HISTORICAL NOTE

each 2 1/z inches in diameter. Once a pho• tographer exposed all the film, he returned Pretty as a Picture the entire camera to one of the two East• man factories (in Rochester, New York, or Harrow, Middlesex), where the film would Part 2: Photographic Film Materials be developed and printed. The photogra• pher received his prints and his camera and Color Photography back, fully loaded once more. Thomas A. Edison was one of their-first and best cus• tomers. In 1891 a new Kodak camera appeared, this time with "celluloid" film (a trade Last month's Historical Note discussed messy and complicated. Eastman at• name for cellulose nitrate in solid solution the birth of photographic processes and tempted to make a flexible transparent film with a plasticizer and a flame-retardant) the various materials used in capturing from cellulose nitrate (or collodion, which wound on a wooden core inside a light• black-and-white images. All these proc• had been used to coat glass plates a decade tight box. The film was backed with black esses were messy and time-consuming, re• or so before), but this resulted in films that paper, and black cloth leaders were at• quiring photographers to carry chemical were too thin for practical use. When it was tached to each end. This allowed photogra• supplies to coat their own photographic discovered that wood alcohol could be a phers to change film quickly and easily and plates before each exposure and then de• solvent for cellulose nitrate, much im• return only the film pack for processing. In velop them immediately. By the 1880s, in• proved plastic films were possible. In 1888, 1903, Eastman further improved the film ventors were searching for a convenient ]. Carbutt introduced photographic emul• support by coating the back with plain gel• method to supply pre-made plates that sions on sheets of plastic collodipn cut atin. This kept the developed negative could be stored, used, and developed at from blocks. The following year Eastman from curling, making it easier to print, han• the photographer's leisure. marketed commercial film on rolls of trans• dle, and store. A century ago this year, the American parent cellulose nitrate. The formation of photographic film in inventor George Eastman introduced rolls Although this type of film was patented long celluloid rolls made possible the crea• of flexible photographic film and portable independently in 1887 by the Rev. Hanni• tion of the motion picture. In 1923 the first cameras to use them, which revolutionized bal Goodwin, Eastman used it in his first 16-mm film was made available, packaged photography and made it available to the portable roll-film camera, the "Kodak No. in canisters that could be loaded into mo• general public. This Historical Note will 1:' He realized that convenience and sim• tion picture cameras without requiring a discuss the rise of flexible film supports for plicity would be the key to making photog• darkroom. In 1932 a similar film only 8 mm photographic emulsions and also look at raphy available to the mass public, rather wide came into use. the introduction of color films. than to just the few avid hobbyists willing However, celluloid film was very flam• The availability of ready-made dry pho• to put up with the mess and the complica• mable (cellulose nitrate is, after all, another tographic plates was a vast improvement, tions. When he introduced the Kodak cam• chemical form of guncotton), and this cre• but the weight and fragility of the glass era, Eastman backed it with an aggressive ated hazards in its use and storage in large plates caused many problems for photog• advertising campaign-"You press the but• quantities. In 1909 Eastman first intro• raphers. Amateur inventors tried to find ton, we do the rest" was their slogan. duced "safety" film made of cellulose ace• lighter and more flexible substitutes to sup• tate instead of the cellulose nitrate for the port the photographic emulsion. plastic base. This slow-burning film re• In 1884 American inventors George placed celluloid for motion pictures. In Eastman and W. H. Walker introduced Charles Cros and Louis 1937 the Eastman Kodak company further rolls of sensitized paper coated with a gela• Ducos du Hauron made improved the safety film by switching to tin emulsion. The rolls of paper were cellulose acetate propionate; in 1948 they loaded into the roll holder mounted in the the first color photo• changed the plastic formula again to ap• position of a camera's plate-holder. graphs in 1869, using a proach cellulose triacetate. In 1950 all Ko• Eastman had begun photography as a dak film, for all uses, was made on the hobby while he was working for ·a bank, film composed of three slow-burning plastic base, and other man• but in 1879 he developed a machine that layers of colored gelatin ufacturers followed suit. could apply gelatin emulsion to glass lo some special cases different polymers plates, making possible the commercial (yellow, blue, and red). were used for plastic backing, especially manufacture of dry plates. He patented the Each layer of gelatin when dimensional stability was particu• machine several years later and formed the larly important, such as in mapping and Eastman Dry Plate and Film Company. He served as a monochro• graphic arts. Some of these other plastics introduced his rolled-paper film the same matic transparency that were polyvinylchloride and its copoly• year. mers, polystyrene, polycarbonate, and At first, Eastman greased the paper to combined to form a full• some polyesters. reduce the printing t1me necessary, but later he used a soluble gelatin coated with a spectrum image. Color Film gelatin emulsion on temporary paper; the Since the beginnings of photography, entire coating could be stripped off the inventors searched for a way to take pic• opaque paper and transferred to a glass At the factory, the Kodak camera was tures that would capture the color, and not plate after development. loaded with a roll of photographic film, just the light and dark tones, of a subject. However, this stripping process was enough to make 100 circular exposures, In 1810 German physicist Thomas Johann

