Photographic film is a sheet of plastic A plastic material is any of a wide range of synthetic or semi-synthetic organic amorphous solids[citation needed] used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce costs. Monomers of plastic are either natural or synthetic (polyester Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate . Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as, nitrocellulose Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton or cellulose acetate Cellulose acetate , first prepared in 1865, is the acetate ester of cellulose. Cellulose acetate is used as a film base in photography, as a component in some adhesives, and as a frame material for eyeglasses; it is also used as a synthetic fiber and in the manufacture of cigarette filters) coated with an emulsion An emulsion is a mixture of two or more immiscible (unblendable) liquids. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion tends to imply that both the dispersed and the continuous phase are liquid. In an emulsion, one containing light-sensitive silver halide A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride (AgCl), iodide (AgI), and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX. Although most silver halides involve silver atoms with salts (bonded by gelatin Gelatin is a translucent, colorless, brittle (when dry), nearly tasteless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar way are called gelatinous. Gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution Image resolution describes the detail an image holds. The term applies to digital images, film images, and other types of images. Higher resolution means more image detail of the film. When the emulsion is sufficiently exposed to light Light is electromagnetic radiation of a wavelength that is visible to the human eye . In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not (or other forms of electromagnetic radiation Electromagnetic radiation is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to such as X-rays X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma rays. In many), it forms a latent A latent image on photographic film is an invisible image produced by the exposure of the film to light. When the film is developed, the area that was exposed darkens and forms a visible image. In the early days of photography, the nature of the invisible change in the silver halide crystals of the film's emulsion coating was unknown, so the image (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing Photographic processing is the chemical means by which photographic film and 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.

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 block light and appear as the black part of the film negative.

Color film uses at least three layers. Dyes, which adsorb Adsorption is the process of attraction of atoms or molecules from an adjacent gas or liquid to an exposed solid surface. Such attraction forces align the molecules into layers ("films") onto the existent surface 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. This leaves behind only the formed color dyes, which combine to make up the colored visible image.

Newer color films, like Kodacolor II In still photography, Kodak's Kodacolor brand has been associated with various color negative films since 1942. Kodak claims that Kodacolor print film was the world's first true color negative film. The Kodacolor name has subsequently been used on several negative films, including Kodacolor-X, Kodacolor VR and Kodacolor Gold, have as many as 12 emulsion layers, with upwards of 20 different chemicals in each layer.

Due to film photography's long history of widespread use, there are now around one trillion pictures on photographic film or photographic paper Photographic paper is paper coated with light-sensitive chemicals, used for making photographic prints in the world,[1] enough to cover an area of around ten thousand square kilometres (4000 square miles), about half the size of Wales Wales ( /ˈweɪlz/ Welsh: Cymru; pronounced [ˈkəmrɨ] (help·info)) is a country that is part of the United Kingdom, bordered by England to its east, and the Atlantic Ocean and Irish Sea to its west. Wales has a population estimated at three million and is officially bilingual; Welsh and English have equal status, and bilingual signs are the.[2]

Contents

Film basics

There are two primary types of photographic film:

In order to produce a usable image, the film needs to be exposed In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specified area 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 the printing process.

The concentration of dyes or silver salts remaining on the film after development is referred to as optical density where I is the intensity of light at a specified wavelength λ that has passed through a sample and I0 is the intensity of the light before it enters the sample or incident light intensity. Absorbance measurements are often carried out in analytical chemistry, since the absorbance of a sample is proportional to the thickness of the sample and the, or simply density; the optical density is proportional to the logarithm In mathematics, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce that number. For example, the logarithm of 1000 to base 10 is 3, because 3 is the power to which ten must be raised to produce 1000: 103 = 1000, so log101000 = 3. Only positive real numbers have real number 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 the physics of silver grain activation (which sets a minimum amount of light required to expose a single grain) and by the statistics Statistics is the formal science of making effective use of numerical data relating to groups of individuals or experiments. It deals with all aspects of this, including not only the collection, analysis and interpretation of such data, but also the planning of the collection of data, in terms of the design of surveys and experiments 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 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 In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by 1⁄x or x −1, is a number which when multiplied by x yields the multiplicative identity, 1. The multiplicative inverse of a fraction a⁄b is b⁄a. For the multiplicative inverse of a real number, divide 1 by the number. For example, the reciprocal of 5 is one of the brightness of the original exposure. This is due to the statistics of grain activation: as the film becomes progressively more exposed, each incident photon In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force. The effects of this force are easily observable at both the microscopic and macroscopic level, because the 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 ) ^ light, where "light" is proportional to the number of photons hitting a unit area of film, "k" is the probability of 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 where hit by at least one photon.

