1.
Photographic processing
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Photographic processing or development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image into an image, makes this permanent. All processes based upon the process are similar, regardless of the film or papers manufacturer. Exceptional variations include instant films such as made by Polaroid. Kodachrome required Kodaks proprietary K-14 process, Kodachrome film production ceased in 2009, and K-14 processing is no longer available as of December 30,2010. Ilfochrome materials use the dye destruction process, all photographic processing use a series of chemical baths. Processing, especially the development stages, requires very close control of temperature, agitation, the film may be soaked in water to swell the gelatin layer, facilitating the action of the subsequent chemical treatments. The developer converts the latent image to macroscopic particles of metallic silver, a stop bath, † typically a dilute solution of acetic acid or citric acid, halts the action of the developer. A rinse with water may be substituted. The fixer makes the image permanent and light-resistant by dissolving remaining silver halide, a common fixer is hypo, specifically ammonium thiosulfate. Washing in clean water removes any remaining fixer, residual fixer can corrode the silver image, leading to discolouration, staining and fading. The washing time can be reduced and the more completely removed if a hypo clearing agent is used after the fixer. Film may be rinsed in a solution of a non-ionic wetting agent to assist uniform drying. Film is then dried in an environment, cut and placed into protective sleeves. Once the film is processed, it is referred to as a negative. The negative may now be printed, the negative is placed in an enlarger, many different techniques can be used during the enlargement process. Two examples of enlargement techniques are dodging and burning, alternatively, the negative may be scanned for digital printing or web viewing after adjustment, retouching, and/or manipulation. † In modern automatic processing machines, the bath is replaced by mechanical squeegee or pinching rollers
2.
Latent image
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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, 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. If intense exposure continues, such photolytic silver clusters grow to visible sizes and this is called printing out the image. On the other hand, the formation of an image by the action of photographic developer is called developing out the image. The size of a cluster in the latent image can be as small as a few silver atoms. However, in order to act as a latent image center. On the other hand, a developed silver grain can have billions of silver atoms, therefore, photographic developer acting on 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 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 a photoelectron, from a silver halide crystal, photoelectrons migrate to a shallow electron trap 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. Since then, understanding of the mechanism of sensitivity and latent image formation has been greatly improved, 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 a crystalline defect, 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 size of developable latent images. Gold sensitization of Koslowski creates metallic gold specks on the crystal surface, 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 this should reduce the probability of recombination. Reduction sensitization is one implementation of this concept
3.
Redox
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Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions in which atoms have their oxidation state changed, in general, the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in terms, Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom. Reduction is the gain of electrons or a decrease in state by a molecule, atom. As an example, during the combustion of wood, oxygen from the air is reduced, the reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. Redox is a portmanteau of reduction and oxidation, the word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions, ultimately, the meaning was generalized to include all processes involving loss of electrons. The word reduction originally referred to the loss in weight upon heating a metallic ore such as an oxide to extract the metal. In other words, ore was reduced to metal, antoine Lavoisier showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the atom gains electrons in this process. The meaning of reduction then became generalized to all processes involving gain of electrons. Even though reduction seems counter-intuitive when speaking of the gain of electrons, it help to think of reduction as the loss of oxygen. Since electrons are charged, it is also helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes and these words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term hydrogenation could be used instead of reduction, since hydrogen is the agent in a large number of reactions. But, unlike oxidation, which has been generalized beyond its root element, the word redox was first used in 1928. The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction
4.
Silver halide
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A silver halide is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to silver bromide, silver chloride, silver iodide. As a group, they are referred to as the silver halides. Silver halides are light-sensitive chemicals, and are used in photographic film. The gelatin is a part of the emulsion as the protective colloid of appropriate physical and chemical properties. Gelatin may also contain elements which increase the light sensitivity of the emulsion. When a silver halide crystal is exposed to light, a sensitivity speck on the surface of the crystal is turned into a speck of metallic silver. If the speck of silver contains approximately four or more atoms, areas of the emulsion receiving larger amounts of light undergo the greatest development and therefore results in the highest optical density. Silver bromide and silver chloride may be used separately or combined, depending on the sensitivity, silver fluoride is not used in photography. Silver halides are used to make corrective lenses darken when exposed to ultraviolet light. Silver halides, except for silver fluoride, are insoluble in water. Silver nitrate can be used to precipitate halides, this application is useful in analysis of halides. The three main silver halide compounds have distinctive colours that can be used to quickly identify halide ions in a solution, the silver chloride compound forms a white precipitate, silver bromide a creamy coloured precipitate and silver iodide a yellow coloured precipitate. However, close attention is necessary for other compounds in the test solution, some compounds can considerably increase or decrease the solubility of AgX. Examples of compounds that increase the solubility include, cyanide, thiocyanate, thiosulfate, thiourea, amines, ammonia, sulfite, thioether, scientists from Tel Aviv University are experimenting with silver halide optical fibers for transmitting mid-infrared light from carbon dioxide lasers. The fibers allow laser welding of human tissue, as an alternative to traditional sutures
5.
Silver
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Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, jewelry, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table, copper and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft, ductile and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm. The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper
6.
