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101-573: Silver mining activity in the Fresnillo area can be traced back to 1550. As is quite common with long-running large-scale mining operations, especially silver mining, which uses large quantities of cyanide , there have been allegations of mine-related pollution including contamination of water sources, increased illness rates amongst cattle and people, and increased air pollution. This particular mine has obtained ISO 14000 certification of its environmental management processes and equipment, and has received

202-468: A tailings pond . 23°09′43″N 102°52′23″W  /  23.162°N 102.873°W  / 23.162; -102.873 This article about a location in the Mexican state of Zacatecas is a stub . You can help Misplaced Pages by expanding it . Silver mining Silver mining is the extraction of silver by mining . Silver is a precious metal and holds high economic value. Because silver

303-425: A "Clean Industry Registration" from Mexican authorities. The mining company has also established an "ecological park", which is basically a sanctuary for over a hundred species of mammals, birds and reptiles. This park, established in 2004, was designed as a public area ( Parque los Jales ) and includes lakes, paths and open areas for physical exercise and relaxation. The park was established on land formerly occupied by

404-428: 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

505-447: 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

606-419: 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,

707-408: 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

808-410: A contaminant in chalcopyrite and galena , important ores of copper and lead , respectively. Some ores are actually mined explicitly for their silver value vs. the silver being a byproduct of other metals. However, silver is only found rarely in a native form as nuggets, in placer deposits, and veins. Methods for mining silver change for every body of ore. The method that's chosen depends on

909-424: 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

1010-435: 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

1111-465: 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

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1212-743: A handful of which are still active today. The first major silver ore deposits in the United States were discovered at the Comstock Lode in Virginia City, Nevada , in 1859. By the 1870's, silver production had increased from 40 millions ounces per year to 80 million. From 1872 to 1920, a surge of technological innovation increased global silver production to 120 million ounces produced per year. New silver deposits had been discovered in Australia, Canada, United States, Africa, Mexico, Chile, and Japan, and by

1313-521: 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

1414-462: 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

1515-571: 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

1616-440: A significant amount of mental stress on indigenous workers due to the long hours of work, rough working conditions, repetitive nature of the work, roster schedules, and potential job loss. The use of addictive substances is also an active concern amongst indigenous workers. When income increases, workers are more likely to purchase alcohol and binge drink . This leads to a variety of social and health effects such as cirrhosis of

1717-433: 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;

1818-467: 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

1919-414: A source of recycled metal compared to electronics and photographic film. The main techniques to process silver scrap: electrolysis , metallic replacement, and precipitation . Electrolytic silver recovery refers to the process where silver cations are reduced to their metallic state, adhering to an electrode. In metallic replacement, a solution of silver thiosulfate is converted to the metallic state by

2020-430: 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

2121-464: 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

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2222-870: 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

2323-455: 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

2424-705: Is a Spanish adjective meaning "silvery". Silver mining was a driving force in the settlement of western North America , with major booms for silver and associated minerals (lead, mostly) in the galena ore silver is most commonly found in. Notable silver rushes were in Colorado ; Nevada ; Cobalt, Ontario ; California and the Kootenay region of British Columbia ; notably in the Boundary and "Silvery" Slocan . A silver rush in Idaho produced mines in an area known as Silver Valley ,

2525-402: Is a technique used to extract gold and silver from lower-grade ores. Mercury quickly sticks to gold and silver and forms pasty amalgams, making extraction easier. After separating it from the ore, amalgam is roasted and mercury vapor escapes into the atmosphere and also makes its way into rivers and soils. From the years 1545 to 1803, over 25,000 tons of silver were produced using amalgamation in

2626-518: Is also produced during the electrolytic refining of copper and by application of the Parkes process on lead ores. Commercial grade fine silver is at least 99.9 percent pure silver, and purities greater than 99.999 percent are available. About 5000 tons of silver are annually recovered from scrap. Jewelry , photographic film , silverware , coins , and electronics are sources of recyclable silver. However, jewelry and silverware are not as important of

2727-543: 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

2828-481: 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

2929-403: 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,

3030-539: 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

3131-414: 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

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3232-401: 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

