A silver halide is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, chlorine and fluorine may each combine with silver to produce silver bromide, silver chloride, silver iodide, three forms of silver fluoride, respectively; as a group, they are referred to as the silver halides, are given the pseudo-chemical notation AgX. Although most silver halides involve silver atoms with oxidation states of +1, silver halides in which the silver atoms have oxidation states of +2 are known, of which silver fluoride is the only known stable one. Silver halides are light-sensitive chemicals, are used in photographic film and paper. Silver halides are used in photographic film and photographic paper, including graphic art film and paper, where silver halide crystals in gelatin are coated on to a film base, glass or paper substrate; the gelatin is a vital part of the emulsion as the protective colloid of appropriate physical and chemical properties.
Gelatin may contain trace elements which increase the light sensitivity of the emulsion, although modern practice uses gelatin without such components. When absorbed by an AgX crystal, photons cause electrons to be promoted to a conduction band which can be attracted by a sensitivity speck, a shallow electron trap, which may be a crystalline defect or a cluster of silver sulfide, other trace elements, or combination thereof, combined with an interstitial silver ion to form silver metal speck; when a silver halide crystal is exposed to light, a sensitivity speck on the surface of the crystal is turned into a small speck of metallic silver. If the speck of silver contains four or more atoms, it is rendered developable - meaning that it can undergo development which turns the entire crystal into metallic silver. 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 and tonal qualities desired in the product.
Silver iodide is always combined with silver bromide or silver chloride, except in the case of some historical processes such as the collodion wet plate and daguerreotype, in which the iodide is sometimes used alone. 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; the three main silver halide compounds have distinctive colours that can be used to 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 increase or decrease the solubility of AgX. Examples of compounds that increase the solubility include: cyanide, thiosulfate, amines, sulfite, crown ether. Examples of compounds that reduces the solubility include many organic thiols and nitrogen compounds that do not possess solubilizing group other than mercapto group or the nitrogen site, such as mercaptooxazoles, mercaptotetrazoles 1-phenyl-5-mercaptotetrazole, benzimidazoles 2-mercaptobenzimidazole and these compounds further substituted by hydrophobic groups.
Compounds such as thiocyanate and thiosulfate enhance solubility when they are present in a sufficiently large quantity, due to formation of soluble complex ions, but they significantly depress solubility when present in a small quantity, due to formation of sparingly soluble complex ions. 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
In photography, a negative is an image on a strip or sheet of transparent plastic film, in which the lightest areas of the photographed subject appear darkest and the darkest areas appear lightest. This reversed order occurs because the light-sensitive chemicals a camera film must use to capture an image enough for ordinary picture-taking are darkened, rather than bleached, by exposure to light and subsequent photographic processing. In the case of color negatives, the colors are reversed into their respective complementary colors. Typical color negatives have an overall dull orange tint due to an automatic color-masking feature that results in improved color reproduction. Negatives are used to make positive prints on photographic paper by projecting the negative onto the paper with a photographic enlarger or making a contact print; the paper is darkened in proportion to its exposure to light, so a second reversal results which restores light and dark to their normal order. Negatives were once made on a thin sheet of glass rather than a plastic film, some of the earliest negatives were made on paper.
It is incorrect to call an image a negative because it is on a transparent material. Transparent prints can be made by printing a negative onto special positive film, as is done to make traditional motion picture film prints for use in theaters; some films used in cameras are designed to be developed by reversal processing, which produces the final positive, instead of a negative, on the original film. Positives on film or glass are known as transparencies or diapositives, if mounted in small frames designed for use in a slide projector or magnifying viewer they are called slides. A positive image is a normal image. A negative image is a total inversion, in which light areas appear vice versa. A negative color image is additionally color-reversed, with red areas appearing cyan, greens appearing magenta, blues appearing yellow, vice versa. Film negatives have less contrast, but a wider dynamic range, than the final printed positive images; the contrast increases when they are printed onto photographic paper.
When negative film images are brought into the digital realm, their contrast may be adjusted at the time of scanning or, more during subsequent post-processing. Film for cameras that use the 35 mm still format is sold as a long strip of emulsion-coated and perforated plastic spooled in a light-tight cassette. Before each exposure, a mechanism inside the camera is used to pull an unexposed area of the strip out of the cassette and into position behind the camera lens; when all exposures have been made the strip is rewound into the cassette. After the film is chemically developed, the strip shows a series of small negative images, it is then cut into sections for easier handling. Medium format cameras use 120 film, which yields a strip of negatives 60 mm wide, large format cameras capture each image on a single sheet of film which may be as large as 20 x 25 cm or larger; each of these photographed images may be referred to as a negative and an entire strip or set of images may be collectively referred to as "the negatives".