Metol
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Metol is the organic compound with the formula HSO4. It is the sulfate salt of the protonated derivative of N-methylaminophenol. This colourless salt is a photographic developer used in black & white photography. Several methods exist for the preparation of N-methylaminophenol and it arises by decarboxylation of N-4-hydroxyphenylglycine. It can be obtained by reaction of hydroquinone with methylamine, Metol is an excellent developing agent for most continuous tone developer applications, and it has been widely used in published developer formulas as well as commercial products. However, it is difficult to produce highly concentrated developer solutions using Metol, a developer containing both Metol and hydroquinone is called an MQ developer. This combination of agents provide greater developer activity since the rate of development by both together is greater than the sum of rates of developments by each agent used alone. This combination is very versatile, by varying the quantities of Metol, hydroquinone, restrainer, and adjusting the pH, therefore, Metol replaced most other developing agents except for hydroquinone, Phenidone, and derivatives of Phenidone. Notable formulas include Eastman Kodak D-76 film developer, D-72 print developer, alfred Bogisch, working for a chemical company owned by Julius Hauff, discovered in 1891 that methylated p-aminophenol has more vigorous developing action than p-aminophenol. Hauff introduced this compound as a developing agent, the exact composition of Bogisch and Hauffs early Metol is unknown, but it was most likely methylated at the ortho position of the benzene ring, rather than at the amino group. Some time later, Metol came to mean the N-methylated variety, aktien-Gesellschaft für Anilinfabrikation sold this compound under the trade name Metol, which became by far the most common name, followed by Eastman Kodaks trade name Elon. These are principally local dermatitis of the hands and forearms, there is also some evidence of sensitization dermatitis, in which repeated exposure triggers of a chronic condition that is resistant to medication
7.
Phenidone
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Phenidone is an organic compound that is primarily used as a photographic developer. It has five to ten times the power as Metol. It also has low toxicity and, unlike some other developers, Phenidone is Ilfords trademark for this material, which was first prepared in 1890. It was not until 1940 that J. D. Kendall, large scale production did not become feasible until 1951. Phenidone functions as a reducing agent and it converts to the N-phenyl-hydroxypyrazole, Phenidone can be prepared by heating phenyl hydrazine with 3-chloropropanoic acid
8.
Hydroquinone
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Hydroquinone, also benzene-1, 4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H42. Its chemical structure, shown in the table at right, features two hydroxyl groups bonded to a ring in a para position. It is a granular solid. Substituted derivatives of this parent compound are also referred to as hydroquinones, the name hydroquinone was coined by Friedrich Wöhler in 1843. Hydroquinone is produced industrially by two main routes, the most widely used route is similar to the cumene process in reaction mechanism and involves the dialkylation of benzene with propene to give 1, 4-diisopropylbenzene. This compound reacts with air to afford the bis, which is similar to cumene hydroperoxide. A second route involves hydroxylation of phenol, the process is conducted batchwise and generates a substantial waste stream. Rhodium or ruthenium can substitute for iron as the catalyst with favorable chemical yields but are not typically used due to their cost of recovery from the reaction mixture, Hydroquinone and its derivatives can also be prepared by oxidation of various phenols. Examples include Elbs persulfate oxidation and Dakin oxidation, Hydroquinone was first obtained in 1820 by the French chemists Pelletier, the reactivity of hydroquinones O-H groups resembles other phenols, being weakly acidic. The resulting conjugate base undergoes easy O-alkylation to give mono- and diethers, similarly, hydroquinone is highly susceptible to ring substitution by Friedel-Crafts reactions such as alkylation. This reaction is exploited en route to popular antioxidants such as 2-tert-butyl-4-methoxyphenol, the useful dye quinizarin is produced by diacylation of hydroquinone with phthalic anhydride Hydroquinone undergoes oxidation under mild conditions to give benzoquinone. Some naturally occurring hydroquinone derivatives exhibit this sort of reactivity, one example being coenzyme Q, industrially this reaction is exploited both with hydroquinone itself but more often with its derivatives where one OH has been replaced by an amine. An important reaction is the conversion of hydroquinone to the mono- and it is a major component in most black and white photographic developers for film and paper where, with the compound metol, it reduces silver halides to elemental silver. There are various other associated with its reducing power. As a polymerization inhibitor, hydroquinone prevents polymerization of acrylic acid, methyl methacrylate, cyanoacrylate and this application exploits the antioxidant properties of hydroquinone. Hydroquinone can undergo oxidation to convert to the compound parabenzoquinone, C6H4O2. Reduction of quinone reverses this reaction back to hydroquinone, some biochemical compounds in nature have this sort of hydroquinone or quinone section in their structures, such as Coenzyme Q, and can undergo similar redox interconversions. Hydroquinone can lose an H+ from both to form a diphenolate ion, the disodium diphenolate salt of hydroquinone is used as an alternating comonomer unit in the production of the polymer PEEK
9.
Sodium carbonate
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Sodium carbonate, Na2CO3, is the water-soluble sodium salt of carbonic acid. It most commonly occurs as a crystalline decahydrate, which readily effloresces to form a white powder, pure sodium carbonate is a white, odorless powder that is hygroscopic. It has a strongly alkaline taste, and forms a basic solution in water. Sodium carbonate is known domestically for its everyday use as a water softener. Historically it was extracted from the ashes of plants growing in soils, such as vegetation from the Middle East, kelp from Scotland. Because the ashes of these plants were noticeably different from ashes of timber. It is synthetically produced in quantities from salt and limestone by a method known as the Solvay process. The manufacture of glass is one of the most important uses of sodium carbonate, Sodium carbonate acts as a flux for silica, lowering the melting point of the mixture to something achievable without special materials. This soda glass is mildly water-soluble, so some calcium carbonate is added to the mixture to make the glass produced insoluble. This type of glass is known as soda lime glass, soda for the sodium carbonate, soda lime glass has been the most common form of glass for centuries. Sodium carbonate is used as a relatively strong base in various settings. For example, it is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of film developing agents. It acts as an alkali because when dissolved in water, it dissociates into the acid, carbonic acid. This gives sodium carbonate in solution the ability to attack such as aluminium with the release of hydrogen gas. It is an additive in swimming pools used to raise the ph which can be lowered by chlorine tablets. In cooking, it is used in place of sodium hydroxide for lyeing, especially with German pretzels. These dishes are treated with a solution of a substance to change the pH of the surface of the food. In chemistry, it is used as an electrolyte
10.
