Film stock
Film stock is a type of photographic film that is used for recording motion pictures or animation. It is recorded on by a movie camera, developed, edited, and projected onto a screen using a movie projector.
Photographic film consists of a long strip of transparent plastic film base, coated on one side with a photographic emulsion: a mixture of gelatin and microscopic light-sensitive silver halide crystals. A very short exposure is made, producing an invisible latent image in the emulsion, which can be chemically developed into a visible photograph.
Most movie film records a negative image and a reversed print onto another reel of film is needed to project from. Many commercially recorded films use a digital intermediate step, in which film is scanned digitally for editing, and either printed from the digital file onto a positive reel with a film recorder, or projected digitally. Alternatively, "reversal film" can be used, which records a positive image.
In black and white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which blocks light and appears as the black part of the film negative. Color film has at least three sensitive layers. Dyes, which adsorb to the surface of the silver salts, make the crystals sensitive to different colors. Typically the blue-sensitive layer is on top, followed by the green and red layers. During development, the exposed silver salts are converted to metallic silver, just as with black-and-white film. But in a color film, the by-products of the development reaction simultaneously combine with chemicals known as color couplers that are included either in the film itself or in the developer solution to form colored dyes. Because the by-products are created in direct proportion to the amount of exposure and development, the dye clouds formed are also in proportion to the exposure and development. Following development, the silver is converted back to silver salts in the bleach step. It is removed from the film in the fix step and is sometimes recovered for subsequent use or sale. Fixing leaves behind only the formed color dyes, which combine to make up the colored visible image. Later color films, like Kodacolor II, have as many as 12 emulsion layers, with upwards of 20 different chemicals in each layer. Photographic film and film stock tend to be similar in composition and speed, but often not in other parameters such as frame size and length.
History
1888–1899: Before standardization
Early motion picture experiments in the 1880s were performed using a fragile paper roll film, with which it was difficult to view a single, continuously moving image without a complex apparatus. The first transparent and flexible film base material was celluloid, which was discovered and refined for photographic use by John Carbutt, Hannibal Goodwin, and George Eastman. Eastman Kodak made celluloid film commercially available in 1889; Thomas Henry Blair, in 1891, was his first competitor. The stock had a frosted base to facilitate easier viewing by transmitted light. Emulsions were orthochromatic. By November 1891 William Dickson, at Edison's laboratory, was using Blair's stock for Kinetoscope experiments. Blair's company supplied film to Edison for five years. Between 1892 and 1893, Eastman experienced problems with production. Because of patent lawsuits in 1893, Blair left his American company and established another in Britain. Eastman became Edison's supplier of film.Blair's new company supplied European filmmaking pioneers, including Birt Acres, Robert Paul, George Albert Smith, Charles Urban, and the Lumière Brothers. By 1896, the new movie projector required a fully transparent film base that Blair's American operation could not supply. Eastman shortly thereafter bought the company out and became the leading supplier of film stock. Louis Lumière worked with Victor Planchon to adapt the Lumière "Blue Label" photographic plate emulsion for use on celluloid roll film, which began in early 1896.
Eastman's first motion picture film stock was offered in 1889. At first the film was the same as photographic film. By 1916, separate "Cine Type" films were offered. From 1895, Eastman supplied their motion picture roll film in rolls of 65 feet, while Blair's rolls were 75 feet. If longer lengths were needed, the unexposed negative rolls could be cemented in a darkroom, but this was largely undesirable by most narrative filmmakers. The makers of Actuality films were much more eager to undertake this method, however, in order to depict longer actions. They created cemented rolls as long as 1,000 feet. American Mutoscope and Biograph was the first known company to use such film for the Jeffries-Sharkey fight on 3 November 1899.