3333-940: 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

3434-611: Is often found in intimate combination with other metals, its extraction requires the use of complex technologies. In 2008, approximately 25,900 metric tons of silver were consumed worldwide, most of which came from mining. Silver mining has a variety of effects on the environment, humans, and animals. Silver-bearing ore typically contains very little silver, with much higher percentages of copper and lead. Specific minerals include argentite (Ag 2 S ), chlorargyrite ("horn silver," Ag Cl ), polybasite (Ag, Cu) 16 Sb 2 S 11 ), and proustite (Ag 3 AsS 3 ). Silver mainly occurs as

3535-464: 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

3636-495: 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

3737-569: 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

3838-610: 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

3939-528: 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

4040-447: 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

4141-482: 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

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4242-623: The liquation process creating a boost to the mining and metallurgy industries of Central Europe . Vast amounts of silver were brought into the possession of the crowns of Europe after the conquest of the Americas from the now Mexican state of Zacatecas (discovered in 1546) and Potosí (also discovered in 1546), which triggered the Spanish Price Revolution in Europe. Between 1500 and 1800, Bolivia , Peru , and Mexico made of 85% of

4343-717: The Americas since the patio process was first used. 60-65% of this is likely released into the atmosphere, being the single largest contributor to the global mercury cycle . In the year 2000, small-scale miners in Chile experienced many risks to their health, safety, and hygiene from toxic pollution. This was due to wastewater being released into underground waters and creating significant quantities of mercury. Contaminants are also known to enter drinking water in and around abandoned silver mines. Well water in South Morelos State, Mexico,

4444-429: 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

4545-667: The Pacific, contributing to the rise of the Spanish Empire . The rise and fall of its value affected the world market. In the first half of the 19th century Chilean mining revived due to a silver rush in the Norte Chico region, leading to an increased presence of Chileans in the Atacama desert and a shift away from an agriculture based economy. The country of Argentina was named after its silver resources by Spanish conquistadors; Argentina

4646-527: The Potosi mines. At its peak, the town had over 6,000 smelting furnaces spreading toxic Mercury. Mercury-rich tailings are also often left in mines. The amalgamation methods have proven problematic. It is estimated that 90% of the mercury consumed in the United States from 1850 to 1900 was used to extract silver and gold . An estimated 257,400 tonnes of mercury were lost to the environment in this process in

4747-419: The action of a solid reducing agent, such a steel wool . The equipment in this process is commonly referred to as "metallic recovery cartridges". Precipitation refers to the process of extracting silver from silver-rich solutions. This technique uses precipitating agents to form silver sulfide in the solution. The precipitation method is not extensively utilized due to the fact that excess sulfide can result in

4848-432: 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

4949-472: 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

5050-752: 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

5151-439: 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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5252-614: 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

5353-409: 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

5454-399: 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

5555-495: 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

5656-479: 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

5757-435: 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

5858-411: 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

5959-404: 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

6060-466: 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

6161-494: 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

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6262-443: 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

6363-412: The end of 1920, global production surged to 190 million ounces annually. The mining techniques during the 1900's had also dramatically changed. Seam-assisted drilling, mine dewatering , and improved haulage all contributed to the spike in silver production in the 1900's. By 2019, technological innovation has allowed silver production to grow to almost 800 million ounces per year. Mercury amalgamation

6464-432: 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 ,

6565-428: 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

6666-619: 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

6767-575: 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

6868-420: 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

6969-433: The grade of the ore, the steepness and shape of the terrain, its depth, host rock, transportation availability, and other economic factors. Commonly, silver ore is obtained from open pit mines , and underground drifts and shafts . Explosives are frequently used to shatter veins into manageable pieces, which are transported via mine cars and then lifted to the surface. This process can be dangerous. Once removed from

7070-415: 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

7171-564: The islands of the Aegean Sea indicate that silver was being separated from lead as early as the 4th millennium BC . By 1,200 BC, silver mining shifted into the mines of Laurion in Greece, and continued growing the surrounding empire. The silver mines at Laurion were very rich and helped provide a currency for the economy of ancient Athens , where the process involved mining the ore in underground galleries, washing and then smelting it to produce

7272-501: 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,

7373-441: The liver, brain damage , and fetal alcohol syndrome. Silver mining operations in indigenous communities lead to increased hunting pressure and a decline in traditional practices due to population growth and better hunting technologies. This affects local animal populations and cultural rituals. Employment in mines results in longer working hours, reducing time for traditional activities like hunting and fishing , which threatens