Borax
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Soid Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. Powdered borax is white, consisting of colorless crystals that dissolve easily in water. Borax has a variety of uses. It is a component of many detergents, cosmetics, and enamel glazes, in artisanal gold mining, the borax method is sometimes used as a substitute for toxic mercury in the gold extraction process. Borax was reportedly used by miners in parts of the Philippines in the 1900s. The term borax is used for a number of closely related minerals or chemical compounds that differ in their water content. Commercially sold borax is partially dehydrated, Borax was first discovered in dry lake beds in Tibet and was imported via the Silk Road to the Arabian Peninsula in the 8th Century AD. However, it is formulated as Na2·8H2O, since borax contains the 2− ion. In this structure, there are two four-coordinate boron atoms and two boron atoms. Borax is also converted to boric acid and other borates. When borax is added to a flame, it produces a green color. Borax is not used for purpose in fireworks due to the overwhelming yellow color of sodium. Boric acid is used to color methanol flames a transparent green, the English word borax is Latinized, the Middle English form was boras, from Old French boras, bourras. That may have been from medieval Latin baurach, borac, borax, or maybe directly from the Arabic, along with Spanish borrax and Italian borrace, the Arabic was بورق bauraq/bwrk, a word also used for borax. Traditional Arabic dictionaries say that it derives from the verb to glisten, which is also written بورق bwrq, but it seems to actually derive from the Persian būrah. The word borax is found in Arabic būraq, meaning white, which is from Middle Persian bwrk, another name for borax is tincal, from Sanskrit. The word tincal /ˈtɪŋkəl/ tinkle, or tincar /ˈtɪŋkər/ tinker, refers to crude borax, before it is purified, as mined from deposits in Tibet, Persia. The word was adopted in the 17th century from Malay tingkal and from Urdu/Persian/Arabic تنکار tinkār/tankār and these all appear to be related to the Sanskrit टांकण ṭānkaṇa
11.
PH
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In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the concentration, measured in units of moles per liter. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, at pH7, being neither an acid nor a base, contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement, the pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator. In the first papers, the notation had the H as a subscript to the p, as so. The exact meaning of the p in pH is disputed, but according to the Carlsberg Foundation and it has also been suggested that the p stands for the German Potenz, others refer to French puissance. Another suggestion is that the p stands for the Latin terms pondus hydrogenii, potentia hydrogenii and it is also suggested that Sørensen used the letters p and q simply to label the test solution and the reference solution. Currently in chemistry, the p stands for decimal cologarithm of, PH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution. P H = − log 10 = log 10 For example and this definition was adopted because ion-selective electrodes, which are used to measure pH, respond to activity. For H+ number of electrons transferred is one and it follows that electrode potential is proportional to pH when pH is defined in terms of activity. The reference electrode may be a silver chloride electrode or a calomel electrode, the hydrogen-ion selective electrode is a standard hydrogen electrode. Reference electrode | concentrated solution of KCl || test solution | H2 | Pt Firstly, the cell is filled with a solution of hydrogen ion activity. Then the emf, EX, of the cell containing the solution of unknown pH is measured. PH = pH + E S − E X z The difference between the two measured emf values is proportional to pH and this method of calibration avoids the need to know the standard electrode potential. The proportionality constant, 1/z is ideally equal to 12.303 R T / F the Nernstian slope, to apply this process in practice, a glass electrode is used rather than the cumbersome hydrogen electrode. A combined glass electrode has a reference electrode. It is calibrated against buffer solutions of hydrogen ion activity
12.
Sodium sulfite
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Sodium sulfite is a soluble sodium salt of sulfurous acid with the chemical formula Na2SO3. It is a product of sulfur dioxide scrubbing, a part of the flue-gas desulfurization process, the initial combination generates sodium bisulfite, which is converted to the sulfite by reaction with sodium hydroxide or sodium carbonate. The overall reaction is, SO2 + Na2CO3 → Na2SO3 + CO2 Sodium sulfite is used in the pulp. It is used in the purification of TNT for military use and it is used in chemical manufacturing as a sulfonation and sulfomethylation agent. It is used in the production of sodium thiosulfate and it is used in other applications, including froth flotation of ores, oil recovery, food preservatives, and making dyes. Sodium sulfite forms an adduct with aldehydes, and with ketones forms a sulfonic acid. It is used to purify or isolate aldehydes and ketones, Sodium sulfite is decomposed by even weak acids, giving up sulfur dioxide gas. Na2SO3 +2 H+ →2 Na+ + H2O + SO2 A saturated aqueous solution has pH of ~9, solutions exposed to air are eventually oxidized to sodium sulfate. If sodium sulfite is allowed to crystallize from solution at room temperature or below. The heptahydrate crystals effloresce in dry air. Heptahydrate crystals also oxidize in air to form the sulfate, the anhydrous form is much more stable against oxidation by air
13.
Oxygen
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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
14.
