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106-409: The size of the core is dependent on several factors. A smaller core will obviously allow more material to be stored in a given space. However, there is a limit to how tightly the stored material can be wound without damaging it and this limits how small the core can be. Other issues affecting the core size include: With material such as photographic film that is flat and long but is relatively wide,

212-463: A 35 mm film reel is 1,000 feet (305 m), which runs approximately 11 minutes for sound film (24 frames per second ) and about 15 minutes for silent film at the more or less standard speed of 18 frames per second. Most films have visible cues which mark the end of the reel . This allows projectionists running reel-to-reel to change over to the next reel on the other projector . A so-called "two-reeler" would have run about 15–24 minutes since

318-428: A PET (polyethylene terephthalate) plastic film base. Films with a triacetate base can suffer from vinegar syndrome , a decomposition process accelerated by warm and humid conditions, that releases acetic acid which is the characteristic component of vinegar, imparting the film a strong vinegar smell, accelerating damage within the film and possibly even damaging surrounding metal and films. Films are usually spliced using

424-447: A certain filter, assume ISO 25 under daylight and ISO 64 under tungsten lighting"). This allows a light meter to be used to estimate an exposure. The focal point for IR is slightly farther away from the camera than visible light, and UV slightly closer; this must be compensated for when focusing. Apochromatic lenses are sometimes recommended due to their improved focusing across the spectrum. Film optimized for detecting X-ray radiation

530-419: 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,

636-408: A complex development process, with multiple dyeing steps as each color layer was processed separately. 1936 also saw the launch of Agfa Color Neu, the first subtractive three-color reversal film for movie and still camera use to incorporate color dye couplers, which could be processed at the same time by a single color developer. The film had some 278 patents. The incorporation of color couplers formed

742-483: A crystalline defect (edge dislocation), and incorporating a trace amount of non-silver salt as a dopant. The location, kind and number of shallow traps have a huge influence on the efficiency by which the photoelectrons create latent image centers, and consequently, on photographic sensitivity. Another important way to increase photographic sensitivity is to reduce the threshold size of developable latent images. Gold sensitization of Koslowski creates metallic gold specks on

848-424: A faster film. A film with a particular ISO rating can be push-processed , or "pushed", to behave like a film with a higher ISO, by developing for a longer amount of time or at a higher temperature than usual. More rarely, a film can be "pulled" to behave like a "slower" film. Pushing generally coarsens grain and increases contrast, reducing dynamic range, to the detriment of overall quality. Nevertheless, it can be

954-435: A feature that was eventually adapted by all camera and film manufacturers. DX encoding provides information on both the film cassette and on the film regarding the type of film, number of exposures, speed (ISO/ASA rating) of the film. It consists of three types of identification. First is a barcode near the film opening of the cassette, identifying the manufacturer, film type and processing method ( see image below left ). This

1060-465: A few special applications as an alternative to the hazardous nitrate film, which had the advantages of being considerably tougher, slightly more transparent, and cheaper. The changeover was completed for X-ray films in 1933, but although safety film was always used for 16 mm and 8 mm home movies, nitrate film remained standard for theatrical 35 mm films until it was finally discontinued in 1951. Hurter and Driffield began pioneering work on

1166-404: A layer just under the crystal surface where a sufficient number of edge dislocations are intentionally created, while maintaining the bulk of the crystal interior defect-free. Chemical sensitization (e.g., sulfur plus gold sensitization) is applied on the surface. As a result, the photoelectrons are concentrated to a few sensitivity sites on or very near the crystal surface, thereby greatly enhancing

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1272-403: A lighter and smaller form than film would on a "fixed" reel. In the silent era , the term was used to describe a single reel that accommodated two or more individual titles. As digital cinema catches on, the physical reel is being replaced by a virtual format called Digital Cinema Package , which can be distributed using any storage medium (such as hard drives) or data transfer medium (such as

1378-528: A linear response through the effective exposure range). The sensitivity (i.e., the ISO speed) of a film can be affected by changing the length or temperature of development, which would move the H&;D curve to the left or right ( see figure ). If parts of the image are exposed heavily enough to approach the maximum density possible for a print film, then they will begin losing the ability to show tonal variations in

1484-467: A neutral one. One very important way to increase photographic sensitivity is to manipulate the electron traps in each crystal. A pure, defect-free crystal exhibits poor photographic sensitivity, since it lacks a shallow electron trap that facilitates the formation of a latent image. In such a case, many of the photoelectrons will recombine with the silver halide crystal and be wasted. Shallow electron traps are created by sulfur sensitization, introduction of