7474-408: 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

7575-414: The loss of traditional languages, attributed to factors like migration, labor market participation, and lack of educational support. 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 the crystals determine

7676-602: The metal. Elaborate washing tables still exist at the site which used rain water held in cisterns and collected during the winter months. By the year 100 AD, the epicenter of silver mining transitioned into Spain, where the Roman Empire flourished. The Romans took over silver mining in Spain from Carthage after their acquisition of Carthaginian territories there following the Second Punic War . Extraction of silver from lead ore

7777-428: The mine, silver-containing ore is crushed ( comminution ) into a fine powder to expose individual grains to chemical processing. As a byproduct of the mining of lead and copper, silver ores are often purified by froth flotation . After froth flotation, silver is extracted by a cyanide process , akin to technology used for gold extraction . In some cases, the ore is treated by smelting before cyanide treatment. Silver

7878-442: 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

7979-405: 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

8080-491: 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

8181-425: The release of toxic gas. The principal sources of silver are copper , copper- nickel , gold , lead , and lead - zinc ores obtained from Canada , Mexico , Poland , Peru , Bolivia , Australia and the United States . Mexico was the world's largest silver producer in 2014, producing 5,000 metric tons (161 million troy ounces ), 18.7 percent of the 26,800 tonnes (862 million troy ounce) production of

8282-414: 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

8383-419: 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

8484-470: 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

8585-416: 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

8686-650: 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

8787-519: 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

8888-1154: The spreading of ecological knowledge and cultural practices. While mining can provide economic resources for purchasing hunting equipment, it also accelerates the decline in traditional lifestyles and cultural heritage, impacting food security and community cohesion in indigenous populations. Mining projects also pose significant threats to family integrity, manifesting in decreased quality and quantity of family time due to long working hours and associated stressors, as well as disruptions to traditional familial roles and responsibilities. Limited time for communication and support may exacerbate existing problems within families. This leads to fragmentation and potential conflicts, with spouses having increased household responsibilities and children facing adverse consequences such as behavioral issues and academic struggles. Silver mining in indigenous communities lead to cultural shifts, with Western values often replacing traditional ones. While some argue that mining can promote cultural values such as independence and pride through job creation and increased disposable income, others highlight negative impacts such as

8989-437: 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

9090-475: 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

9191-624: The world's total silver production. Silver mining required large amounts of mercury to extract the metal from ore. In the Andes, the source was the Huancavelica mercury mine; Mexico was dependent on mercury from the Almadén mercury mine in Spain. Mercury had a high adverse environmental impact. Silver was extremely valuable in China , and became a global commodity. Manila galleons carried Spanish dollars across

9292-642: The world. Silver mining companies engage in the discovery and production of silver. While these companies prioritize in silver, many of them also engage in other metals such as gold , palladium , lead , and zinc . The historical record of silver mining dates back to 3,000 BC in Anatolia . As silver is a precious metal often used for coins and bullion, its mining has historically often been lucrative. As with other precious metals such as gold or platinum , newly discovered deposits of silver ore have sparked silver rushes of miners seeking their fortunes. Silver

9393-497: Was a valuable metal that helped early civilizations around Ancient Greece. In recent centuries, large deposits were discovered and mined in the Americas, influencing the growth and development of Mexico, Andean countries such as Bolivia, Chile and Peru, as well as Argentina, Canada and the United States. Silver is mentioned in the Book of Genesis , and slag heaps found in Asia Minor and on

9494-411: 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

9595-525: Was found to have high concentrations of toxic minerals including arsenic , iron , manganese , lead , and fluorine . This is attributed to the abandoned and flooded silver mine at Huautla. Groundwaters flooded the mine-shafts after they were abandoned in the early 1990s, which allowed for oxidation and mobilization of these dangerous contaminants. Mining has negative impacts on both humans and societies. It affects Indigenous peoples living in communities nearby silver mines in many ways. Silver mining puts

9696-438: 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

9797-448: 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

9898-481: 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

9999-464: 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

10100-420: 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

10201-671: Was widespread in Roman Britain very soon after the Roman conquest of the first century AD. One of the main aims of the Viking expansion throughout Europe was to acquire and trade silver. Bergen and Dublin are still important centres of silver making. An example of a collection of Viking-age silver for trading purposes is the Galloway Hoard . From the mid-15th century silver began to be extracted from copper ores in massive quantities using

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