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.
Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image into a visible image, makes this permanent and renders it insensitive to light.
Photographic paper is a paper coated with a light-sensitive chemical, 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, and functions similarly to photographic film. The most common chemistry used is gelatin silver, but other alternatives have also been used.
In the processing of photographic films, plates or papers, the photographic developer is one or more chemicals that convert the latent image to a visible image. Developing agents achieve this conversion by reducing the silver halides, which are pale-colored, into silver metal, which is black when in the form of fine particles. The conversion occurs within the gelatine matrix. The special feature of photography is that the developer acts more quickly on those particles of silver halide that have been exposed to light. When left in developer, all the silver halides will eventually be reduced and turn black. Generally, the longer a developer is allowed to work, the darker the image.
The albumen print, also called albumen silver print, is a method of producing a photographic print using egg whites. Published in January 1847 by Louis Désiré Blanquart-Evrard, it was the first commercial process of producing a photo on a paper base from a negative, previous methods - such as the daguerreotype and the tintype - having been printed on metal. It became the dominant form of photographic positives from 1855 to the start of the 20th century, with a peak in the 1860–90 period. During the mid-19th century, the carte de visite became one of the more popular uses of the albumen method. In the 19th century, E. & H. T. Anthony & Company were the largest makers and distributors of albumen photographic prints and paper in the United States.
The gelatin silver process is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating.
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.
Silver bromide (AgBr) is a soft, pale-yellow, water-insoluble salt well known for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgBr is widely used in photographic films and can be found naturally as the mineral bromargyrite.
A silver halide is one of the chemical compounds that can form between the element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine with silver to produce silver bromide (AgBr), silver chloride (AgCl), silver iodide (AgI), and four forms of silver fluoride, respectively.
In photography, reciprocity is the inverse relationship between the intensity and duration of light that determines the reaction of light-sensitive material. Within a normal exposure range for film stock, for example, the reciprocity law states that the film response will be determined by the total exposure, defined as intensity × time. Therefore, the same response can result from reducing duration and increasing light intensity, and vice versa.
Silver chloride is an inorganic chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water and its sensitivity to light. Upon illumination or heating, silver chloride converts to silver, which is signaled by grey to black or purplish coloration in some samples. AgCl occurs naturally as the mineral chlorargyrite.
A sensitivity speck is a place in silver halide crystal where latent image is preferentially formed. This is very often the site of shallow electron traps, such as crystalline defect and silver sulfide specks created by sulfur sensitization process.
Film grain or film granularity is the random optical texture of processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons. While film grain is a function of such particles it is not the same thing as such. It is an optical effect, the magnitude of which depends on both the film stock and the definition at which it is observed. It can be objectionably noticeable in an over-enlarged film photograph.
A chromogenic print, also known as a C-print or C-type print, a silver halide print, or a dye coupler print, is a photographic print made from a color negative, transparency or digital image, and developed using a chromogenic process. They are composed of three layers of gelatin, each containing an emulsion of silver halide, which is used as a light-sensitive material, and a different dye coupler of subtractive color which together, when developed, form a full-color image.
Photographic developer solutions may contain more than one developing agents, such as Metol and hydroquinone, or Phenidone and hydroquinone. This is because they work together to a synergistic effect, called superadditive development.
Photographic emulsion is a light-sensitive colloid used in film-based photography. Most commonly, in silver-gelatin photography, it consists of silver halide crystals dispersed in gelatin. The emulsion is usually coated onto a substrate of glass, films, paper, or fabric. The substrate is often flexible and known as a film base.
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.
Photographic hypersensitization refers to a set of processes that can be applied to photographic film or plates before exposing. One or more of these processes is often needed to make photographic materials work better in long exposures.
In photography, solarization is the effect of tone reversal observed in cases of extreme overexposure of the photographic film in the camera. Most likely, the effect was first observed in scenery photographs including the sun. The sun, instead of being the whitest spot in the image, turned black or grey. For instance, Minor White's photograph of a winter scene, The Black Sun 1955, was a result of the shutter of his camera freezing in the open position, producing severe overexposure. Ansel Adams had also earlier created a solarized sun image, titled Black Sun, Owens Valley, California, 1939, by overexposure.
