Photographic Processes Video Series & Glossary
The George Eastman Museum photography collection is among the best and most comprehensive in the world. Learn more about the major types of photographic processes, from early daguerreotypes to digital prints.
From the ancient discovery of the camera obscura to the 18th century mechanical devices used to create silhouettes such as the physionotrace, this initial chapter explores the inventions and inventors that preceded photography. It recreates the experiments of Johann Schulze who proved the light sensitivity of certain silver salts and Thomas Wedgwood’s early attempts to make photographic images. These early pioneers contributed to the discovery of photography in 1839.
Daguerreotypes are sharply defined, highly reflective, one-of-a-kind photographs on silvercoated copper plates, usually packaged behind glass and kept in protective cases. The first commercially successful photographic process, the daguerreotype was popular through the 1840s and into the 1850s, especially for portrait photography. They were primarily replaced by less-expensive ambrotypes and tintypes, as well as by the improved negative-positive techniques of collodion-on-glass negatives and albumen silver prints.
Talbot's Processes: Photogenic Drawing, Salted Paper Print and Calotype Negative
The calotype negative was the first to rely on the chemical development of a latent image on light-sensitive paper that had been exposed in a camera. Patented in England in 1841 by William Henry Fox Talbot, the process was an advancement on Talbot’sfirst 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 photographic printing. Calotype negatives were popular during the 1840s for architectural and view photography, though they were largely replaced by collodionon-glass negatives in the mid-1850s.
Sir John Herschel invented the cyanotype in 1842. The process depends on the photochemical reduction of ferric salts into ferrous salts leading to the formation of Prussian blue, an iron-based pigment. The process was used sporadically throughout the 19th century and more frequently in the twentieth century for the reproduction of architectural plans and technical drawings, called “blueprints."
The Collodion Process
Introduced in 1851, by Frederick Scott Archer, the wet collodion process was a fairly simple, if somewhat cumbersome photographic process. A 2% solution of collodion, bearing a very small percentage of potassium iodide, was poured over a plate of glass, leaving a thin, clear film containing the halide. The plate was then placed in a solution of silver nitrate. When removed from the silver, the collodion film contained a translucent yellow compound of light-sensitive silver iodide. The plate was exposed still wet and then developed by inspection under red light. Once the plate was washed and dried, it was coated with a protective varnish. The collodion process replaced the daguerreotype as the predominant photographic process by the end of the 1850’s. It was eventually replaced in the 1880’s with the introduction of the gelatin silver process.
Ambrotypes are sharply detailed, one-of-a-kind photographs on glass, packaged in protective cases. 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.
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 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 ambrotypes and 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 twentieth century.
The Albumen Silver Print
Invented in 1850, the albumen silver print was the most popular photographic printing process of the nineteenth century. A sheet of paper is coated with albumen (egg white) and salts, and then sensitized with a solution of silver nitrate. The paper is exposed in contact with a negative and printed out, meaning the image is created solely by the action of light on the sensitized paper without any chemical development Because the paper is coated with albumen, the silver image is suspended on the surface rather than absorbed into the paper fibers, resulting in a sharp image with fine detail on a smooth, glossy surface.
The Platinum Print
Platinum prints are characterized by their delicate surface and subtle tonal gradations. They are made by sensitizing paper with iron salts and exposing the paper in contact with a negative until a faint image has formed. The paper is then chemically developed in a process that replaces the iron salts with platinum and intensifies the image. Platinum prints were popular with art photographers around the turn of the twentieth century, but when World War I caused the price of platinum to rise, palladium (a related metallic element) was introduced as a more affordable substitute.
The Pigment Processes
Developed in the 1850s but not used widely until the late nineteenth century, the gum bichromate printing process is a type of pigment print made by coating a sheet of paper with sensitized and pigmented gum arabic. Exposed in contact with a negative, the gum hardens on areas where light reaches the paper. Next, the unexposed gum is washed away, leaving a positive image on the paper. The images can be manipulated further with brushes and water, and can be coated and exposed again to attain multiple layers of color. The resulting prints are characterized by broad tones and soft detail, sometimes resembling paintings or drawings.
Bromoil Transfer Print
The oil printing process, developed in 1904, is based on the fact that oil and water do not mix. First, a sheet of paper is coated with an unpigmented bichromated gelatin solution. When the paper is exposed in contact with a negative, the exposed areas harden. After exposure, the paper is soaked in water, and the unexposed areas absorb water and reject greasy inks that are applied to the paper with a brush. The ink is accepted by the hardened, exposed areas, forming the image. Developed in 1907, bromoil printing is a modification of this process using gelatin bromide paper. After making a positive enlargement on a sheet of bromide paper, the print is bleached to remove the silver image, leaving a gelatin layer hardened and ready to receive the application of ink.
Woodburytypes are distinguished from other photomechanical processes by the fact that they are continuous-tone images. 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 behind a 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. Invented in 1864 by Walter Woodbury, the process was acclaimed for its exquisite rendering of pictorial detail as well as its permanency.
The Gelatin Silver Process
Introduced at the end of the nineteenth century, gelatin silver prints dominated black-and-white photography in the twentieth century. The paper used to make gelatin silver prints is coated with an emulsion that contains gelatin and silver salts. Gelatin silver prints are developed out rather than printed out, which means that exposure to light registers a latent image on the paper that becomes visible only when developed in a chemical bath.
Photography’s earliest practitioners dreamed of finding a method for reproducing the world around them in color. Some 19th century photographers experimented with chemical formulations aimed at producing color images by direct exposure, while others applied paints and powders to the surfaces of monochrome prints. Vigorous experimentation led to several early color processes, some of which were even patented, but the methods were often impractical, cumbersome and unreliable. This chapter explores early additive color processes as well as later subtractive processes like chromogenic color and the Kodachrome.
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 (red, green, and blue). During the developing process, dye couplers bond with the exposed and developed silver halides to produce complementary subtractive color dyes (cyan, magenta, and yellow). 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, such as silver dye bleach prints.
Silver Bleach Dye Print
A silver dye bleach 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. Although interest in the process dates to earlier in the twentieth century, it was not widely available until the introduction of Cibachrome materials in 1963.
Kodak engineer Steven Sasson invented the digital camera in 1975. Within 25 years the technology would overtake analog film materials and dominate the photographic industry and practice. This chapter features a timeline of digital camera technology starting with Steven Sasson’s first completely digital camera prototype and takes us all the way to the smart phones of today.
Videos made possible by a grant from the U.S. Institute of Museum and Library Services, grant number MA-10-13-0194.