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 the final print. Usually those areas will be deemed to be overexposed and will appear as featureless white on the print. Some subject matter is tolerant of very heavy exposure; brilliant light sources like a bright lightbulb, or the sun, included in the image 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 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 The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer in 1939–1940. The Zone System provides photographers with a systematic method of precisely defining the relationship between the way they visualize the photographic subject and the final results. Although. Most automatic cameras A camera is a device that records/stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images. The modern camera evolved from the camera obscura instead try to achieve a particular average density.

Film speed

Main article: Film speed Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. Relatively insensitive film, with a correspondingly lower speed index requires more exposure to light to produce the same image density as a more sensitive film, and is

Film speed describes a film's threshold sensitivity to light. The international standard for rating film speed is the ISO scale which combines both the ASA The American National Standards Institute or ANSI [citation needed] is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American speed and the DIN Deutsches Institut für Normung e.V. is the German national organization for standardization and is that country's ISO member body 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 GOST refers to a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification , a regional standards organization operating under the auspices of the Commonwealth of Independent States (CIS). All sorts of regulated standards are included, with examples ranging from charting rules for design, developed by the Russian standards authority. See the film speed Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. Relatively insensitive film, with a correspondingly lower speed index requires more exposure to light to produce the same image density as a more sensitive film, and is 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, 1600, and 3200. Consumer print films are usually in 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 In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specified area 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 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 Tripod is a word generally used to refer to a three-legged object, generally one used as a platform of some sort, and comes from the Greek tripous, meaning "three feet". A tripod provides stability along the side-to-side and up-and-down Coordinate axis of motion and provides a large amount of leverage. Tripods have the disadvantage of to stabilize the camera for a longer exposure. Photographing subjects such as rapidly moving sports or in low-light conditions, a professional will choose a faster film. Grain size refers to the size of the silver crystals in the emulsion. The smaller the crystals, the finer the detail in the photo and the slower the film.

A film with a particular ISO rating can be pushed Push processing in photography, sometimes called uprating, refers to a film developing technique that increases the effective sensitivity of the film being processed. Push processing involves developing the film for more time, possibly in combination with a higher temperature, than the manufacturer's recommendations. This technique results in to behave like a film with a higher ISO. In order to do this, the film must be developed for a longer amount of time or at a higher temperature than usual. This procedure is usually only performed by photographers who do their own development or professional-level photofinishers. More rarely, a film can be pulled to behave like a "slower" film.

History of film

See also: Nitrocellulose#Nitrate film Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton

Hurter and Driffield began pioneering work on the light sensitivity Sensitometry is the scientific study of light-sensitive materials, especially photographic film. The study has its origins in the work by Ferdinand Hurter and Vero Charles Driffield with early black-and-white emulsions. They determined how the density of silver produced varied with the amount of light received, and the method and time of of film in 1876 onwards. Their work enabled the first quantitative measure of film speed to be devised.

Early photography in the form of daguerreotypes It was developed by Louis Daguerre together with Joseph Nicéphore Niépce. Niepce had produced the first photographic image in the camera obscura using asphaltum on a copper plate sensitised with lavender oil that required very long exposures did not use film at all. Eastman Kodak Eastman Kodak Company is a multinational US corporation which produces imaging and photographic materials and equipment. Long known for its wide range of photographic film products, Kodak is re-focusing on two major markets: digital photography and digital printing developed the first flexible photographic film in 1885. This original "film" was coated on paper. The first transparent plastic film was produced in 1889. Before this, glass photographic plates Photographic plates preceded photographic film as a means of photography. A light-sensitive emulsion of silver salts was applied to a glass plate. This form of photographic material largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile films were introduced. However, photographic plates were used, which were far more expensive and cumbersome, albeit also of better quality. The first photographic film was made from highly flammable nitrocellulose Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton with camphor Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia (particularly in Borneo and Taiwan) and also of Dryobalanops aromatica, a giant of the Bornean forests. It also occurs in some other as a plasticizer (celluloid). Beginning in the 1920s, nitrate film was replaced with cellulose acetate or "safety film". This changeover was not completed until 1933 for X-ray films (where its flammability hazard was most acute) and for motion picture film until 1951.