Potassium bromide
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Potassium bromide is a salt, widely used as an anticonvulsant and a sedative in the late 19th and early 20th centuries, with over-the-counter use extending to 1975 in the US. Its action is due to the bromide ion, potassium bromide is used as a veterinary drug, as an antiepileptic medication for dogs. Under standard conditions, potassium bromide is a crystalline powder. It is freely soluble in water, it is not soluble in acetonitrile, in a dilute aqueous solution, potassium bromide tastes sweet, at higher concentrations it tastes bitter, and tastes salty when the concentration is even higher. These effects are due to the properties of the potassium ion—sodium bromide tastes salty at any concentration. In high concentration, potassium bromide strongly irritates the mucous membrane, causing nausea. Potassium bromide, an ionic salt, is fully dissociated. It serves as a source of bromide ions, bromide can be regarded as the first effective medication for epilepsy. At the time, it was thought that epilepsy was caused by masturbation. Locock noted that bromide calmed sexual excitement and thought this was responsible for his success in treating seizures, there was not a better epilepsy drug until phenobarbital in 1912. Bromides exceedingly long life in the body made it difficult to dose without side effects. Medical use of bromides in the US was discontinued at this time, as many better, use of bromide in cats is limited because it carries a substantial risk of causing lung inflammation in them. Potassium bromide is not approved by the US Food and Drug Administration for use in humans to control seizures, in Germany, it is still approved as an antiepileptic drug for humans, particularly children and adolescents. These indications include severe forms of generalized tonic-clonic seizures, early-childhood-related Grand-Mal-seizures, adults who have reacted positively to the drug during childhood/adolescence may continue treatment. Potassium bromide tablets are sold under the brand name Dibro-Be mono, the drug has almost complete bioavailability, but the bromide ion has a relatively long half life of 12 days in the blood, making bromide salts difficult to adjust and dose. The therapeutic index for bromide is small, as with other antiepileptics, sometimes even therapeutic doses may give rise to intoxication. Often indistinguishable from expected side-effects, these include, Bromism These are central nervous system reactions, rarely, tongue disorder, aphten, bad breath, and obstipation occur. Potassium bromide is transparent from the ultraviolet to long-wave infrared wavelengths and has no significant optical absorption lines in its high transmission region
15.
Glycin
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Glycin, or N-glycine, is N-substituted p-aminophenol. It is a developing agent used in classic black-and-white developer solutions. It is unrelated to the amino acid glycine, when fresh, it is typically characterized as thin plates of white or silvery powder, turning brown with age. It is sparingly soluble in water and most organic solvents, it is soluble in alkalies. Glycin is related to 4-aminophenol and Metol, compared to Metol, glycin has a carboxyl group attached to the methyl group of the Metol. This weakens the reduction potential of the compound, and the two developers have markedly different character, glycin is slower-acting, but much longer-lasting in solution. Glycin is rarely used as a developing agent today, primarily because it is expensive, in its dry form, it also has limited shelf life compared to Metol and Phenidone. Glycin can be synthesized by reacting p-aminophenol with chloracetic acid in a solvent, other uses of glycin can be found in some procedures of analytical chemistry
16.
Pyrogallol
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Pyrogallol is an organic compound with the formula C6H33. It is a white solid although samples are typically brownish because of its sensitivity toward oxygen and it is one of three isomeric benzenetriols. It is produced in the manner it was first prepared by Scheele, presently gallic acid is obtained from tannin. Heating induces decarboxylation, Because tannin is expensive, many routes have been devised. An alternate preparation involves treating para-chlorophenoldisulphonic acid with potassium hydroxide, a variant on the route to phenols from sulfonic acids. The aquatic plant Myriophyllum spicatum produces pyrogallic acid, when in alkaline solution, it absorbs oxygen from the air, turning brown from a colourless solution. It can be used in this way to calculate the amount of oxygen in air, one can find its uses in hair dying, dying of suturing materials and for oxygen absorption in gas analysis. Pyrogallol was also used as an agent in black-and-white developers. In those days it had a reputation for erratic and unreliable behavior and it experienced a revival starting in the 1980s due largely to the efforts of experimenters Gordon Hutchings and John Wimberley. Hutchings spent over a decade working on formulas, eventually producing one he named PMK. From 1969 to 1977, Wimberley experimented with the Pyrogallol developing agent and he published his formula for WD2D in 1977 in Petersons Photographic. PMK and other modern pyro formulations are now used by many black-and-white photographers, the Film Developing Cookbook has examples. Pyrogallol use, e. g. in hair dye formulations, is declining because of concerns about its toxicity
17.
Catechol
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Catechol, also known as pyrocatechol or 1, 2-dihydroxybenzene, is an organic compound with the molecular formula C6H42. It is the isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amounts and it was first discovered by destructive distillation of the plant extract catechin. About 20 million kg are now produced annually as a commodity organic chemical, mainly as a precursor to pesticides, flavors. Catechol occurs as white crystals that are very rapidly soluble in water. Upon heating catechin above its point, a substance that Reinsch first named Brenz-Katechusäure sublimated as a white efflorescence. This was a thermal decomposition product of the flavanols in catechin, in 1841, both Wackenroder and Zwenger independently rediscovered catechol, in reporting on their findings, Philosophical Magazine coined the name pyrocatechin. In 1879, the Journal of the Chemical Society recommended that catechol be called catechol, Catechol has since been shown to occur in free-form naturally in kino and in beechwood tar. Its sulfonic acid has been detected in the urine of horses, Catechol is produced industrially by the hydroxylation of phenol using hydrogen peroxide. Its methyl ether derivative, guaiacol, converts to catechol via hydrolysis of the CH3-O bond as promoted by hydriodic acid, like other difunctional benzene derivatives, catechol readily condenses to form heterocyclic compounds. Catechol is the acid of a chelating agent used widely in coordination chemistry. Basic solutions of catechol react with iron to give the red 3−, ferric chloride gives a green coloration with the aqueous solution, while the alkaline solution rapidly changes to a green and finally to a black color on exposure to the air. Iron-containing dioxygenase enzymes catalyze the cleavage of catechol, Catechol is produced by a reversible two-electron, two-proton reduction of 1, 2-benzoquinone. The redox series catecholate dianion, monoanionic semiquinonate, and benzoquinone are collectively called dioxolenes, small amounts of catechol occur naturally in fruits and vegetables, along with the enzyme polyphenol oxidase. Upon mixing the enzyme with the substrate and exposure to oxygen, the enzyme is inactivated by adding an acid, such as lemon juice. Excluding oxygen also prevents the browning reaction, however, the activity of the enzyme increases in cooler temperatures. Benzoquinone is said to be antimicrobial, which slows the spoilage of wounded fruits and it is one of the main natural phenols in argan oil. Pyrocatechol is also found in Agaricus bisporus and it is also a component of castoreum, a substance from the castor gland of beavers, used in perfumery
18.