54 MRS BULLETIN/JUNE 1989 HISTORICAL NOTE

Seebeck found that wet silver chloride re• coupled to each layer during developing. Four years after the non wandering dyes tained some faint colors of a spectrum to B. Homolka had discovered that when cer• appeared, a film based on Fischer's dye• which it was exposed. However, the colors tain developers react with silver halide to coupling principle became commercially faded when the silver chloride dried. Oth• form silver in the presence of a "coupling" available as "Kodachrome;' developed by ers attempted unsuccessfully to make this compound, a dye image is also formed in Leopold Mannes and Leopold Godowsky. technique practical. proportion to the original silver image. The The controlled-diffusion developing proc• In 1861 British physicist James Clerk silver is then bleached out, leaving only the ess was complicated, but resulted in good Maxwell attempted color reproduction in a dye image. color quality. Kodachrome film was first re• completely different way. He applied his leased as 16-mm motion picture film, but new theories on color vision that all colors then became available in 35-mm format for could be obtained by mixing red, green, or slides and later for 8-mm motion picture blue light in proper proportions. In a fa• The formation of photo• film and sheet film. mous experiment, Maxwell made three At about the same time the Agfa Com• wet-collodion photographs of a group of graphic film in long pany in Germany released Agfacolor Neu colored ribbons, each through a red, celluloid rolls made pos• film, which was similar to Kodachrome but green, or blue filter. He made transparent processed differently. Whereas the three black-and-white positives, which he then sible the creation of the layers in Kodachrome film contained silver projected through the appropriate red, motion picture. In 1923 emulsions and sensitizing dyes, Agfacolor green, or blue filter. All three images were had "color formers" in each layer as well. then superimposed on the screen, result• the first 16-mm film was Agfacolor film was developed by a system ing in a reasonable reproduction of the rib• made available, pack• of controlled-penetration developers that bons' original colors. (This process turned created the appropriate color in each layer out to be impractical at the time, though, as aged in canisters that in a processing single step. While Koda• wet-collodion photography had very little could be loaded into chrome processing was complicated and sensitivity in the red and green portions of had to be done in a large facility with auto• the spectrum:) motion picture cameras matic machinery, amateur photographers Charles Cros and Louis Ducos du without requiring a could develop their own Agfacolor film. Hauron made the first color photographs Other systems appeared later, including in 1869, using a film composed of three lay• darkroom. the Kodacolor, Ektacolor, and Ektachrome ers of colored gelatin (yellow, blue, and processes, which also used nondiffusing red). Each layer of gelatin served as a dye-couplers. These couplers were not dis• monochromatic transparency that com• By proper selection of the coupling com• persed directly in the emulsions, but dis• bined to form a full-spectrum:image. Du pound and the developer, Fischer showed solved in an oily liquid sprayed on the Hauron also proposed that such photo• that a great many colors could be obtained. emulsion in fine droplets. Kodacolor Aero graphs could be printed using a pigment The final dyes are of the indoaniline or azo• Reversal film was the first film of this type, process. After some improvements, their methine types. For the three complemen• introduced in 1940 for aerial photography technique became the basis for color print• tary colors used in this process (cyan, by the U.S. Army, and could be developed ing processes from the 1890s onward. magenta, and yellow), phenols are usually directly in the field. Some early attempts at color film used used to couple with cyan dyes, nitriles or Since then, many different photographic tiny blue, green, and red filter elements pyrazolones for magenta dyes, and esters, materials have been created to address spe• dispersed through the emulsion rather ketones, or amides for yellow dyes. cific needs in engineering, science, cartog• than three separate layers that had to be Fischer proposed a film using three su• raphy, and graphic arts. New films are developed separately. The first successful perimposed layers, each containing the ap• being developed to be sensitive in very nar• use of this "screen process" was demon• propriate couplers that would affix the row ranges of the spectrum, and to operate strated by J. Joly and J. W. MacDonough in proper dyes during developing. He could well beyond the visible range, as well as 1892, who placed their filter elements on a not make his idea work, however, because those requiring shorter exposure times and separate plate from the negative. Later, the the couplers and sensitizing dyes kept providing less graininess for extremely "Lumiere Autochrome" photographic wandering from their own layers. Not until high-resolution images. Rarely has a single plate used a filter layer of dyed starch 1931 did nonwandering sensitizing dyes invention opened up so many different grains interspersed with carbon black. become available. windows for progress. In 1897 Ducos du Hauron patented the KEVIN J. ANDERSON idea of making a color film with three su• perimposed emulsion layers (red, green, and blue), but it was not until 1912 that a viable method for this technique was dis• covered by the German chemist Rudolf Fischer. Fischer showed that "dye• Coming in the July MRS BULLETIN... coupling" developers could be used to make colored images from silver emul• Focus on Fusion Materials sions, and proposed that they be used in a multilayer film. Theodore Reuther, Guest Editor lf each emulsion layer is complementary and inseparable from the others, different dyes of the appropriate colors could be

MRS BULLETIN/JUNE 1989 55