1590-462: A number of disadvantages as a scientific detector: it is difficult to calibrate for photometry , it is not re-usable, it requires careful handling (including temperature and humidity control) for best calibration, and the film must physically be returned to the laboratory and processed. Against this, photographic film can be made with a higher spatial resolution than any other type of imaging detector, and, because of its logarithmic response to light, has

1696-602: A number of ways. Each emulsion has a place within each crystal where LIs are formed preferentially. They are called "sensitivity centers." Emulsions that form LIs in the interior are called internal(ly) sensitive emulsions, and those that form LI on the surface are called surface sensitive emulsions. The sensitivity type largely reflects the site of very shallow electron traps that form latent images effectively. Most, if not all, old technology negative film emulsions had many unintentionally created edge dislocation sites (and other crystalline defects) internally and sulfur sensitization

1802-406: A photoelectron, from a silver halide crystal. Photoelectrons migrate to a shallow electron trap site (a sensitivity site), where the electrons reduce silver ions to form a metallic silver speck. A positive hole must also be generated, but it is largely ignored. Subsequent work has slightly modified this picture, so that "hole" trapping is also considered (Mitchell, 1957). Since then, understanding of

1908-571: A result, the relative tonal values in a scene registered roughly as they would appear if viewed through a piece of deep blue glass. Blue skies with interesting cloud formations photographed as a white blank. Any detail visible in masses of green foliage was due mainly to the colorless surface gloss. Bright yellows and reds appeared nearly black. Most skin tones came out unnaturally dark, and uneven or freckled complexions were exaggerated. Photographers sometimes compensated by adding in skies from separate negatives that had been exposed and processed to optimize

2014-433: A single color of light and allow all others to pass through. Because of these colored couplers, the developed film appears orange. Colored couplers mean that corrections through color filters need to be applied to the image before printing. Printing can be carried out by using an optical enlarger, or by scanning the image, correcting it using software and printing it using a digital printer. Kodachrome films have no couplers;

2120-467: A single photon striking a grain (based on the size of the grains and how closely spaced they are), and density is the proportion of grains that have been hit by at least one photon. The relationship between density and log exposure is linear for photographic films except at the extreme ranges of maximum exposure (D-max) and minimum exposure (D-min) on an H&D curve, so the curve is characteristically S-shaped (as opposed to digital camera sensors which have

2226-430: A special adhesive tape; those with PET layers can be ultrasonically spliced or their ends melted and then spliced. The emulsion layers of films are made by dissolving pure silver in nitric acid to form silver nitrate crystals, which are mixed with other chemicals to form silver halide grains, which are then suspended in gelatin and applied to the film base. The size and hence the light sensitivity of these grains determines

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2332-417: A stable latent image center, a smaller and less stable silver speck is made. Further generation of photoelectrons is necessary to grow this speck to a larger, stable, latent image. There is a finite probability that this intermediate unstable speck will decompose before next available photoelectrons can stabilize it. This probability increases with decreasing irradiance level. LIRF can be improved by optimizing

2438-464: A triangle with or without clipped edges; this type of crystal is known as a T-grain crystal or a tabular grain (T-grains). Films using T-grains are more sensitive to light without using more silver halide since they increase the surface area exposed to light by making the crystals flatter and larger in footprint instead of simply increasing their volume. T-grains can also have a hexagonal shape. These grains also have reduced sensitivity to blue light which

2544-870: A useful tradeoff in difficult shooting environments, if the alternative is no usable shot at all. Instant photography, as popularized by Polaroid , uses a special type of camera and film that automates and integrates development, without the need of further equipment or chemicals. This process is carried out immediately after exposure, as opposed to regular film, which is developed afterwards and requires additional chemicals. See instant film . Films can be made to record non- visible ultraviolet (UV) and infrared (IR) radiation. These films generally require special equipment; for example, most photographic lenses are made of glass and will therefore filter out most ultraviolet light. Instead, expensive lenses made of quartz must be used. Infrared films may be shot in standard cameras using an infrared band- or long-pass filters , although

2650-537: A very brief but intense laser. Problems due to HIRF were the major technical challenge in development of such products. Color photographic papers are usually made with very high percentage of silver chloride (about 99%) and the rest is bromide and/or iodide. Chloride emulsions have particularly poor HIRF and usually suffer from LIRF. Paper manufacturers use dopants and precise control of the dislocation sites to improve (to virtually eliminate) HIRF for this new application. Low-intensity reciprocity failure (LIRF) occurs when

2756-455: A wider dynamic range than most digital detectors. For example, Agfa 10E56 holographic film has a resolution of over 4,000 lines/mm – equivalent to a pixel size of 0.125 micrometers – and an active dynamic range of over five orders of magnitude in brightness, compared to typical scientific CCDs that might have pixels of about 10 micrometers and a dynamic range of 3–4 orders of magnitude. Special films are used for