Iron(II) oxalate
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Ferrous oxalate, or iron oxalate, is a inorganic compound with the formula FeC2O4x where x is typically 2. These are orange compounds, poorly soluble in water, the dihydrate FeC2O42 is a coordination polymer, consisting of chains of oxalate-bridged ferrous centers, each with two aquo ligands. When heated, it dehydrates and decomposes into a mixture of oxides and pyrophoric iron metal, with release of carbon dioxide, carbon monoxide. A number of other iron oxalates are known Iron oxalate Potassium ferrioxalate Sodium ferrioxalate
19.
Iron(II) lactate
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Ferrous lactate, or iron lactate, is a chemical compound consisting of one atom of iron and two lactate anions. It has the chemical formula Fe2 and it is used as a food additive with E number E585. It is an acidity regulator and colour retention agent, and is used to fortify foods with iron. It is toxic and may cause irritation, remove all contamination, rinse with plenty of water. May cause some health symptoms including nausea after ingestion both acute and delayed
20.
Phenazone
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Phenazone is an analgesic, a non-steroidal anti-inflammatory drug and an antipyretic. It was first synthesized by Ludwig Knorr in 1887 and it crystallizes in needles which melt at 156 °C. Potassium permanganate oxidizes it to pyridazine tetracarboxylic acid, phenazone has an elimination half life of about 12 hours. Indication, Used to relieve pain and fever, antipyrine is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver. Possible adverse effects include, Allergy to pyrazolones Nausea Agranulocytosis Hepatotoxicity Propyphenazone A/B Otic Drops, ear drops combined with benzocaine to relieve pain and remove cerumen
21.
Acetanilide
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Acetanilide is an odourless solid chemical of leaf or flake-like appearance. It is also known as N-phenylacetamide, acetanil, or acetanilid, acetanilide is slightly soluble in water, and stable under most conditions. Pure crystals are plate shaped and colorless to white, acetanilide is used as an inhibitor of hydrogen peroxide decomposition and is used to stabilize cellulose ester varnishes. It has also found uses in the intermediation in rubber accelerator synthesis, dyes and dye intermediate synthesis, acetanilide is used for the production of 4-acetamidobenzenesulfonyl chloride, a key intermediate for the manufacture of the sulfa drugs. It is also a precursor in the synthesis of penicillin and other pharmaceuticals, in the 19th century acetanilide was one of a large number of compounds used as experimental photographic developers. The observed methemoglobinemia after acetanilide administration was ascribed to the proportion of acetanilide that is hydrolyzed to aniline in the body. Acetanilide is no used as a drug in its own right
22.
Amidol
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Amidol is a colorless crystalline compound with the molecular structure C6H32OH. It is a chloride salt and is used as a photographic developer. It was introduced as a agent for photographic papers in 1892. It is unusual amongst developing agents as it works most effectively in slightly acid conditions rather than the strongly alkaline conditions required for most other developers, as amidol ages it changes color to a dark red-brown. Developing dishes and equipment used to prepare amidol solutions are also frequently stained brown, prints developed in amidol are typically a very warm brown-black colour, but overdevelopment can quickly lead to chemical fogging. Amidols color change upon oxidation is used to advantage as a convenient colorimetric method for measuring the oxygen concentration in water supplies, rivers
23.
Sensitometry
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Sensitometry is the scientific study of light-sensitive materials, especially photographic film. The study has its origins in the work by Ferdinand Hurter and they determined how the density of silver produced varied with the amount of light received, and the method and time of development. Plots of film density versus the log of exposure are called curves, Hurter–Driffield curves, H–D curves, HD curves, H & D curves, D–logE curves. At moderate exposures, the shape is typically a bit like an S slanted so that its base. There is usually a central region of the HD curve which approximates to a line, called the linear or straight-line portion. The low end is called the toe, and at the top, at extremely high exposures, the density may come back down, an effect known as solarisation. Different commercial film materials cover a range from about 0.5 to about 5. Often it is not the film that one views but a second or later generation. In these cases the end-to-end gamma is approximately the product of the separate gammas, photographic paper prints have end-to-end gammas generally somewhat over 1. Projection transparencies for dark surround viewing have end-to-end gamma approximately 1.5, a full set of HD curves for a film shows how these vary with developer type and time. Driffield, being a reprint of their papers, together with a history of their early work
24.
P-Phenylenediamine
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P-Phenylenediamine is an organic compound with the formula C6H42. This derivative of aniline is a solid, but samples can darken due to air oxidation. It is mainly used as a component of engineering polymers and composites and it is also an ingredient in hair dyes and is occasionally used as a substitute for henna. PPD is produced via three routes, hydrogenation of the latter affords PPD. PPD is a precursor to plastics and fibers such as Kevlar. These applications exploit PPDs difunctionality, i. e. the presence of two amines which allow the molecules to be strung together and this polymer arises from the reaction of PPD and terephthaloyl chloride. The reaction of PPD with phosgene gives the diisocyanate, a precursor to urethane polymers and this compound is a common hair dye. Its use is being supplanted by other aniline analogues and derivatives such as 2, 5-diamino(hydroxyethylbenzene and 2, other popular derivatives include tetraaminopyrimidine and indoanilines and indophenols. Derivatives of diaminopyrazole give red and violet colours, in these applications, the nearly colourless dye precursor oxidizes to the dye. PPD is easily oxidized, and for this reason derivatives of PPD are used as antiozonants in production of rubber products, the substituents, naphthyl, isopropyl etc. affect the effectiveness of their antioxidant roles as well as their properties as skin irritants. PPD is also used as a Henna surrogate for temporary tattoos and its usage can lead to severe contact dermatitis. PPD is also used as a stain for lipids such as myelin. PPD is used by Lichenologists in the PD test to aid identification of Lichens, the aquatic LD50 of PPD is 0.028 mg/L. A formal meta-analysis was not possible due to the heterogeneity of the exposure assessment across the studies, in 2005–06, it was the tenth-most-prevalent allergen in patch tests. The CDC lists PPD as being a contact allergen, exposure routes are through inhalation, skin absorption, ingestion, and skin and/or eye contact, symptoms of exposure include throat irritation, bronchial asthma, and sensitization dermatitis. It was voted Allergen of the Year in 2006 by the American Contact Dermatitis Society, poisoning by PPD is rare in western countries
25.