They are the master images, from which all positive prints will derive, so they are handled and stored with special care. Many photographic processes create negative images: the chemicals involved react when exposed to light, so that during development they produce deposits of microscopic dark silver particles or colored dyes in proportion to the amount of exposure. However, when a negative image is created from a negative image a positive image results; this makes most chemical-based photography a two-step process, which uses negative film and ordinary processing. Special films and development processes have been devised so that positive images can be created directly on the film. Despite the market's evolution away from film, there is still a desire and market for products which allow fine art photographers to produce negatives from digital images for their use in alternative processes such as cyanotypes, gum bichromate, platinum prints, many others; the 1980s TV show Tales from the Darkside opening sequence famously shows various images of a countryside, covered bridge, farm buildings, birch trees that flip over to another image of the countryside fading into a negative image.
The title appears and a door in the image opens to reveal the episode. Scanning film negatives at the Wayback Machine
The Hudson River is a 315-mile river that flows from north to south through eastern New York in the United States. The river originates in the Adirondack Mountains of Upstate New York, flows southward through the Hudson Valley to the Upper New York Bay between New York City and Jersey City, it drains into the Atlantic Ocean at New York Harbor. The river serves as a political boundary between the states of New Jersey and New York at its southern end. Further north, it marks local boundaries between several New York counties; the lower half of the river is a tidal estuary, deeper than the body of water into which it flows, occupying the Hudson Fjord, an inlet which formed during the most recent period of North American glaciation, estimated at 26,000 to 13,300 years ago. Tidal waters influence the Hudson's flow from as far north as the city of Troy; the river is named after Henry Hudson, an Englishman sailing for the Dutch East India Company, who explored it in 1609, after whom Hudson Bay in Canada is named.
It had been observed by Italian explorer Giovanni da Verrazzano sailing for King Francis I of France in 1524, as he became the first European known to have entered the Upper New York Bay, but he considered the river to be an estuary. The Dutch called the river the North River – with the Delaware River called the South River – and it formed the spine of the Dutch colony of New Netherland. Settlements of the colony clustered around the Hudson, its strategic importance as the gateway to the American interior led to years of competition between the English and the Dutch over control of the river and colony. During the eighteenth century, the river valley and its inhabitants were the subject and inspiration of Washington Irving, the first internationally acclaimed American author. In the nineteenth century, the area inspired the Hudson River School of landscape painting, an American pastoral style, as well as the concepts of environmentalism and wilderness; the Hudson was the eastern outlet for the Erie Canal, when completed in 1825, became an important transportation artery for the early-19th-century United States.
The source of the Hudson River is Lake Tear of the Clouds in the Adirondack Park at an altitude of 4,322 feet. However, the river is not cartographically called the Hudson River until miles downstream; the river is named Feldspar Brook until its confluence with Calamity Brook, is named Calamity Brook until the river reaches Indian Pass Brook, flowing south from the outlet of Henderson Lake. From that point on, the stream is cartographically known as the Hudson River; the U. S. Geological Survey uses this cartographical definition; the longest source of the Hudson River as shown on the most detailed USGS maps is the "Opalescent River" on the west slopes of Little Marcy Mountain, originating two miles north of Lake Tear of the Clouds, several miles, past the Flowed Lands, to the Hudson River. And a mile longer than "Feldspar Brook", which flows out of that lake in the Adirondack Mountains. Popular culture and convention, more cite the photogenic Lake Tear of the Clouds as the source. Using river names as seen on maps, Indian Pass Brook flows into Henderson Lake, the outlet from Henderson Lake flows east and meets the southwest flowing Calamity Brook.
The confluence of the two rivers is. South of the outlet of Sanford Lake, the Opalescent River flows into the Hudson; the Hudson flows south, taking in Beaver Brook and the outlet of Lake Harris. After its confluence with the Indian River, the Hudson forms the boundary between Essex and Hamilton counties. In the hamlet of North River, the Hudson flows in Warren County and takes in the Schroon River. Further south, the river forms the boundary between Saratoga Counties; the river takes in the Sacandaga River from the Great Sacandaga Lake. Shortly thereafter, the river leaves the Adirondack Park, flows under Interstate 87, through Glens Falls, just south of Lake George although receiving no streamflow from the lake, it next goes through Hudson Falls. At this point the river forms the boundary between Saratoga Counties. Here the river has an elevation of 200 feet. Just south in Fort Edward, the river reaches its confluence with the Champlain Canal, which provided boat traffic between New York City and Montreal and the rest of Eastern Canada via the Hudson, Lake Champlain and the Saint Lawrence Seaway.