2862-415: Is a limit in increasing the photographic speed of the system by boosting the developer potential; if the solution's reduction potential is set high enough to exploit smaller silver cluster, at some point the solution begins to reduce silver halide crystals regardless of exposure. This is called fog , which is metallic silver made from non-imagewise (exposure-nonspecific) reduction of silver halide crystals. It

2968-543: Is also similar to photographic film. There are several types of photographic film, including: In order to produce a usable image, the film needs to be exposed properly. The amount of exposure variation that a given film can tolerate, while still producing an acceptable level of quality, is called its exposure latitude . Color print film generally has greater exposure latitude than other types of film. Additionally, because print film must be printed to be viewed, after-the-fact corrections for imperfect exposure are possible during

3074-481: Is an advantage since silver halide is most sensitive to blue light than other colors of light. This was traditionally solved by the addition of a blue-blocking filter layer in the film emulsion, but T-grains have allowed this layer to be removed. Also the grains may have a "core" and "shell" where the core, made of silver iodobromide, has higher iodine content than the shell, which improves light sensitivity, these grains are known as Σ-Grains. The exact silver halide used

3180-403: Is blue light). The sensitizing dyes are absorbed at dislocations in the silver halide particles in the emulsion on the film. The sensitizing dyes may be supersensitized with a supersensitizing dye, that assists the function of the sensitizing dye and improves the efficiency of photon capture by silver halide. Each layer has a different type of color dye forming coupler: in the blue sensitive layer,

3286-438: Is called fogging developer and such a solution is used in the second developer of reversal processing.) This conversion is due to electrochemical reduction, wherein the latent image centers act as a catalyst. A developer solution must have a reduction potential that is strong enough to develop sufficiently exposed silver halide crystals having a latent image center. At the same time, developer must have reduction potential that

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3392-482: Is called printing out the image. On the other hand, the formation of a visible image by the action of photographic developer is called developing out the image. The size of a silver cluster in the latent image can be as small as a few silver atoms. However, in order to act as an effective latent image center, at least four silver atoms are necessary. On the other hand, a developed silver grain can have billions of silver atoms. Therefore, photographic developer acting on

3498-479: Is common when the crystal is exposed by intense but brief light, such as flash tube. This reduces photographic speed and contrast. This is common with emulsions optimized for highest sensitivity with long exposure using old emulsion technology. HIRF is due to creation of many latent subimages that are not developable due to small size. Because of brief and intense exposure, many photoelectrons are created simultaneously. They make many latent subimages (that cannot render

3604-543: Is commonly used for medical radiography and industrial radiography by placing the subject between the film and a source of X-rays or gamma rays, without a lens, as if a translucent object were imaged by being placed between a light source and standard film. Unlike other types of film, X-ray film has a sensitive emulsion on both sides of the carrier material. This reduces the X-ray exposure for an acceptable image – a desirable feature in medical radiography. The film

3710-414: Is done by making couplers with a ballast group such as a lipophilic group (oil-protected) and applying them in oil droplets to the film, or a hydrophilic group, or in a polymer layer such as a loadable latex layer with oil-protected couplers, in which case they are considered to be polymer-protected. The color couplers may be colorless and be chromogenic or be colored. Colored couplers are used to improve

3816-401: Is due to the statistics of grain activation: as the film becomes progressively more exposed, each incident photon is less likely to impact a still-unexposed grain, yielding the logarithmic behavior. A simple, idealized statistical model yields the equation density = 1 – ( 1 – k ) , where light is proportional to the number of photons hitting a unit area of film, k is the probability of

3922-940: Is either silver bromide or silver bromochloroiodide, or a combination of silver bromide, chloride and iodide. Silver iodobromide may be used as a silver halide. Silver halide crystals can be made in several shapes for use in photographic films. For example, AgBrCl hexagonal tabular grains can be used for color negative films, AgBr octahedral grains can be used for instant color photography films, AgBrl cubo-octahedral grains can be used for color reversal films, AgBr hexagonal tabular grains can be used for medical X-ray films, and AgBrCl cubic grains can be used for graphic arts films. In color films, each emulsion layer has silver halide crystals that are sensitized to one particular color (wavelength of light) vía sentizing dyes, to that they will be made sensitive to only one color of light, and not to others, since silver halide particles are intrinsically sensitive only to wavelengths below 450 nm (which

4028-474: Is used by photofinishing equipment during film processing. The second part is a barcode on the edge of the film ( see image below right ), used also during processing, which indicates the image film type, manufacturer, frame number and synchronizes the position of the frame. The third part of DX coding, known as the DX Camera Auto Sensing (CAS) code, consists of a series of 12 metal contacts on

