the use of a bichromated colloid mixed with a pigment (usually carbon black) for the formation of the print image. Carbon prints are noted for their permanence and their rich and glossy dark tones. To make a carbon print a sheet of paper is coated with bichromated gelatin mixed with carbon black. The paper is exposed in contact with a negative; the gelatin hardens in proportion to the amount of light received. After exposure, the paper is pressed in contact with a second sheet of paper that has been coated with an insoluble gelatin layer. When the two sheets are soaked together in water, the first sheet floats free and the unhardened gelatin washes away, with the carbon image transferred in relief to the second sheet. The carbon print process was patented in France in 1855 by Alphonse Louis Poitevin, and reached the height of its popularity between 1870 and 1910.

Carbro print: A Carbro print is an assembly of three bichromated gelatin tissues, each pigmented with one of the primary subtractive colors, cyan, magenta, or yellow. The image on each tissue is formed as a result of a chemical reaction that occurs when the bichromated gelatin tissue is placed in contact with a silver bromide print. The silver bromide prints, each made from a black-and-white separation nagative (see Color, additive) cause the tissues’ gelatin to harden in proportion to the density of the print. The unhardened gelatin is then washed away. When these tissues are placed in exact register onto a paper support, they combine to produce a full-color (tricolor) photograph. The Carbro process, patented in 1905 as the Ozobrome, was adapted from carbon printing techniques developed in the 1850s. Though monochromatic Carbro prints were made, this process is best known through its vivid three-color images. Carbro prints are also noted for their image permanence.

Chromogenic development process: See Color transparency, chromogenic development process

Cibachrome: See Color, silver dye bleach print

Collodion: See Negative, collodion on glass

Collotype: See Photomechanical, collotype print

Color, additive: The principle of additive color demonstrates that all the colors of light can be made by combining different proportions of the three primary colors of light: blue, green, and red. (These colors are the complementary colors of the primary subtractive colors: yellow, magenta, and cyan.) When the three additive primary colors are mixed equally, the result is white light. Autochrome plates and color television images depend on this principle. When white light passes through a filter colored one of the primary additive colors, the filter transmits only that color of light and absorbs the other colors. Black-and-white photographic negatives exposed through such filters are called "separation negatives." Separation negatives are required in color photographic processes such as Carbro and dye imbibition.

Color, Autochrome plate: Autochromes are color transparencies on glass plates that are viewed either in special viewers called diascopes or projected onto a screen. The first practical color process, Autochromes were one of the few commercially successful additive color processes. Autochromes were made by coating a glass plate with a mosaic of minute potato starch grains dyed to approximate the primary additive colors of light. This was then coated with a panchromatic silver emulsion. The plate was placed in a camera so that the color mosaic filtered the light before it reached the emulsion layer. The development of the exposed plate thus resulted in a negative image. When the developed silver was bleached out and the plate re-exposed and redeveloped, a full-color positive image emerged. Autochrome plates were manufactured from 1907 to the 1930s by the Lumière brothers, who also figure prominently in the early history of motion pictures.

Color, chromogenic development print: A chromogenic development print is made on photographic paper that has three silver emulsion layers sensitized to the primary additive colors of light. During the developing process, dye couplers bond with the exposed and developed silver halides to produce complementary subtractive color dyes. The silver is bleached away, leaving a full-color positive image. Due to chemical impurities in the dyes, chromogenic prints are not as stable as prints made with other color printing techniques.

Color, dye imbibition print: A dye imbibition print is a color print made of dyes transferred from three gelatin matrices onto a sheet of paper coated with gelatin. To make a dye imbibition print, three separation negatives are made (see Color, additive). From these negatives, gelatin matrices are created that are capable of absorbing and releasing dyes of the primary subtractive colors. When placed in exact registration on the paper, the transferred dyes create a full-color image. The process was favored for the high degree of control over the final print image that it offered photographers. Dye imbibition prints are noted for their permanence, and the black-and-white matrix film used in the process is more stable than chromogenic color film so that new dye imbibition prints could be made many years after the original print was made.