Fahrenheit
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Fahrenheit is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit, after whom the scale is named. It uses the degree Fahrenheit as the unit, several accounts of how he originally defined his scale exist. The lower defining point,0 °F, was established as the temperature of a solution of brine made from parts of ice. Further limits were established as the point of ice and his best estimate of the average human body temperature. All other countries in the world now use the Celsius scale, defined since 1954 by absolute zero being −273.15 °C, on the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point is 212 °F. This puts the boiling and freezing points of water exactly 180 degrees apart, therefore, a degree on the Fahrenheit scale is 1⁄180 of the interval between the freezing point and the boiling point. On the Celsius scale, the freezing and boiling points of water are 100 degrees apart, a temperature interval of 1 °F is equal to an interval of 5⁄9 degrees Celsius. The Fahrenheit and Celsius scales intersect at −40°, absolute zero is −273.15 °C or −459.67 °F. For an exact conversion, the formulas can be applied. Again, f is the value in Fahrenheit and c the value in Celsius, f °Fahrenheit to c °Celsius, C °Celsius to f °Fahrenheit, −40 = f. Fahrenheit proposed his temperature scale in 1724, basing it on two points of temperature. In his initial scale, the point is determined by placing the thermometer in a mixture of ice, water. This is a mixture which stabilizes its temperature automatically, that stable temperature was defined as 0 °F. The second point,96 degrees, was approximately the human bodys temperature, in any case, the definition of the Fahrenheit scale has changed since. According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømers scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale. Fahrenheit observed that water boils at about 212 degrees using this scale, under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that human body temperature is approximately 98° on the revised scale
26.
Celsius
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Celsius, also known as centigrade, is a metric scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world and it is named after the Swedish astronomer Anders Celsius, who developed a similar temperature scale. The degree Celsius can refer to a temperature on the Celsius scale as well as a unit to indicate a temperature interval. Before being renamed to honour Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. The scale is based on 0° for the point of water. This scale is widely taught in schools today, by international agreement the unit degree Celsius and the Celsius scale are currently defined by two different temperatures, absolute zero, and the triple point of VSMOW. This definition also precisely relates the Celsius scale to the Kelvin scale, absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the point of water is defined as precisely 273.16 K at 611.657 pascals pressure. This definition fixes the magnitude of both the degree Celsius and the kelvin as precisely 1 part in 273.16 of the difference between absolute zero and the point of water. Thus, it sets the magnitude of one degree Celsius and that of one kelvin as exactly the same, additionally, it establishes the difference between the two scales null points as being precisely 273.15 degrees. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the point of ice is essentially unaffected by pressure. He also determined with precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the point of his temperature scale, being the boiling point. This pressure is known as one standard atmosphere, the BIPMs 10th General Conference on Weights and Measures later defined one standard atmosphere to equal precisely 1013250dynes per square centimetre. On 19 May 1743 he published the design of a mercury thermometer, in 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus reversed Celsiuss scale. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden, since the 19th century, the scientific and thermometry communities worldwide referred to this scale as the centigrade scale. Temperatures on the scale were often reported simply as degrees or. More properly, what was defined as centigrade then would now be hectograde.2 gradians, for scientific use, Celsius is the term usually used, with centigrade otherwise continuing to be in common but decreasing use, especially in informal contexts in English-speaking countries
27.
Gamma correction
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Gamma correction, or often simply gamma, is the name of a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. In the common case of A =1, inputs and outputs are typically in the range 0–1, Gamma encoding of floating-point images is not required, because the floating-point format already provides a piecewise linear approximation of a logarithmic curve. Although gamma encoding was developed originally to compensate for the characteristic of cathode ray tube displays. In CRT displays, the intensity varies nonlinearly with the electron-gun voltage. Altering the input signal by gamma compression can cancel this nonlinearity, the similarity of CRT physics to the inverse of gamma encoding needed for video transmission was a combination of luck and engineering, which simplified the electronics in early television sets. The concept of gamma can be applied to any nonlinear relationship, for a power-law curve, this slope is constant, but the idea can be extended to any type of curve, in which case gamma is defined as the slope of the curve in any particular region. For a given film formulation and processing method, this curve is its characteristic or Hurter–Driffield curve, since both axes use logarithmic units, the slope of the linear section of the curve is called the gamma of the film. Negative film typically has a less than 1, positive film typically has a gamma greater than 1. Photographic film has a greater ability to record fine differences in shade than can be reproduced on photographic paper. Similarly, most video screens are not capable of displaying the range of brightnesses that can be captured by typical electronic cameras, for this reason, considerable artistic effort is invested in choosing the reduced form in which the original image should be presented. The gamma correction, or contrast selection, is part of the repertoire used to adjust the reproduced image. Analogously, digital cameras record light using electronic sensors that usually respond linearly, in the process of rendering linear raw data to conventional RGB data, color space transformations and rendering transformations will be performed. In most computer systems, images are encoded with a gamma of about 0.45. A notable exception, until the release of Mac OS X10.6 in September 2009, were Macintosh computers, in any case, binary data in still image files are explicitly encoded, as are motion picture files. The system can optionally further manage both cases, through management, if a better match to the output device gamma is required. Below a compressed value of 0.04045 or a linear intensity of 0.00313, the dashed black curve behind the red curve is a standard γ =2.2 power-law curve, for comparison. For television signals, the actual values are defined by the video standards. A gamma characteristic is a relationship that approximates the relationship between the encoded luma in a television system and the actual desired image luminance
28.