4134-499: Is usually placed in close contact with phosphor screen(s) and/or thin lead-foil screen(s), the combination having a higher sensitivity to X-rays. Because film is sensitive to x-rays, its contents may be wiped by airport baggage scanners if the film has a speed higher than 800 ISO. This property is exploited in Film badge dosimeters . Film optimized for detecting X-rays and gamma rays is sometimes used for radiation dosimetry . Film has

4240-502: Is weak enough not to reduce unexposed silver halide crystals. In a suitably formulated developer, electrons are injected to the silver halide crystals only through silver speck (latent image). Therefore, it is very important for the chemical reduction potential of the developer solution (not the standard reduction potential of the developing agent) to be somewhere higher than the Fermi energy level of small metallic silver clusters (that is,

4346-580: The ASA speed and the DIN speed in the format ASA/DIN. Using ISO convention film with an ASA speed of 400 would be labeled 400/27°. A fourth naming standard is GOST , developed by the Russian standards authority. See the film speed article for a table of conversions between ASA, DIN, and GOST film speeds. Common film speeds include ISO 25, 50, 64, 100, 160, 200, 400, 800 and 1600. Consumer print films are usually in

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4452-624: The K-14 process , Kodacolor, Ektachrome , which is often processed using the E-6 process and Fujifilm Superia , which is processed using the C-41 process . The chemicals and the color dye couplers on the film may vary depending on the process used to develop the film. Film speed describes a film's threshold sensitivity to light. The international standard for rating film speed is the ISO scale, which combines both

4558-540: The Lumière Brothers introduced their Lumière Panchromatic plate, which was made sensitive, although very unequally, to all colors including red. New and improved sensitizing dyes were developed, and in 1902 the much more evenly color-sensitive Perchromo panchromatic plate was being sold by the German manufacturer Perutz . The commercial availability of highly panchromatic black-and-white emulsions also accelerated

4664-447: The infrared (IR) region of the spectrum . In black-and-white photographic film, there is usually one layer of silver halide crystals. When the exposed silver halide grains are developed, the silver halide crystals 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, incorporating different combinations of sensitizing dyes. Typically

4770-482: The light sensitivity of photographic emulsions in 1876. Their work enabled the first quantitative measure of film speed to be devised. They developed H&D curves, which are specific for each film and paper. These curves plot the photographic density against the log of the exposure, to determine sensitivity or speed of the emulsion and enabling correct exposure. Early photographic plates and films were usefully sensitive only to blue, violet and ultraviolet light . As

4876-429: The ISO 100 to ISO 800 range. Some films, like Kodak's Technical Pan , are not ISO rated and therefore careful examination of the film's properties must be made by the photographer before exposure and development. ISO 25 film is very "slow", as it requires much more exposure to produce a usable image than "fast" ISO 800 film. Films of ISO 800 and greater are thus better suited to low-light situations and action shots (where

4982-432: The active dynamic range of most films, the density of the developed film is proportional to the logarithm of the total amount of light to which the film was exposed, so the transmission coefficient of the developed film is proportional to a power of the reciprocal of the brightness of the original exposure. The plot of the density of the film image against the log of the exposure is known as an H&D curve. This effect

5088-416: The actual short film shipped to a movie theater for exhibition may have had slightly less (but rarely more) than 1,000 ft (305 m) on it. Most modern projectionists use the term "reel" when referring to a 2,000-foot (610 m) "two-reeler", as modern films are rarely shipped by single 1,000-foot (305 m) reels. A standard Hollywood movie averages about five 2,000-foot reels in length. The "reel"

5194-472: 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 ultraviolet light, X-rays , gamma rays , and high-energy particles . Unmodified silver halide crystals are sensitive only to the blue part of the visible spectrum, producing unnatural-looking renditions of some colored subjects. This problem

5300-755: The back of the film base in triacetate film bases or in the front in PET film bases, below the emulsion stack. An anticurl layer and a separate antistatic layer may be present in thin high resolution films that have the antihalation layer below the emulsion. PET film bases are often dyed, specially because PET can serve as a light pipe; black and white film bases tend to have a higher level of dying applied to them. The film base needs to be transparent but with some density, perfectly flat, insensitive to light, chemically stable, resistant to tearing and strong enough to be handled manually and by camera mechanisms and film processing equipment, while being chemically resistant to moisture and

5406-439: The back of the film, it also serves to prevent scratching, as an antistatic measure due to its conductive carbon content, and as a lubricant to help transport the film through mechanisms. The antistatic property is necessary to prevent the film from getting fogged under low humidity, and mechanisms to avoid static are present in most if not all films. If applied on the back it is removed during film processing. If applied it may be on