Color, internal dye diffusion transfer print: An internal dye diffusion transfer print is a one-of-a-kind, "instant" color photograph most commonly marketed by the Polaroid corporation. The process uses a multi-layered film pack that includes an image-receiving layer, a reagent-collecting layer, and layers sensitized to the primary additive colors alternating with layers of primary subtractive color dyes. The film pack is ejected from the camera immediately after exposure, breaking open a pod of reagent that starts the development process. The exposed silver in the additive color layers blocks the diffusion of the complementary subtractive colors upward to the image-receiving layer, while the reagent-collecting layer turns opaque, masking the residual silver and dyes that did not diffuse to the image receiving layer. Dye diffusion prints are favored for the instant results they provide and for particular image manipulation techniques that are possible during the development process.

Color, silver dye bleach print: A silver dye bleach print, such as a Cibachrome print, is made on paper containing three emulsion layers, each sensitized to one of the primary additive colors of light, and each containing a full density of the complementary subtractive color dye. During development, the silver and the unnecessary dyes are selectively bleached away, leaving a final positive print. The process is used for making prints from color transparencies and is noted for its stability, image clarity, and color saturation. Interest in the process dates to the early years of the 20th century, but it wasn’t until the introduction of Cibachrome materials in 1963 that the process became widely available.

Color, subtractive: The principle of subtractive colors concerns the creation of any color by subtracting (in varying proportions) one or more of the primary subtractive colors—yellow, magenta, and cyan—from white light. The primary subtractive colors are the complementary colors of the three primary additive colors—blue, green, and red. Most modern color photography processes rely on the principle of subtractive colors.

Color transparency, chromogenic development process: A chromogenic color transparency is a positive image made on glass or film in which three silver emulsion layers sensitized to the primary additive colors are exposed to light. During the developing process, dye couplers bond to the exposed silver halides to produce complementary subtractive color dyes. The silver is bleached away, leaving a full-color positive image. The chromogenic development process is the most common contemporary color photography process and is used for negatives, transparencies, and prints. Due to chemical impurities in the dyes, chromogenic prints are not as stable as other color printing techniques.

Cyanotype: A cyanotype is a photographic print distinguished by its bright blue color. Cyanotype images are embedded in the fibers of a paper support, instead of being suspended on top as in albumen prints or gelatin silver prints. Like albumen prints and salted paper prints, cyanotypes are "printed-out," meaning that the image is created by the action of light alone on light-sensitive paper, without the use of chemical developers. The process involves soaking a sheet of paper in a solution of iron salts, then exposing the paper in contact with a negative. The part of the paper exposed to light turns blue, while the unexposed areas remain white. The image is fixed by washing the paper in water, which rinses off unexposed chemicals and intensifies the blue color. The process was invented in 1842 by Sir John Herschel.

Daguerreotype: Daguerreotypes are sharply defined, highly reflective, one-of-a-kind photographs on silver-coated copper plates, packaged behind glass and kept in protective cases. Introduced in 1839 by Louis-Jacques-Mandé Daguerre, the daguerreotype process was the first commercially successful photographic process, and is distinguished by a remarkable clarity of pictorial detail. Although early daguerreotypes required exposures of several minutes, advances in the process quickly reduced exposure times, to the relief of many sitters. Daguerreotypes were popular through the 1840s and into the 1850s, especially for portrait photography; they were primarily replaced by less-expensive and more easily viewed ambrotypes and tintypes, as well as by the improved negative-positive techniques of collodion on glass negatives and albumen prints.

Developed-out: See Gelatin silver print

Dye imbibition print: See Color, dye imbibition print

Gelatin silver print: A gelatin silver print is produced on paper coated with a gelatin emulsion containing light-sensitive silver salts. Like albumen prints, gelatin silver print images are suspended on a paper’s surface as opposed to being embedded in its fibers. Unlike albumen prints, however, gelatin silver prints are "developed-out" instead of "printed-out;" the paper registers a latent image that only becomes visible when developed in a chemical bath. The developing-out procedure allows for much shorter exposure times than printing out and results in an image less susceptible to fading. Developed at the end of the 19th century, gelatin silver printing has been the dominant black-and-white photographic process of the 20th century.

Gelatin silver glass interpositive: A gelatin silver glass interpositive is a positive image, which is made from a negative and printed on a glass plate. It serves as an intermediate stage that gives the photographer who wishes to retouch the photograph a positive image on which to work. The interpositive can be drawn on, scratched, or otherwise manipulated, then used to make another negative. The final print is made from the second negative.