1900–1919: Toward the standard picture film
As the quantity of film and filmmakers grew, the demand for standardization increased. Between 1900 and 1910, film formats gradually became standardized and film stocks improved. A number of film gauges were made. Eastman increased the length of rolls to 200 feet without major adjustments to the emulsion, retaining a large market share. Lumière reformulated its stock to match the speed of Eastman film, naming it 'Etiquette Violette'. Blair sold his English company to Pathé in 1907 and retired to the US. Pathé began to supplement its operation in 1910 by purchasing film prints, stripping the emulsion from the film base and re-coating it. 35mm film began to become the dominant gauge because of the commonality of Edison's and Lumière's cameras. Consumers usually purchased unperforated film and had to punch it by perforators that were often imprecise, causing difficulty in making prints for the opposite perforation format. In 1908, the perforators began to be made by Bell and Howell. Eastman Kodak used the Bell and Howell machine to perforate its films. In 1909, Edison's organization of the Motion Picture Patents Trust agreed to what would become the standard: 35 mm gauge, with Edison perforations and a 1.33 aspect ratio.Image:16mmBWrevDP.png|thumb|A silent home movie on 16mm black-and-white reversal double-perforation film stock
Agfa began to produce motion picture film in 1913, but remained a largely local supplier until World War I boycotts of popular French, American and Italian film stocks allowed the UFA film studio to flourish, boosting Agfa's orders. All film stocks were manufactured on a nitrate film base, which is highly flammable. Nitrate film fires were virtually impossible to extinguish. A significant number of fatal accidents occurred in theatrical projection booths, where the heat of the projector lamp made ignition a possibility. Amateur filmmaking slowly developed during this period. Kodak developed a heat-resistant 'safety base' for home projection.
In 1909, tests showed cellulose diacetate to be a viable replacement base, and Kodak began selling acetate-base films the following year in 22 mm widths for Edison's work on the Home Kinetoscope, which was commercially released in 1912. Eastman Kodak introduced a non-flammable 35 mm film stock in 1909. The plasticizers used to make the film flexible evaporated quickly, making the film dry and brittle, causing splices to part and perforations to tear. In 1911 the major American film studios returned to using nitrate stock. More amateur formats began to use acetate-based film, and several, including Kodak's own 16 mm format, were designed specifically to be manufactured with safety base. Kodak released Cine Negative Film Type E in 1916 and Type F in 1917. As both of these orthochromatic films were no faster than previous offerings, the improvements were in granularity and sharpness.
1920s: Diversification of film sensitivity
Film stock manufacturers began to diversify their products. Each manufacturer had previously offered one negative stock and one print stock. In 1920, a variant of Type F film known as X-back was introduced to counteract the effects of static electricity on the film, which can cause sparking and create odd exposure patterns on the film. A resin backing was used on the film, which rendered the film too opaque to allow focusing through the back of the film, a common technique for many cameras of that era. The X-back stock was popular on the east coast of the US. Other manufacturers were established in the 1920s, including American E.I. Dupont de Nemours in 1926 and Belgian Gevaert in 1925. Panchromatic film stock became more common. Created in 1913 for use in early color film processes such as Kinemacolor, panchromatic was first used in a black-and-white film for exterior sequences in Queen of the Sea and originally available as a special order product. The stock's increased sensitivity to red light made it an attractive option for day for night shooting. Kodak financed a feature in 1922, shot entirely with panchromatic stock, The Headless Horseman, to promote the film when Kodak introduced it as a standard option. Panchromatic film stock increased costs and no motion pictures were produced on it in their entirety for several years. The cross-cutting between panchromatic and orthochromatic stocks caused continuity problems with costume tones and panchromatic film was often avoided.Orthochromatic film remained dominant until the mid-1920s due to Kodak's lack of competition in the panchromatic market. In 1925, Gevaert introduced an orthochromatic stock with limited color sensitivity and a fully panchromatic stock, Pan-23. In 1926, Kodak lowered the price of panchromatic stock to parity with its orthochromatic offering and the panchromatic stock began to overtake the orthochromatic stock's market share within a few years. As similar panchromatic film stocks were also manufactured by Agfa and Pathé, making the shift to panchromatic stocks largely complete by 1928, Kodak discontinued orthochromatic stock in 1930.