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5512-629: The basis of subsequent color film design, with the Agfa process initially adopted by Ferrania, Fuji and Konica and lasting until the late 70s/early 1980s in the West and 1990s in Eastern Europe. The process used dye-forming chemicals that terminated with sulfonic acid groups and had to be coated one layer at a time. It was a further innovation by Kodak, using dye-forming chemicals which terminated in 'fatty' tails which permitted multiple layers to coated at

5618-409: The blue and green sensitive layers and a yellow filter before the red sensitive layer; in this way each layer is made sensitive to only a certain color of light. The couplers need to be made resistant to diffusion (non-diffusible) so that they will not move between the layers of the film and thus cause incorrect color rendition as the couplers are specific to either cyan, magenta or yellow colors. This

5724-399: The blue-sensitive layer is on top, followed by a yellow filter layer to stop any remaining blue light from affecting the layers below. Next comes a green-and-blue sensitive layer, and a red-and-blue sensitive layer, which record the green and red images respectively. During development, the exposed silver halide crystals are converted to metallic silver, just as with black-and-white film. But in

5830-495: The chemicals used during processing without losing strength, flexibility or changing in size. The subbing layer is essentially an adhesive that allows the subsequent layers to stick to the film base. The film base was initially made of highly flammable cellulose nitrate, which was replaced by cellulose acetate films , often cellulose triacetate film (safety film), which in turn was replaced in many films (such as all print films, most duplication films and some other specialty films) by

5936-479: The color filter mosaic layer absorbed most of the light passing through. The last films of this type were discontinued in the 1950s, but Polachrome "instant" slide film, introduced in 1983, temporarily revived the technology. "Color film" in the modern sense of a subtractive color product with a multi-layered emulsion was born with the introduction of Kodachrome for home movies in 1935 and as lengths of 35 mm film for still cameras in 1936; however, it required

6042-435: The color reproduction of film. The first coupler which is used in the blue layer remains colorless to allow all light to pass through, but the coupler used in the green layer is colored yellow, and the coupler used in the red layer is light pink. Yellow was chosen to block any remaining blue light from exposing the underlying green and red layers (since yellow can be made from green and red). Each layer should only be sensitive to

6148-411: The coupler forms a yellow dye; in the green sensitive layer the coupler forms a magenta dye, and in the red sensitive layer the coupler forms a cyan dye. Color films often have an UV blocking layer. Each emulsion layer in a color film may itself have three layers: a slow, medium and fast layer, to allow the film to capture higher contrast images. The color dye couplers are inside oil droplets dispersed in

6254-399: The crystal developable), rather than one or a few latent images (that can). HIRF can be improved by incorporating dopants that create temporary deep electron traps, optimizing the degree of sulfur sensitization, introducing crystalline defects (edge dislocation). In recent years, many photographic prints are made by scanning laser exposure. Each location on a photographic paper is exposed by

6360-403: The crystal is exposed with weak light of long duration, such as in astronomical photography. LIRF is due to inefficiency of forming a latent image, and this reduces photographic speed but increases contrast. Due to low level of exposure irradiance (intensity), a single crystal may have to wait for a significant amount of time between absorbing sufficient number of photons. In the process of making

6466-446: The crystal is used to decrease the threshold size of metallic silver cluster that can render the crystal developable. For further discussion, refer to Tani 1995 and Hamilton 1988. Under normal conditions the latent image, which may be as small as a few atoms of metallic silver on each halide grain, is stable for many months. Subsequent development can then reveal a visible metallic image. A famous instance of latent-image stability are

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6572-411: The crystal surface, which by itself does not render the crystal developable. When a latent image is formed around the gold speck, the presence of gold is known to reduce the number of metallic silver atoms necessary to render the crystal developable. Another important concept in increasing photographic sensitivity is to separate photoholes away from photoelectrons and sensitivity sites. This should reduce

6678-442: The crystals determine the sensitivity, contrast, and resolution of the film. Film is typically segmented in frames , that give rise to separate photographs . 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

6784-467: The date, shutter speed and aperture setting are recorded on the negative directly as the film is exposed. The first known version of this process was patented in the United States in 1975, using half-silvered mirrors to direct the readout of a digital clock and mix it with the light rays coming through the main camera lens. Modern SLR cameras use an imprinter fixed to the back of the camera on

6890-466: The dyes are instead formed by a long sequence of steps, limiting adoption among smaller film processing companies. Black and white films are very simple by comparison, only consisting of silver halide crystals suspended in a gelatin emulsion which sits on a film base with an antihalation back. Many films contain a top supercoat layer to protect the emulsion layers from damage. Some manufacturers manufacture their films with daylight, tungsten (named after