Gum bichromate print: A gum bichromate print is a pigment print often characterized by a lack of precise pictorial detail and broad print tones. The process relies on the principle of bichromated colloids hardening on exposure to light. It calls for coating a sheet of paper with sensitized and pigmented gum arabic, then exposing the paper in contact with a negative, whereupon the gum hardens in proportion to the amount of light received. After exposure, the paper is soaked in water to dissolve the unhardened gum, leaving a positive image on the paper. The technique was invented in the 1850s but was largely forgotten until the 1890s when it was adopted by many Pictorialist photographers who reveled in their artistic control over the final image, often working the surface of the print with brushes in a painterly fashion. Like other pigment prints, gum bichromate prints have no light-sensitive metals susceptible to deterioration and are thus noted for their image stability and permanence.

Gum platinum print: A gum platinum print combines the fine tonal gradations found in the platinum process with the deep shadow areas possible in gum bichromate prints. To make a gum platinum print, a lightly exposed and fully developed platinum print is coated with sensitized and pigmented gum arabic and re-exposed under the same negative used to make the platinum print. The pigmented gum hardens in proportion to the amount of light it receives during exposure. The process flourished in the early part of the 20th century when many photographers engaged in complex processes that required hand-rendered manipulations in order to bolster their claims of photography’s aesthetic properties.

Kodak snapshot: The term "Kodak snapshot" applies to photographs taken with Kodak snapshot cameras introduced by the Eastman Dry Plate and Film Company (later named the Eastman Kodak Company) in 1888. These cameras had a fixed focus lens and a set shutter speed and were preloaded with roll film for 100 exposures. All that was required of photographers was to expose and advance the film. The snapshot cameras were marketed to a new and growing amateur photography market with the slogan, "You press the button, we do the rest." Indeed, once all exposures were made, the photographer sent the camera back to the factory where the pictures were printed and the camera reloaded. Both prints and camera were returned to the photographer. The term "snapshot" was first applied to photography by Sir John Herschel in 1860 to describe "the possibility... of securing a picture in a tenth of a second of time."

Lantern slide: See Transparency, gelatin on glass

Mechanical lantern slide: See Transparency, gelatin on glass

Negative, collodion on glass: Collodion on glass negatives—the dominant type of negative for much of the 19th century—are noted for greater image detail and shorter exposure times than calotype negatives. The clarity and reproducibility of collodion negatives coupled with albumen prints helped spell the demise of the daguerreotype and ambrotype as the favored processes for portrait photography. First described by Frederick Scott Archer in 1851, the process revolutionized photography in the second half of the 19th century and remained popular until about 1880, when collodion negatives were displaced by gelatin on glass negatives. Collodion on glass negatives were made by coating glass plates with collodion, a sticky substance to which light-sensitive silver salts could adhere. The sensitized plates were exposed in a camera, then developed in chemical baths. The majority of collodion on glass negatives were "wet-plate" negatives; the plate had to be coated and sensitized immediately prior to exposure and then developed shortly after exposure, before the plate could dry. This required view photographers to carry all of their chemicals and equipment with them in the field. Although ways to slow the drying time of the collodion were developed, thereby allowing the plates to be prepared farther in advance of their use, these so-called "dry-plate" collodion negatives produced inconsistent results and required longer exposure times than wet-plate negatives, hampering efforts to commercially produce and market such plates.

Negative, calotype: See Calotype negative

Negative, gelatin on glass: Gelatin on glass negatives are produced by coating glass plates with an emulsion of gelatin mixed with light-sensitive silver salts. Introduced in 1871 by Richard Leach Maddox, the process was an advancement on the collodion process, as gelatin negatives were up to ten times more sensitive to light than collodion on glass negatives. Even more important, gelatin on glass negative plates could be made well in advance of actual use, meaning that for the first time negative materials could be manufactured rather than having to be handmade. Commercially available glass plates were first manufactured in 1875, and gelatin soon displaced collodion as the dominant negative process. The convenience and availability of gelatin on glass negatives helped create the large amateur photography market in the 1880s.

Negative, gelatin on nitrocellulose sheet film: Nitrocellulose negatives are created using sheets of nitrocellulose film as a support for a light-sensitive gelatin emulsion. Efforts to find a flexible and transparent medium on which to make negatives led to the introduction of nitrocellulose roll film by the Eastman Dry Plate and Film Company in 1889. (The process was actually developed by the Reverend Hannibal Goodwin in 1887, though he didn’t receive credit for his invention until 1914.) The portability of nitrocellulose roll film compared to the cumbersome glass plates made photography increasingly convenient to amateurs. For the professional, improvements in manufacturing techniques in the early 1900s led to larger film sizes and the introduction of nitrocellulose sheet film in 1913. Because nitrocellulose is highly flammable and subject to deterioration, it was no longer used as a support material after 1950.