Further south the Hudson takes in water from the Batten Kill River and Fish Creek near Schuylerville. The river forms the boundary between Saratoga and Rensselaer counties; the river enters the heart of the Capital District. It takes in water from the Hoosic River. Shortly thereafter the river has its confluence with the Mohawk River, the largest tributary of the Hudson River, in Waterford; the river reaches the Federal Dam in Troy, marking an impoundment of the river. At an elevation of 2 feet, the bottom of the dam marks the beginning of the tidal influence in the Hudson as well as the beginning of the lower Hudson River. South of the Federal Dam, the Hudson River begins to widen considerably; the river enters the Hudson Valley, flowing along the west bank of Albany and the east bank of Rensselaer. Interstate 90 crosses the Hudson into Albany at this point in the river; the Hudson leaves the Capital District, forming the boundary between Greene and Columbia Counties. It meets its confluence with Schodack Creek, widening at this point.
After flowing by Hudson, the river forms the boundary between Ulster and Columbia Counties and Ulster and Dutchess Counties, passing Germantown and Kingston. The Delaware and Hudson Canal meets the river at t
XP is a chromogenic black-and-white film from Ilford Photo. It was launched to great acclaim at photokina in September 1980, went on sale in January, 1981, it has since progressed with XP2 Super being the latest. The main competitor of Ilford XP2 Super was Kodak BW400CN, discontinued in 2014; as of 2018, Ilford XP2 Super and Fuji Neopan 400CN are the only black & white films on the market that can be developed using the C-41 process. As a chromogenic film, XP2 can scan well because it avoids the limitations of Digital ICE, plus it has a similar exposure latitude to color negative film, so it can be exposed with an exposure index from ISO 50/18° to 800/30° on a single roll and be developed in traditional C-41 processing. In 2013, Ilford introduced a version of their black-and-white single-use camera which includes 27 exposures of XP2 Super film. Ilford XP2 Super How To Shoot Ilford XP2 Super
Photographic paper is a paper coated with a light-sensitive chemical formula, used for making photographic prints. When photographic paper is exposed to light, it captures a latent image, developed to form a visible image; the light-sensitive layer of the paper is called the emulsion. The most common chemistry was based on silver salts but other alternatives have been used; the print image is traditionally produced by interposing a photographic negative between the light source and the paper, either by direct contact with a large negative or by projecting the shadow of the negative onto the paper. The initial light exposure is controlled to produce a gray scale image on the paper with appropriate contrast and gradation. Photographic paper may be exposed to light using digital printers such as the LightJet, with a camera, by scanning a modulated light source over the paper, or by placing objects upon it. Despite the introduction of digital photography, photographic papers are still sold commercially.
Photographic papers are manufactured in paper weights and surface finishes. A range of emulsions are available that differ in their light sensitivity, colour response and the warmth of the final image. Color papers are available for making colour images; the effect of light in darkening a prepared paper was discovered by Thomas Wedgwood in 1802. Photographic papers have been used since the beginning of all negative–positive photographic processes as developed and popularized by William Fox Talbot. After the early days of photography, papers have been manufactured on a large scale with improved consistency and greater light sensitivity. Photographic papers fall into one of three sub-categories: Papers used for negative-positive processes; this includes all chromogenic colour papers. Papers used for positive-positive processes. Papers used for positive-positive film-to-paper processes where a positive image is enlarged and copied onto a photographic paper, for example the Ilfochrome process. All photographic papers consist of a light-sensitive emulsion, consisting of silver halide salts suspended in a colloidal material - gelatin- coated onto a paper, resin coated paper or polyester support.
In black-and-white papers, the emulsion is sensitised to blue and green light, but is insensitive to wavelengths longer than 600 nm in order to facilitate handling under red or orange safelighting. In Chromogenic colour papers, the emulsion layers are sensitive to red and blue light producing cyan and yellow dye during processing. Modern black-and-white papers are coated on a small range of bases. In the past, linen has been used as a base material. Fiber-based photographic papers consist of a paper base coated with baryta. Tints are sometimes added to the baryta to add subtle colour to the final print. Most fiber-based papers include a clear hardened gelatin layer above the emulsion which protects it from physical damage during processing; this is called a supercoating. Papers without a supercoating are suitable for use with the bromoil process. Fiber-based papers are chosen as a medium for high-quality prints for exhibition and archiving purposes; these papers require careful processing and handling when wet.