K-14 process
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K-14 was the developing process for Kodaks Kodachrome transparency film, the last version having been designated Process K-14M. The process differed significantly from its contemporary, the E-6 process, Kodachrome film has no integral color couplers, dyes are produced during processing by the reaction of the color couplers with the oxidised developer. Due to declining sales, Kodak discontinued production of all K-14 chemistry in 2009, Dwaynes Photo, which operated the last K-14 line in the world, discontinued sales on December 30,2010, the last roll was processed on January 18,2011. The layers in the film are, top-to-bottom, blue sensitive, yellow filter, blue-green sensitive, blue-red sensitive, acetate base, the processing cycle is as follows, Backing removal, An alkaline bath softens the cellulose acetate phthalate binder. A spray wash and buffer removes the rem-jet anti-halation backing, first Developer, All exposed silver halide crystals are developed to metallic silver via a PQ developer. Cyan developer, The solution contains a color developer and a cyan coupler, after the color developer develops the silver, the oxidized developer reacts with the cyan coupler to form cyan dye. The dye is much less soluble than either the developer or the coupler so it stays in the red layer of the film, Wash Blue light re-exposure from the top, This makes the remaining undeveloped grains in the blue sensitive layer developable. The now opaque yellow filter layers prevents the light from exposing the magenta layer. It is important to avoid stray printing light exposing the film base of film, yellow developer, Analogous to the cyan developer. Wash Magenta developer, This contains a chemical fogging agent that makes all of the remaining undeveloped silver developable, if everything has worked correctly, nearly all of this silver is in the magenta layers. The developer and magenta coupler work just like the cyan and yellow developers to produce magenta dye that is insoluble, Wash Conditioner, Prepares the metallic silver for the bleach step. Bleach, Oxidises the metallic silver to silver halide, the former ferricyanide bleach did not require aeration and did not require a conditioner. Fix, Converts the silver halide to soluble compounds which are dissolved and washed from the film Wash. Rinse, Contains a wetting agent to reduce water spots, dry The result is three different color records each with the appropriate dye, just like other color films. The original Kodachrome process in 1935 used dye bleaches and was a far more complex process, although the formulae have changed over the years, the basic process steps have followed a similar pattern since the introduction of selective re-exposure Kodachrome in 1938. Kodak, Processing Kodachrome film Dwaynes Photo Kodachrome processing K-14 Process Demonstration Kodak Retires KODACHROME Film
29.
Kodachrome
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Kodachrome is a brand name for a non-substantive, color reversal film introduced by Eastman Kodak in 1935. It was one of the first successful color materials and was used for both cinematography and still photography, because of its complex processing requirements, the film was sold process-paid in the United States until 1954 when a legal ruling prohibited this. For many years it was used for color photography, especially for images intended for publication in print media. After announcing the return of Ektachrome at the beginning of 2017, Kodachrome was the first color film that used a subtractive color method to be successfully mass-marketed. Previous materials, such as Autochrome and Dufaycolor, had used the additive screenplate methods, until its discontinuation, Kodachrome was the oldest surviving brand of color film. Kodachrome is appreciated in the archival and professional market for its dark-storage longevity, because of these qualities, it was used by professional photographers such as Steve McCurry, Peter Guttman and Alex Webb. McCurry used Kodachrome for his 1984 portrait of Sharbat Gula, the Afghan Girl and it was used by Walton Sound and Film Services in the UK in 1953 for the official 16 mm film of the coronation of Elizabeth II of the United Kingdom. Copies of the film for sale to the public were also produced using Kodachrome and these had several disadvantages because they used a réseau filter made from discrete color elements that were visible upon enlargement. The finished transparencies absorbed between 70% and 80% of light projection, requiring very bright projection lamps, especially for large projections. Using the subtractive method, these disadvantages could be avoided, the first Kodak product called Kodachrome was invented by John Capstaff in 1913. His Kodachrome was a process that used only two colors, blue-green and red-orange. It required two glass plate negatives, one using a panchromatic emulsion and a red filter, the other made using an emulsion insensitive to red light. The two plates could be exposed as a bipack, which eliminated the need for multiple exposures or a color camera. After development, the images were bleached out with chemistry that hardened the bleached portions of the gelatin. Using dyes which were absorbed only by the gelatin, the negative that recorded the blue and green light was dyed red-orange. The result was a pair of positive dye images, the plates were then assembled emulsion to emulsion, producing a transparency that was capable of surprisingly good color rendition of skin tones in portraits. Capstaffs Kodachrome was made available in 1915. It was also adapted for use as a 35 mm motion picture film process, today, this first version of Kodachrome is nearly forgotten, completely overshadowed by the next Kodak product bearing the name Kodachrome
30.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
31.