Oil print: An oil print is produced on a sheet of paper coated with an unpigmented bichromated colloid. After contact printing, the paper is soaked in water so that the unexposed areas absorb water and swell. The areas of the unexposed colloid that have absorbed water (the highlights) reject the application of a greasy ink that is daubed on the paper with a brush. The exposed, hardened areas of the colloid (the shadows and midtones) accept the ink, creating the final image. The process was developed in 1904 by G. E. H. Rawlins. It was used by photographers seeking greater control over the final print image than was offered by conventional photographic techniques.

Palladium print: A palladium print is similar in appearance to a platinum print with its matte surface and subtle tonal gradations. Like platinum prints, palladium print images are embedded in the fibers of the paper support, not suspended on its surface as in albumen prints or gelatin silver prints. To make a palladium print, a sheet of paper sensitized with iron salts is exposed in contact with a negative until a faint image is formed. In development, the iron salts are replaced with palladium, and the image becomes more pronounced. Commercially made palladium papers were introduced in 1916 in response to the rising cost of platinum during World War I, but the cost of palladium rose to prohibitive levels in the 1920s, and the manufacture of palladium papers ceased. Like platinum prints, palladium prints are noted for having greater stability than silver-based prints.

Photogenic drawings: See Calotype negative

Photogram: The most elemental of photographic techniques, the photogram is made without the aid of camera or lens. It is produced by placing objects in contact with the surface of sensitized paper or film and then exposing it to light. The resultant image, after processing, reveals a photographic tracing of the object’s form, with dark tonality in areas exposed to light, and light tonality in unexposed areas. Made by early practitioners such as Anna Atkins and William Henry Fox Talbot and Modernist such as Man Ray and László Moholy-Nagy, the photogram has proved to be an enduring method of discovery and transformation.

Photogravure: See Photomechanical, photogravure print

Photomechanical, collotype print: The collotype relies on the effect of light on bichromated colloids and the mutual repulsion of water and oil-based ink. To make a collotype, a printing plate is first coated with bichromated gelatin. After exposing the plate under a negative, the plate is washed in water, causing the gelatin to swell into the reticulated pattern that is the hallmark of collotypes. When the damp plate is inked, the unhardened gelatin (which forms the highlights) repels the ink, while the hardened gelatin (which forms the shadows) accepts it. The inked plate is then printed on paper. The fine reticulation of the gelatin allows for subtle midtones, often making collotypes difficult to distinguish from silver-based photographs except under magnification. The development of the collotype and other photomechanical processes in the second half of the 19th century was an important technical achievement that allowed for the distribution of photographic reproductions in books.

Photomechanical, photogravure print: Photogravure printing is a form of intaglio printing, in which a photographic image is chemically etched into a copper plate. When the plate is inked, then wiped clean, the ink remains in the pits of the plate and is transferred to a sheet of paper during the printing process. In the photogravure process, the printing plate is first dusted with a resin, creating a random dot structure that allows for the continuous tones of the original photograph to be reproduced. The plate is then coated with bichromated gelatin and exposed in contact with a positive photographic transparency. The printing plate is etched in those areas where the gelatin remains unhardened (forming the shadows), but not in those areas where the gelatin hardens (forming the highlights). William Henry Fox Talbot experimented with photogravure as early as 1852, but the process was not widely used until the 1870s, when Karl Klic developed a way of satisfactorily dusting the plates with resinous powder. Around the turn of the 20th century, photogravure was embraced by Pictorialist photographers who admired the beautiful reproductions the process allowed. Perhaps the ultimate achievement of photogravure printing is to be found in the pages of Camera Work, published by the photographer Alfred Stieglitz from 1903 to 1917.

Photomechanical, Woodburytype: Woodburytypes are distinguished from other photomechanical processes by the fact that it is a continuous-tone image. The process involves exposing unpigmented bichromated gelatin in contact with a negative. The gelatin hardens in proportion to the amount of light received. When the gelatin is washed, the unexposed portion dissolves, leaving a very fine and hard relief of the image. Under extremely high pressure, this relief is pressed into a sheet of soft lead, producing a mold of the image. This mold is then filled with pigmented gelatin and transferred to paper during printing. The process was invented in 1864 by Walter Woodbury and achieved acclaim for its exquisite rendering of pictorial detail and its permanency.

