Duplitized film was a type of motion picture print film stock used for some two-color natural color processes. It was introduced by Eastman Kodak around 1913. The stock was of standard gauge and thickness, but it had a photographic emulsion coated on both sides of the film base instead of on one surface only.
In color film processes such as Cinecolor and Prizma, two black-and-white negatives photographed through red and blue-green filters, or by an equivalent bipack method, were photographically printed onto opposite sides of the duplitized film. Because its emulsion was sensitive only to blue light, a temporary yellow dye incorporated into the film prevented each printing light from also exposing the emulsion on the other side. The exposed film was developed like ordinary black-and-white film, producing a series of black-and-white silver images on each side. These were then chemically converted into single-color images of a color roughly complementary to that being used for the images on the other side and to the color of the camera filter used when filming them. The resulting superimposed pairs of transparent single-color images, projected onto a screen or viewed directly, could reproduce a limited but useful and sometimes very pleasing range of color. It was mainly in the specifics of the chemistry, apparatus and procedures used to convert the silver images into color-toned ones that the several commercial processes based on the use of duplitized film differed significantly.
Large sheets of duplitized film were sometimes used for medical X-ray photography. The double emulsion increased the overall sensitivity of the film, reducing the X-ray exposure required. Duplitized film of any kind was not suitable for ordinary camera use, due to the loss of image quality that would result from the light becoming diffused as it passed through the several layers, but with X-ray shadows that was not a problem.
Film stock is an analog medium 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. It is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast and resolution of the film. The emulsion will gradually darken if left exposed to light, but the process is too slow and incomplete to be of any practical use. Instead, a very short exposure to the image formed by a camera lens is used to produce only a very slight chemical change, proportional to the amount of light absorbed by each crystal. This creates an invisible latent image in the emulsion, which can be chemically developed into a visible photograph. In addition to visible light, all films are sensitive to X-rays and high-energy particles. Most are at least slightly sensitive to invisible ultraviolet (UV) light. Some special-purpose films are sensitive into the infrared (IR) region of the spectrum.
Photography is the art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed in many fields of science, manufacturing, and business, as well as its more direct uses for art, film and video production, recreational purposes, hobby, and mass communication.
The following list comprises significant milestones in the development of photography technology.
Photographic paper is a paper coated with a light-sensitive chemical formula, like photographic film, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image that is then developed to form a visible image; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver halide but other alternatives have also been used.
An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives, or from transparencies.
Photographic printing is the process of producing a final image on paper for viewing, using chemically sensitized paper. The paper is exposed to a photographic negative, a positive transparency , or a digital image file projected using an enlarger or digital exposure unit such as a LightJet or Minilab printer. Alternatively, the negative or transparency may be placed atop the paper and directly exposed, creating a contact print. Digital photographs are commonly printed on plain paper, for example by a color printer, but this is not considered "photographic printing".
C-41 is a chromogenic color print film developing process introduced by Kodak in 1972, superseding the C-22 process. C-41, also known as CN-16 by Fuji, CNK-4 by Konica, and AP-70 by AGFA, is the most popular film process in use, with most, if not all photofinishing labs devoting at least one machine to this development process.
In infrared photography, the photographic film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum.
Panchromatic emulsion is a type of black-and-white photographic emulsion that is sensitive to all wavelengths of visible light. By extension, a panchromatic sensor is an image sensor sensitive to the whole visible spectrum. A panchromatic image is the resulting picture.
The science of photography is the use of chemistry and physics in all aspects of photography. This applies to the camera, its lenses, physical operation of the camera, electronic camera internals, and the process of developing film in order to take and develop pictures properly.
Cinecolor was an early subtractive color-model two-color motion picture process that was based upon the Prizma system of the 1910s and 1920s and the Multicolor system of the late 1920s and the 1930s. It was developed by William T. Crispinel and Alan M. Gundelfinger, and its various formats were in use from 1932 to 1955.
In photography, toning is a method of altering the color of black-and-white photographs. In analog photography, it is a chemical process carried out on metal salt-based prints, such as silver prints, iron-based prints, or platinum or palladium prints. This darkroom process cannot be performed with a color photograph. The effects of this process can be emulated with software in digital photography. Sepia is considered a form of black-and-white or monochrome photography.
In cinematography, bipacking, or a bipack, is the process of loading two reels of film into a camera, so that they both pass through the camera gate together. It was used both for in-camera effects and as an early subtractive colour process.
Color motion picture film refers both to unexposed color photographic film in a format suitable for use in a motion picture camera, and to finished motion picture film, ready for use in a projector, which bears images in color.
Dufaycolor is an early British additive colour photographic film process, introduced for motion picture use in 1932 and for still photography in 1935. It was derived from Louis Dufay's Dioptichrome plates, a glass-based product for colour still photography, introduced in France in 1909. Both Dioptichrome and Dufaycolor worked on the same principles as the Autochrome process, but achieved their results using a layer of tiny colour filter elements arrayed in a regular geometric pattern, unlike Autochrome's random array of coloured starch grains. The manufacture of Dufaycolor film ended in the late 1950s.
In motion pictures, Kodak's Kodacolor brand was originally associated with an early lenticular color motion picture process, first introduced in 1928 for 16mm film. The process was based on the Keller-Dorian system of color photography.
Dye transfer is a continuous-tone color photographic printing process. It was used to print Technicolor films, as well as to produce paper colour prints used in advertising, or large transparencies for display.
In bipack color photography for motion pictures, two strips of black-and-white 35 mm film, running through the camera emulsion to emulsion, are used to record two regions of the color spectrum, for the purpose of ultimately printing the images, in complementary colors, superimposed on one strip of film. The result is a multicolored projection print that reproduces a useful but limited range of color by the subtractive color method. Bipack processes became commercially practical in the early 1910s when Kodak introduced duplitized film print stock, which facilitated making two-color prints.
Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and resolution of the film. Film is typically segmented in frames, that give rise to separate photographs.
Technicolor is a series of color motion picture processes, the first version dating back to 1916, and followed by improved versions over several decades.
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