Photography
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Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic sensor, this produces an electrical charge at each pixel. A negative image on film is used to photographically create a positive image on a paper base, known as a print. The word photography was created from the Greek roots φωτός, genitive of φῶς, light and γραφή representation by means of lines or drawing, several people may have coined the same new term from these roots independently. Johann von Maedler, a Berlin astronomer, is credited in a 1932 German history of photography as having used it in an article published on 25 February 1839 in the German newspaper Vossische Zeitung. Both of these claims are now widely reported but apparently neither has ever been confirmed as beyond reasonable doubt. Credit has traditionally given to Sir John Herschel both for coining the word and for introducing it to the public. Photography is the result of combining several technical discoveries, later Greek mathematicians Aristotle and Euclid also independently described a pinhole camera in the 5th and 4th centuries BCE. Daniele Barbaro described a diaphragm in 1566, wilhelm Homberg described how light darkened some chemicals in 1694. The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, the discovery of the camera obscura that provides an image of a scene dates back to ancient China. Leonardo da Vinci mentions natural camera obscura that are formed by dark caves on the edge of a sunlit valley, a hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the birth of photography was primarily concerned with inventing means to capture, renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means dark chamber in Latin and it is a box with a hole in it which allows light to go through and create an image onto the piece of paper. Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over, the first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a later attempt to make prints from it. Niépce was successful again in 1825, in 1826 or 1827, he made the View from the Window at Le Gras, the earliest surviving photograph from nature. Because Niépces camera photographs required a long exposure, he sought to greatly improve his bitumen process or replace it with one that was more practical. With an eye to eventual commercial exploitation, the partners opted for total secrecy, Daguerres efforts culminated in what would later be named the daguerreotype process
32.
35 mm equivalent focal length
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In photography, the 35 mm equivalent focal length is a measure that indicates the angle of view of a particular combination of a camera lens and film or sensor size. The term is useful because most photographers experienced with interchangeable lenses are most familiar with the 35 mm film format, on any 35 mm film camera, a 28 mm lens is a wide-angle lens, and a 200 mm lens is a long-focus lens. The 35 mm equivalent focal length of a particular combination is the focal length that one would need for a 35 mm film camera to obtain the same angle of view. Most commonly, the 35 mm equivalent focal length is based on equal diagonal angle of view and this definition also in the CIPA guideline DCG-001. Alternatively, it may sometimes be based on angle of view. 35 mm equivalent focal lengths are calculated by multiplying the focal length of the lens by the crop factor of the sensor. Quoted 35 mm equivalent focal lengths typically ignore depth of field, the perceived DOF of smaller sensors is deeper due to the shorter focal length lenses. Equivalent depth of field can be calculated the same way using the crop factor, a standard 35 mm film image is 36 mm wide by 24 mm tall, and the diagonal is 43.3 mm. This is because these sensor size specifications refer to the size of a camera tube, tubes are not used on digital cameras, but the same specifications are used. Apart from the width- and diagonal-based 35 mm equivalent focal length definitions, there is a definition, EFL =50 f /d mm. However. Focal Length Conversion for medium format and large format, at photo. net Focal Length at dpreview
33.
Angle of view
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In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the general term field of view. It is important to distinguish the angle of view from the angle of coverage, typically the image circle produced by a lens is large enough to cover the film or sensor completely, possibly including some vignetting toward the edge. A cameras angle of view not only on the lens. Digital sensors are usually smaller than 35mm film, and this causes the lens to have an angle of view than with 35mm film. In everyday digital cameras, the factor can range from around 1, to 1.6. For lenses projecting rectilinear images of distant objects, the focal length. Calculations for lenses producing non-rectilinear images are more complex and in the end not very useful in most practical applications. Angle of view may be measured horizontally, vertically, or diagonally, for example, for 35mm film which is 36 mm wide and 24mm high, d =36 mm would be used to obtain the horizontal angle of view and d =24 mm for the vertical angle. Because this is a function, the angle of view does not vary quite linearly with the reciprocal of the focal length. However, except for wide-angle lenses, it is reasonable to approximate α ≈ d f radians or 180 d π f degrees. The effective focal length is equal to the stated focal length of the lens. Angle of view can also be determined using FOV tables or paper or software lens calculators, consider a 35 mm camera with a lens having a focal length of F =50 mm. The dimensions of the 35 mm image format are 24 mm ×36 mm, here α is defined to be the angle-of-view, since it is the angle enclosing the largest object whose image can fit on the film. We want to find the relationship between, the angle α the opposite side of the triangle, d /2 the adjacent side, S2 Using basic trigonometry, we find. For macro photography, we neglect the difference between S2 and F. From the thin lens formula,1 F =1 S1 +1 S2, a second effect which comes into play in macro photography is lens asymmetry. The lens asymmetry causes an offset between the plane and pupil positions
34.
Aperture
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In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of a system determine the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of importance for the appearance at the image plane. If an aperture is narrow, then highly collimated rays are admitted, a wide aperture admits uncollimated rays, resulting in a sharp focus only for rays coming from a certain distance. This means that a wide aperture results in an image that is sharp for things at the correct distance, the aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane. In the human eye, the pupil is the aperture, an optical system typically has many openings or structures that limit the ray bundles. In general, these structures are called stops, and the stop is the stop that primarily determines the ray cone angle. In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the stop or the opening itself. For example, in a telescope, the stop is typically the edges of the objective lens or mirror. One then speaks of a telescope as having, for example, note that the aperture stop is not necessarily the smallest stop in the system. Magnification and demagnification by lenses and other elements can cause a large stop to be the aperture stop for the system. In astrophotography, the aperture may be given as a measure or as the dimensionless ratio between that measure and the focal length. In other photography, it is given as a ratio. Sometimes stops and diaphragms are called apertures, even when they are not the stop of the system. The word aperture is used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy, for example, a photometric aperture around a star usually corresponds to a window around the image of a star within which the light intensity is assumed. The aperture stop is an important element in most optical designs and its most obvious feature is that it limits the amount of light that can reach the image/film plane. This can be unavoidable, as in a telescope where one wants to collect as much light as possible, or deliberate
