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Hermann Wilhelm Vogel
Hermann Wilhelm Vogel (26 March 1834 – 17 December 1898) was a German photochemist and photographer who discovered dye sensitization, which is of great importance to photography. Academic career After finishing school in Frankfurt (Oder), he studied at the Royal Industrial Institute of Berlin, earning his Ph.D. with Karl Friedrich August Rammelsberg in 1863. Vogel's thesis, which was published in ''Poggendorffs Annalen'' , had the title: ''Über das Verhalten des Chlorsilbers, Bromsilbers und Iodsilbers im Licht und die Theorie der Photographie'' (Reactions of Silver Chloride, Silver Bromide and Silver Iodide with Light and the Theory of Photography). This marked the beginning of his research into the photographic process. From 1860 until 1865, he was an assistant in the mineralogical museum of the University of Berlin. From 1864 he was a professor at the Technische Hochschule in Charlottenburg (today Technische Universität Berlin), where he introduced photography as a f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kurrent
() is an old form of German-language handwriting based on late medieval cursive writing, also known as ("cursive script"), ("German script"), and ''German cursive''. Over the history of its use into the first part of the 20th century, many individual letters acquired variant forms. German writers used both cursive styles, and Latin cursive, in parallel: Location, contents, and context of the text determined which script style to use. is a modern script based on that is characterized by simplified letters and vertical strokes. It was developed in 1911 and taught in all German schools as the primary script from 1915 until the beginning of January 1941. Then it was replaced with ("normal German handwriting"), which is sometimes referred to as "Latin writing". Lettering examples File:Lessing Kleist-Brief.jpg, Letter from Lessing to Kleist, 14 March 1758 File:Schein und Sein.jpg, Manuscript by Wilhelm Busch (undated, late 19th century) File:Bielsko-Biała Teatr Polski ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver Iodide
Silver iodide is an inorganic compound with the formula Ag I. The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a grey colouration. The silver contamination arises because some samples of AgI can be highly photosensitive. This property is exploited in silver-based photography. Silver iodide is also used as an antiseptic and in cloud seeding. Structure The structure adopted by silver iodide is temperature dependent: * Below 420 K, the β phase of AgI, with the wurtzite structure, is most stable. This phase is encountered in nature as the mineral iodargyrite. * Above 420 K, the α phase becomes more stable. This motif is a body-centered cubic structure which has the silver centers distributed randomly between 6 octahedral, 12 tetrahedral and 24 trigonal sites. At this temperature, Ag+ ions can move rapidly through the solid, allowing fast ion conduction. The transition between the β and α forms repre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black-and-white
Black-and-white (B&W or B/W) images combine black and white to produce a range of achromatic brightnesses of grey. It is also known as greyscale in technical settings. Media The history of various visual media began with black and white, and as technology improved, altered to color. However, there are exceptions to this rule, including black-and-white fine art photography, as well as many film motion pictures and art film(s). Early photographs in the late 19th and early to mid 20th centuries were often developed in black and white, as an alternative to sepia due to limitations in film available at the time. Black and white was also prevalent in early television broadcasts, which were displayed by changing the intensity of monochrome phosphurs on the inside of the screen, before the introduction of colour from the 1950s onwards. Black and white continues to be used in certain sections of the modern arts field, either stylistically or to invoke the perception of a hist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Klaus Hentschel
Klaus Hentschel (born 4 April 1961) is a German physicist, historian of science and professor. He is the head of the University of Stuttgart's History of Science and Technology section of its History department. Life and work Born in Bad Nauheim, Hentschel from 1979 to 1985 studied physics, philosophy, science, history and musicology at the University of Hamburg. He completed his studies in philosophy in 1985 with the master's examination, and a study in physics in 1987. After some studies in the United States, among others in Boston on a DAAD, he in 1989 received his PhD at the University of Hamburg. His thesis was entitled "Interpretationen und Fehlinterpretationen der speziellen und der allgemeinen Relativitätstheorie durch Zeitgenossen Albert Einsteins" (Interpretations and misinterpretations of the special and general relativity theory by Albert Einstein's contemporaries). After graduation Hentschel participated in a research project by the Deutsche Forschungsgemeinschaf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fraunhofer Lines