6996-502: The early 20th century. Although color photographs of good quality were being made by the 1890s, they required special equipment, separate and long exposures through three color filters , complex printing or display procedures, and highly specialized skills, so they were then exceedingly rare. The first practical and commercially successful color "film" was the Lumière Autochrome , a glass plate product introduced in 1907. It

7102-640: The efficiency with which the latent image is produced. Emulsions with different structures were made for other applications, such as direct positive emulsions. Direct positive emulsion has fog centers built into the core of the emulsion, which is bleached by photoholes generated upon exposure. This type of emulsion produces a positive image upon development in a conventional developer, without reversal processing. A developer solution converts silver halide crystals to metallic silver grains, but it acts only on those having latent image centers. (A solution that converts all silver halide crystals to metallic silver grains

7208-443: The emulsion around silver halide crystals, forming a silver halide grain. Here the oil droplets act as a surfactant , also protecting the couplers from chemical reactions with the silver halide and from the surrounding gelatin. During development, oxidized developer diffuses into the oil droplets and combines with the dye couplers to form dye clouds; the dye clouds only form around unexposed silver halide crystals. The fixer then removes

7314-432: The film backing plate. It uses a small LED display for illumination and optics to focus the light onto a specific part of the film. The LED display is exposed on the negative at the same time the picture is taken. Digital cameras can often encode all the information in the image file itself. The Exif format is the most commonly used format. In the 1980s, Kodak developed DX Encoding (from Digital indeX), or DX coding ,

7420-428: The film cassette, which beginning with cameras manufactured after 1985 could detect the type of film, number of exposures and ISO of the film, and use that information to automatically adjust the camera settings for the speed of the film. Source: e.g., Kodak "Advantix", different aspect ratios possible, data recorded on magnetic strip, processed film remains in cartridge The earliest practical photographic process

7526-625: The film's sensitivity to light – or speed – the film there will have no appreciable image density, and will appear on the print as a featureless black. Some photographers use their knowledge of these limits to determine the optimum exposure for a photograph; for one example, see the Zone System . Most automatic cameras instead try to achieve a particular average density. Color films can have many layers. The film base can have an antihalation layer applied to it or be dyed. This layer prevents light from reflecting from within

7632-575: The film, increasing image quality. This also can make films exposable on only one side, as it prevents exposure from behind the film. This layer is bleached after development to make it clear, thus making the film transparent. The antihalation layer, besides having a black colloidal silver sol pigment for absorbing light, can also have two UV absorbents to improve lightfastness of the developed image, an oxidized developer scavenger, dyes for compensating for optical density during printing, solvents, gelatin and disodium salt of 3,5- disulfocatechol. If applied to

7738-420: The final print. Usually those areas will be considered overexposed and will appear as featureless white on the print. Some subject matter is tolerant of very heavy exposure. For example, sources of brilliant light, such as a light bulb or the sun, generally appear best as a featureless white on the print. Likewise, if part of an image receives less than the beginning threshold level of exposure, which depends upon

7844-415: The infrared focal point must be compensated for. Exposure and focusing are difficult when using UV or IR film with a camera and lens designed for visible light. The ISO standard for film speed only applies to visible light, so visual-spectrum light meters are nearly useless. Film manufacturers can supply suggested equivalent film speeds under different conditions, and recommend heavy bracketing (e.g., "with

7950-520: The internet or satellite links) and projected using a digital projector instead of a conventional movie projector . A newsreel is a short documentary film. A showreel or demo reel is a short film showcasing a person's or organization's previous work. Photographic film 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

8056-501: The laboratory, but in 1883 the first commercially dye-sensitized plates appeared on the market. These early products, described as isochromatic or orthochromatic depending on the manufacturer, made possible a more accurate rendering of colored subject matter into a black-and-white image. Because they were still disproportionately sensitive to blue, the use of a yellow filter and a consequently longer exposure time were required to take full advantage of their extended sensitivity. In 1894,

8162-515: The latent image is a chemical amplifier with a gain factor up to several billion. The development system was the most important technology that increased the photographic sensitivity in the history of photography. The action of the light on the silver halide grains within the emulsion forms sites of metallic silver in the grains. The basic mechanism by which this happens was first proposed by R. W. Gurney and N. F. Mott in 1938. The incoming photon liberates an electron , called

8268-427: The latent image) but well below the conduction band of unexposed silver halide crystals. Generally, weakly exposed crystals have smaller silver clusters. Silver clusters of smaller sizes have a higher Fermi level, and therefore more crystals are developed as the developer's reduction potential is increased. However, again, the developer potential must be well below the conduction band of silver halide crystal. Thus there