However, they are easier to hand-colour and retouch than resin-coated equivalents. The paper base of resin-coated papers is sealed by two polyethylene layers, making it impenetrable to liquids. Since no chemicals or water are absorbed into the paper base, the time needed for processing and drying durations are reduced in comparison to fiber-based papers. Resin paper prints dried within twenty to thirty minutes. Resin-coated papers have improved dimensional stability, do not curl upon drying; the term baryta derives from the name of barite. However, the substance used to coat photographic papers is not pure barium sulfate, but a mixture of barium and strontium sulfates; the ratio of strontium to barium differs among commercial photographic papers, so chemical analysis can be used to identify the maker of the paper used to make a print and sometimes when the paper was made. The baryta layer has two functions 1) to brighten the image and 2) to prevent chemicals adsorbed on the fibers from infiltrating the gelatin layer.
The brightening occurs because barium sulfate is in the form of a fine precipitate that scatters light back through the silver image layer. In the early days of photography, before baryta layers were used, impurities from the paper fibers could diffuse into the silver layer and cause an uneven loss of sensitivity or mottle the silver image. All colour photographic materials available today are coated on either RC paper or on solid polyester; the photographic emulsion used for colour photographic materials consists of three colour emulsion layers along with other supporting layers. The colour layers are sensitised to their corresponding colours. Although it is believe
Black and white
Black-and-white images combine black and white in a continuous spectrum, producing a range of shades of gray. The history of various visual media has begun with black and white, as technology improved, altered to color. However, there are exceptions to this rule, including black-and-white fine art photography and in motion pictures, many art films. Most early forms of motion pictures or film were white; some color film processes, including hand coloring were experimented with, in limited use, from the earliest days of motion pictures. The switch from most films being in black-and-white to most being in color was gradual, taking place from the 1930s to the 1960s; when most film studios had the capability to make color films, the technology's popularity was limited, as using the Technicolor process was expensive and cumbersome. For many years, it was not possible for films in color to render realistic hues, thus its use was restricted to historical films and cartoons until the 1950s, while many directors preferred to use black-and-white stock.
For the years 1940–1966, a separate Academy Award for Best Art Direction was given for black-and-white movies along with one for color. The earliest television broadcasts were transmitted in black-and-white, received and displayed by black-and-white only television sets. Scottish inventor John Logie Baird demonstrated the world's first color television transmission on July 3, 1928 using a mechanical process; some color broadcasts in the U. S. began in the 1950s, with color becoming common in western industrialized nations during the late 1960s. In the United States, the Federal Communications Commission settled on a color NTSC standard in 1953, the NBC network began broadcasting a limited color television schedule in January 1954. Color television became more widespread in the U. S. between 1963 and 1967, when major networks like CBS and ABC joined NBC in broadcasting full color schedules. Some TV stations in the US were still broadcasting in B&W until the late 80s to early 90s, depending on network.
Canada began airing color television in 1966 while the United Kingdom began to use an different color system from July 1967 known as PAL. The Republic of Ireland followed in 1970. Australia experimented with color television in 1967 but continued to broadcast in black-and-white until 1975, New Zealand experimented with color broadcasting in 1973 but didn't convert until 1975. In China, black-and-white television sets were the norm until as late as the 1990s, color TVs not outselling them until about 1989. In 1969, Japanese electronics manufacturers standardized the first format for industrial/non-broadcast videotape recorders called EIAJ-1, which offered only black-and-white video recording and playback. While used professionally now, many consumer camcorders have the ability to record in black-and-white. Throughout the 19th century, most photography was monochrome photography: images were either black-and-white or shades of sepia. Personal and commercial photographs might be hand tinted. Colour photography was rare and expensive and again containing inaccurate hues.
Color photography became more common from the mid-20th century. However, black-and-white photography has continued to be a popular medium for art photography, as shown in the picture by the well-known photographer Ansel Adams; this can take the form of black-and-white film or digital conversion to grayscale, with optional digital image editing manipulation to enhance the results. For amateur use certain companies such as Kodak manufactured black-and-white disposable cameras until 2009. Certain films are produced today which give black-and-white images using the ubiquitous C41 color process. Printing is an ancient art, color printing has been possible in some ways from the time colored inks were produced. In the modern era, for financial and other practical reasons, black-and-white printing has been common through the 20th century. However, with the technology of the 21st century, home color printers, which can produce color photographs, are common and inexpensive, a technology unimaginable in the mid-20th century.