Physionotrace engraving: A physionotrace is made by the use of a mechanical system that scratches a profile onto a copper plate as the operator traces a sitter’s profile cast on a sheet of glass. After tracing the profile, features can be added to the plate, which is then inked and printed. Invented in 1786 by Gilles-Louis Chrétien, the process was the first mechanical means for making multiple prints of a portrait.

Pigment print: A pigment print involves any one of a number of photographic processes (such as carbon prints and gum bichromate prints) that utilize pigments and bichromated colloids rather than light-sensitive metal salts in the creation of print images. Pigment printing processes were first developed in the 1850s and were popular because they were more permanent than metal-based processes. They also allowed for a greater control of the appearance of the final print image.

Platinum/palladium print: A platinum/palladium print combines platinum and palladium solutions in order to conserve the amount of the more expensive platinum used to make the print. See platinum print for more information.

Platinum print: A platinum print is distinguished by its matte surface and subtle tonal gradations. Like salted paper prints, platinum print images are embedded in the fibers of the paper, not suspended on the surface of the paper support. To make a platinum print, a sheet of paper sensitized with iron salts is exposed in contact with a negative until a faint image is formed. In development, the iron salts are replaced with platinum, and the image becomes more pronounced. Because of the tonal range and surface quality of platinum prints, many fine art photographers of the late 19th and early 20th century preferred the process over gelatin silver prints. The platinum printing process was developed in the 1870s, and commercially made platinum papers were available until the rising costs of platinum during World War I made the process prohibitively expensive. Platinum prints were replaced by the similar, but less-expensive, palladium prints. Platinum prints are the most stable of all the metal-based prints.

Polaroid print: See Color, internal dye diffusion transfer print

Printing-out: See Albumen print, Cyanotype, or Salted paper print

Salted paper print: Salted paper prints were the earliest photographic prints on paper. They are often distinguished by their lack of precise image details and matte surface. Salted paper print images are embedded in the fibers of the paper, instead of being suspended on the surface of the paper, as in the later albumen prints and gelatin silver prints. Salted paper prints were "printed-out" in contact with paper negatives; the image was formed solely by the action of light on metal salts, without chemical developers. The printing-out process required long exposure times for producing a positive print. The process for making salted paper prints was developed by William Henry Fox Talbot in the 1830s, and salted paper prints were common until the mid-1850s, when they were eclipsed in popularity by albumen prints.

Silver dye bleach print: See Color, silver dye bleach print

Stereograph: A stereograph comprises two nearly identical photographic prints that have been recorded with a specially designed camera that has two lenses that are eye-width apart. Stereograph negatives are exposed simultaneously and later printed on heavy card stock. When a stereograph is viewed through a special viewer called a stereoscope, the viewer sees the image with a third dimension, giving a sense of depth and "reality" to the scene. They were a popular form of entertainment from the 1850s to the 1920s. In the 20th century stereography found renewed popularity in the form of Viewmaster reels and viewers.

Subtractive color: See Color, subtractive

Tintype: A tintype is a non-reflective, one-of-a-kind photograph on a sheet of iron coated with a dark enamel. Its most common use was for portrait photography. Like ambrotypes, tintypes rely on the principle that underexposed collodion negatives appear as positive images when viewed against a dark background. Less expensive and more durable than either ambrotypes or daguerreotypes, tintypes did not require protective cases and were often kept in simple paper frames or folders. Tintypes first appeared in the United States in 1856, and remained popular well into the 20th century.

Transparency, gelatin on glass (lantern slide): A lantern slide is a gelatin silver positive image on a glass plate that is projected onto a screen with the use of a slide projector, or "magic lantern." Before photography, lantern slide images were either stenciled or drawn, but in the 1850s, photographic lantern slides with albumen positive images became available. Beginning in the 1870s, gelatin silver lantern slides were commercially produced to meet the ever-increasing public demand. Lantern slides were used for popular entertainment, education, scientific study, and travelogues.

Transparency, gelatin on glass (mechanical lantern slide): A mechanical lantern slide is two or more separate lantern slides in one holder or frame. The movement of one slide over a second slide produces motion or the appearance of motion when projected onto a screen.

Woodburytype: See Photomechanical, Woodburytype