Spectral sensitivity

Early photographic plates and films were sensitive to blue light only. Hermann Wilhelm Vogel discovered that the spectral sensitivity could be extended by dye sensitization. Orthochromatic film sensitive to the spectral range from green to blue was introduced in 1879 and was dominant until the mid-1920s, when panchromatic film sensitive to the entire visual spectrum became standard. All of these films were used to produce black-and-white images, regardless of spectral sensitivity.

Experiments with color photography were first made in 1861, but generally usable color films only became available in the 1930s. After World War II, much progress was made, and color became used for the overwhelming majority of photographs.

Effect on lens and equipment design

Photographic lenses and equipment are designed around the film to be used. The earliest lenses needed to focus blue light only. The introduction of orthochromatic film required the spectrum from green to blue to be brought to the same focus. A red window could be used to view frame numbers of rollfilm; any red light which leaked beyond the film backing would not fog the film; and red lighting could be used in darkrooms. With the introduction of panchromatic film the whole visual spectrum needed to be brought to the same focus. In all cases a color cast in the lens glass or faint colored reflections in the image were of no consequence as they would merely change the contrast a little. This was no longer acceptable with the introduction of color film. More highly corrected lenses for newer emulsions could be used with older emulsion types, but the converse was not true.

The filters used were different for the different film types.

The progression of lens design for later emulsions is of practical importance when considering the use of old lenses, still often used on large-format equipment; a lens designed for orthochromatic film may have visible defects with a color emulsion; a lens for panchromatic film will be better but not as good as later designs.

While color processing is more complex and temperature-sensitive than for monochromatic film, the great popularity of color and almost disappearance of monochrome prompted the design of monochromatic film which is processed in exactly the same way as a standard color film.

Special films

Instant photography, as popularised 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 filter, although 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 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 sensing X-ray radiation is commonly used for medical imaging by placing the subject between the film and a source of X-rays, without a lens, as if a translucent object were imaged by being placed between a light source and standard film.

Film optimized for sensing X-rays and for gamma rays is sometimes used for radiation dosimetry and personal monitoring.

Film has 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 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 micrometres—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 micrometres and a dynamic range of 3-4 orders of magnitude.

Special films are used for the long exposures required by astrophotography.

Common sizes of film

See also: Film format

Companies

* - discontinued, ** - bankruptcy, *** - retail existing stock, production limited, **** - reseller, no manufacturing plant
  • ORWO
  • Perutz*
  • Polaroid***
  • ProClick
  • Shanghai (SMPIC Photosensitive Materials Factory)
  • Solaris (Ferrania)
  • Svema*
  • Tasma*
  • Tura**

Film manufacturers commonly make film that is branded by other companies. Modern films have bar codes (DX codes) on the edge of the film which can be read by a bar code reader. This is because film is sometimes processed differently according to specifications of the film, determined by its manufacturer; the bar code is entered into the computer printer before the film is printed.

To establish the OEM, read the bar code printed on the cassette. Divide the long number by 16 and record the number before the decimal, then multiply the number after the decimal by 16, this could give you a result such as 18 and 2.

The first number is known as the PRODUCT (film manufacturer) and the second number as the MULTIPLIER (speed of the film ISO). In the previous example, 18 identifies 3M as the manufacturer and 2 means it is 200 ISO:

See also

Wikimedia Commons has media related to: Photographic film

References

  1. ^ Lyman, Peter and Hal R. Varian, "How Much Information", 2003. Retrieved from link on 6 October 2009.
  2. ^ Assuming 100 cm2 per printed photograph.
  3. ^ Haist, Grant, Modern Photographic Processing.
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be and removed. (July 2008)

Categories: Photography equipment | Photographic films | Storage media

 

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A. I guess this is a question about the meaning of the word 'density' in the context of photgraphic film. (Rather than asking the mass of a cubic centimeter of photographic film.) Briefly: Black and white negatives usually have some dark areas and some clearer areas. Film Density is a measure of the darkness or opacity of the film at a given area of the negative. The concentration of dyes or silver salts 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. More information is available at the sites in the… [cont.]
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