Most American newspapers were black-and-white until the early 1980s. Some claim. In the UK, color was only introduced from the mid-1980s. Today, many newspapers restrict color photographs to the front and other prominent pages since mass-producing photographs in black-and-white is less expensive than color. Daily comic strips in newspapers were traditionally black-and-white with color reserved for Sunday strips.:Color printing is more expensive. Sometimes color is reserved for the cover. Magazines such as Jet magazine were either all or black-and-white until the end of the 2000s when it became all-color. Manga are published in black-and-white although now it is part of its image. Many school yearbooks are still or in black-and-white; the Wizard of Oz is in color when Dorothy is in Oz, but in black-and-white when she is in Kansas, although the latter scenes were in sepia when the film was released. The British film A Matter of Life and Death depicts the other world in black-and-white, earthly events in color.
Wim Wenders's film Wings of Desire uses sepia-tone black-and-white f
CMYK color model
The CMYK color model is a subtractive color model, used in color printing, is used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta and key; the CMYK model works by or masking colors on a lighter white, background. The ink reduces the light; such a model is called subtractive because inks "subtract" the colors red and blue from white light. White light minus red leaves cyan, white light minus green leaves magenta, white light minus blue leaves yellow. In additive color models, such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, to produce deeper black tones and dark colors are produced by using black ink instead of the combination of cyan and yellow. With CMYK printing, halftoning allows for less than full saturation of the primary colors.
Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter and less saturated than the color of pure magenta ink. Without halftoning, the three primary process colors could be printed only as solid blocks of color, therefore could produce only seven colors: the three primaries themselves, plus three secondary colors produced by layering two of the primaries: cyan and yellow produce green and magenta produce blue and magenta produce red, plus layering all three of them resulting in black. With halftoning, a full continuous range of colors can be produced. To improve print quality and reduce moiré patterns, the screen for each color is set at a different angle. While the angles depend on how many colors are used and the preference of the press operator, typical CMYK process printing uses any of the following screen angles: The "black" generated by mixing commercially practical cyan and yellow inks is unsatisfactory, so four-color printing uses black ink in addition to the subtractive primaries.
Common reasons for using black ink include: In traditional preparation of color separations, a red keyline on the black line art marked the outline of solid or tint color areas. In some cases a black keyline was used when it served as both a color indicator and an outline to be printed in black; because the black plate contained the keyline, the K in CMYK represents the keyline or black plate sometimes called the key plate. Text is printed in black and includes fine detail, so to reproduce text or other finely detailed outlines, without slight blurring, using three inks would require impractically accurate registration. A combination of 100% cyan and yellow inks soaks the paper with ink, making it slower to dry, causing bleeding, or weakening the paper so much that it tears. Although a combination of 100% cyan and yellow inks should, in theory absorb the entire visible spectrum of light and produce a perfect black, practical inks fall short of their ideal characteristics and the result is a dark muddy color that does not quite appear black.
Adding black ink absorbs more light and yields much better blacks. Using black ink is less expensive than using the corresponding amounts of colored inks; when a dark area is desirable, a colored or gray CMY "bedding" is applied first a full black layer is applied on top, making a rich, deep black. A black made with just CMY inks is sometimes called a composite black; the amount of black to use to replace amounts of the other ink is variable, the choice depends on the technology and ink in use. Processes called under color removal, under color addition, gray component replacement are used to decide on the final mix. CMYK or process color printing is contrasted with spot color printing, in which specific colored inks are used to generate the colors appearing on paper; some printing presses are capable of printing with both four-color process inks and additional spot color inks at the same time. High-quality printed materials, such as marketing brochures and books include photographs requiring process-color printing, other graphic effects requiring spot colors, finishes such as varnish, which enhances the glossy appearance of the printed piece.
CMYK are the process printers which have a small color gamut. Processes such as Pantone's proprietary six-color Hexachrome expand the gamut. Light, saturated colors cannot be created with CMYK, light colors in general may make visible the halftone pattern. Using a CcMmYK process, with the addition of light cyan and magenta inks to CMYK, can solve these problems, such a process is used by many inkjet printers, including desktop models. Comparisons between RGB displays and CMYK prints can be difficult, since the color reproduction technologies and properties are different. A computer monitor mixes shades of red and blue light to create color pictures. A CMYK printer instead uses light-absorbing cyan and yellow inks, whose colors are mixed using dithering, halftoning, or some other optical technique. Similar to monitors, the inks used in printing produ