8374-408: The long exposures required by astrophotography. Lith films used in the printing industry. In particular when exposed via a ruled-glass screen or contact-screen, halftone images suitable for printing could be generated. Some film cameras have the ability to read metadata from the film canister or encode metadata on film negatives. Negative imprinting is a feature of some film cameras, in which

8480-451: The material generally is stored in successive single layers. In cases where the material is more uniform in cross-section (for example, a cable), the material may be safely wound around a reel that is wider than its width. In this case, several windings are needed to create a layer on the reel. Examples of reel usage include: It is traditional to discuss the length of theatrical motion pictures in terms of "reels". The standard length of

8586-400: The mechanism of sensitivity and latent image formation has been greatly improved. A latent image is formed when light changes the charge atoms in the molecule. Taking bromine as a halide for this example, when light hits a silver halide molecule, the halide is changed from a negative charge to a neutral one, releasing an electron that then changes the charge of the silver from a positive one to

8692-527: The nature of the invisible change in the silver halide crystals of the film's emulsion coating was unknown, so the image was said to be "latent" until the film was treated with photographic developer . In more physical terms, a latent image is a small cluster of metallic silver atoms formed in or on a silver halide crystal due to reduction of interstitial silver ions by photoelectrons (a photolytic silver cluster). If intense exposure continues, such photolytic silver clusters grow to visible sizes. This

8798-442: The physics of silver grain activation (which sets a minimum amount of light required to expose a single grain) and by the statistics of random grain activation by photons. The film requires a minimum amount of light before it begins to expose, and then responds by progressive darkening over a wide dynamic range of exposure until all of the grains are exposed, and the film achieves (after development) its maximum optical density. Over

8904-405: The printing process. The concentration of dyes or silver halide crystals remaining on the film after development is referred to as optical density , or simply density ; the optical density is proportional to the logarithm of the optical transmission coefficient of the developed film. A dark image on the negative is of higher density than a more transparent image. Most films are affected by

9010-427: The probability of recombination. Reduction sensitization is one possible implementation of this concept. The recent 2-electron sensitization technique is built on this concept. However, the scientific understanding of the behavior of photoholes is more limited than that of photoelectrons. On the other hand, a deep electron trap or a site that facilitates recombination will compete for photoelectrons and therefore reduces

9116-491: The progress of practical color photography, which requires good sensitivity to all the colors of the spectrum for the red, green and blue channels of color information to all be captured with reasonable exposure times. However, all of these were glass-based plate products. Panchromatic emulsions on a film base were not commercially available until the 1910s and did not come into general use until much later. Many photographers who did their own darkroom work preferred to go without

9222-420: The related equipment. A 16 mm "reel" is 400 feet (122 m). It runs, at sound speed, approximately the same amount of time (11–12 minutes) as a 1,000-foot (305 m) 35 mm reel. A "split reel" is a motion picture film reel in two halves that, when assembled, hold a specific length of motion picture film that has been wound on a plastic core. Using a split reel allows film to be shipped or handled in

9328-488: The same time in a single pass, reducing production time and cost that later became universally adopted along with the Kodak C-41 process. Latent image A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film . When photographic film is developed , the area that was exposed darkens and forms a visible image. In the early days of photography,

9434-414: The seeming luxury of sensitivity to red – a rare color in nature and uncommon even in human-made objects – rather than be forced to abandon the traditional red darkroom safelight and process their exposed film in complete darkness. Kodak's popular Verichrome black-and-white snapshot film, introduced in 1931, remained a red-insensitive orthochromatic product until 1956, when it

9540-504: The sensitivity. However, these manipulations are used, for example, to enhance contrast of the emulsion. Reciprocity law failure is a phenomenon where the same amount of exposure (irradiance multiplied by duration of exposure) produces different image density when the irradiance (and thus duration) is varied. There are two kinds of reciprocity failure. They are both related to poor efficiency of utilizing photoelectrons to create latent image centers. High-intensity reciprocity failure (HIRF)

9646-470: The short exposure time limits the total light received). The benefit of slower film is that it usually has finer grain and better color rendition than fast film. Professional photographers of static subjects such as portraits or landscapes usually seek these qualities, and therefore require a tripod to stabilize the camera for a longer exposure. A professional photographing subjects such as rapidly moving sports or in low-light conditions will inevitably choose

9752-416: The silver halide crystals leaving only the dye clouds: this means that developed color films may not contain silver while undeveloped films do contain silver; this also means that the fixer can start to contain silver which can then be removed through electrolysis. Color films also contain light filters to filter out certain colors as the light passes through the film: often there is a blue light filter between

9858-650: The silver is converted back to silver halide crystals in the bleach step . It is removed from the film during the process of fixing the image on the film with a solution of ammonium thiosulfate or sodium thiosulfate (hypo or fixer). 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. Silver halide photographic paper