The Fraunhofer lines are a set of spectral absorption lines. They are dark absorption lines, seen in the optical spectrum of the Sun, and are formed when atoms in the solar atmosphere absorb light being emitted by the solar photosphere. The lines are named after German physicist Joseph von Fraunhofer, who observed them in 1814. Discovery In 1802, English chemist William Hyde WollastonMelvyn C. UsselmanWilliam Hyde WollastonEncyclopædia Britannica, retrieved 31 March 2013 was the first person to note the appearance of a number of dark features in the solar spectrum. In 1814, Joseph von Fraunhofer independently rediscovered the lines and began to systematically study and measure their wavelengths. He mapped over 570 lines, designating the most prominent with the letters A through K and weaker lines with other letters. Modern observations of sunlight can detect many thousands of lines. About 45 years later, Gustav Kirchhoff and Robert Bunsen noticed that several Fraunhofer li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visible Spectrum
The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic spectrum as well, known collectively as ''optical radiation''. A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400–790 Terahertz (unit), terahertz. These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aniline
Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starting material for fine chemical synthesis. Its main use is in the manufacture of precursors to polyurethane, dyes, and other industrial chemicals. Like most volatile amines, it has the odor of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. It is toxic to humans. Relative to benzene, aniline is "electron-rich". It thus participates more rapidly in electrophilic aromatic substitution reactions. Likewise, it is also prone to oxidation: while freshly purified aniline is an almost colorless oil, exposure to air results in gradual darkening to yellow or red, due to the formation of strongly colored, oxidized impurities. Ani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anti-halation Backing
An anti-halation backing is a layer found in many photographic films—and almost all film intended for motion picture cameras—usually a coating on the back of the film base, though it is sometimes incorporated between the light-sensitive photographic emulsion, emulsion and the base. Its purpose is to absorb light that passes through the emulsion, thus preventing any light from being reflected back through the emulsion from the rear surface of the base, or from anything behind the film, such as the pressure plate of the camera. This prevents a halo (optical phenomenon), halo-like effect (halation) from forming around bright points or edges in the image. Still cameras, which handle less film and thus contend with less wear, typically hold their film in the gate with components painted or treated to be black, so reflections are less of an issue and few still films made use of anti-halation backings. The notable exception was Kodak's Kodachrome, which incorporated such a backing t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dry Plate
The gelatin silver print is the most commonly used chemical process in black-and-white photography, and is the fundamental chemical process for modern analog color photography. As such, films and printing papers available for analog photography rarely rely on any other chemical process to record an image. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. The "dry plate" gelatin process was an improvement on the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating. History Gelatine was used to copy the images of Daguerreotypes by 1845 and Alphonse Louis Poitevin wrote about positive proofs of negatives on dry gelatine plates in 1850. In the 1860s, the dr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver Bromide
Silver bromide (AgBr), a soft, pale-yellow, water-insoluble salt well known (along with other silver halides) for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgBr is widely used in photographic films and is believed by some to have been used for faking the Shroud of Turin. The salt can be found naturally as the mineral bromargyrite (bromyrite). Preparation Although the compound can be found in mineral form, AgBr is typically prepared by the reaction of silver nitrate with an alkali bromide, typically potassium bromide: :AgNO3(aq) + KBr(aq) → AgBr(s)+ KNO3(aq) Although less convenient, the salt can also be prepared directly from its elements. Modern preparation of a simple, light-sensitive surface involves forming an emulsion of silver halide crystals in a gelatine, which is then coated onto a film or other support. The crystals are formed by precipitation in a controlled environment to prod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collodion
Collodion is a flammable, syrupy solution of nitrocellulose in Diethyl ether, ether and Alcohol (chemistry), alcohol. There are two basic types: flexible and non-flexible. The flexible type is often used as a surgical dressing or to hold dressings in place. When painted on the skin, collodion dries to form a flexible nitrocellulose film. While it is initially colorless, it discolors over time. Non-flexible collodion is often used in theatrical make-up. Collodion was also the basis of most Collodion process, wet-plate photography until it was superseded by modern gelatin emulsions. History In 1846, Louis-Nicolas Ménard and Florès Domonte discovered that cellulose nitrate could be dissolved in diethyl ether, ether. They devised a mixture of ether as the solvent and ethanol as a diluent that rendered cellulose nitrate into a clear gelatinous liquid. Collodion was first used medically as a dressing in 1847 by the Boston physician John Parker Maynard. The solution was dubbed "collodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visible Spectrum
The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic spectrum as well, known collectively as ''optical radiation''. A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400–790 Terahertz (unit), terahertz. These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