9964-519: The speed of the film; since films contain real silver (as silver halide), faster films with larger crystals are more expensive and potentially subject to variations in the price of silver metal. Also, faster films have more grain, since the grains (crystals) are larger. Each crystal is often 0.2 to 2 microns in size; in color films, the dye clouds that form around the silver halide crystals are often 25 microns across. The crystals can be shaped as cubes, flat rectangles, tetradecadedra, or be flat and resemble

10070-461: The stability of latent subimage, optimizing sulfur sensitization, and introduction of crystalline defects (edge dislocation). Depending on the silver halide crystal, the latent image may be formed inside or outside of the crystal. Depending on where the LI is formed, the photographic properties and the response to developer vary. Current emulsion technology allows very precise manipulation of this factor in

10176-437: The tungsten filament of incandescent and halogen lamps) or fluorescent lighting in mind, recommending the use of lens filters, light meters and test shots in some situations to maintain color balance, or by recommending the division of the ISO value of the film by the distance of the subject from the camera to get an appropriate f-number value to be set in the lens. Examples of Color films are Kodachrome , often processed using

10282-475: The visibility of the clouds, by manually retouching their negatives to adjust problematic tonal values, and by heavily powdering the faces of their portrait sitters. In 1873, Hermann Wilhelm Vogel discovered that the spectral sensitivity could be extended to green and yellow light by adding very small quantities of certain dyes to the emulsion. The instability of early sensitizing dyes and their tendency to rapidly cause fogging initially confined their use to

10388-433: Was also found that, when developer solution is optimally formulated, the maximum photographic speed is rather insensitive to the choice of developing agent (James 1945), and there exists a limit for the size of silver cluster that can be developed. One way to improve this problem is the use of the gold sensitization technique of Koslowski. A small metallic gold cluster whose Fermi level is high enough to prevent development of

10494-403: Was established as a standard measurement because of considerations in printing motion picture film at a film laboratory, for shipping (especially the film case sizes) and for the size of the physical film magazine attached to the motion picture projector. If it had not been standardized (at 1,000 ft or 305 m of 35 mm film), there would have been many difficulties in the manufacture of

10600-411: Was expensive and not sensitive enough for hand-held "snapshot" use. Film-based versions were introduced in the early 1930s and the sensitivity was later improved. These were "mosaic screen" additive color products, which used a simple layer of black-and-white emulsion in combination with a layer of microscopically small color filter elements. The resulting transparencies or "slides" were very dark because

10706-438: Was of better optical quality than early transparent plastics and was, at first, less expensive. Glass plates continued to be used long after the introduction of film, and were used for astrophotography and electron micrography until the early 2000s, when they were supplanted by digital recording methods. Ilford continues to manufacture glass plates for special scientific applications. The first flexible photographic roll film

10812-468: Was performed on the surface of the crystal. Because multiple sensitivity centers are present, the emulsion had both internal and surface sensitivity. That is, photoelectrons may migrate to one of many sensitivity centers. In order to exploit the maximum sensitivity of such emulsions, it is generally considered that the developer must have some silver halide solvent action to make the internal latent image sites accessible. Many modern negative emulsions introduce

10918-448: Was replaced by Verichrome Pan. Amateur darkroom enthusiasts then had to handle the undeveloped film by the sense of touch alone. Experiments with color photography began almost as early as photography itself, but the three-color principle underlying all practical processes was not set forth until 1855, not demonstrated until 1861, and not generally accepted as "real" color photography until it had become an undeniable commercial reality in

11024-481: Was resolved with the discovery that certain dyes, called sensitizing dyes, when adsorbed onto the silver halide crystals made them respond to other colors as well. First orthochromatic (sensitive to blue and green) and finally panchromatic (sensitive to all visible colors) films were developed. Panchromatic film renders all colors in shades of gray approximately matching their subjective brightness. By similar techniques, special-purpose films can be made sensitive to

11130-464: Was sold by George Eastman in 1885, but this original "film" was actually a coating on a paper base. As part of the processing, the image-bearing layer was stripped from the paper and attached to a sheet of hardened clear gelatin. The first transparent plastic roll film followed in 1889. It was made from highly flammable cellulose nitrate film . Although cellulose acetate or " safety film " had been introduced by Kodak in 1908, at first it found only

11236-420: Was the daguerreotype ; it was introduced in 1839 and did not use film. The light-sensitive chemicals were formed on the surface of a silver-plated copper sheet. The calotype process produced paper negatives. Beginning in the 1850s, thin glass plates coated with photographic emulsion became the standard material for use in the camera. Although fragile and relatively heavy, the glass used for photographic plates

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