1.
View from the Window at Le Gras
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View from the Window at Le Gras is a heliographic image and the oldest surviving camera photograph. It was created by Nicéphore Niépce in 1826 or 1827 at Saint-Loup-de-Varennes, France, Niépce captured the scene with a camera obscura focused onto a 16.2 cm ×20.2 cm pewter plate thinly coated with Bitumen of Judea, a naturally occurring asphalt. The bitumen hardened in the brightly lit areas, but in the dimly lit areas it remained soluble and could be washed away with a mixture of oil of lavender, a very long exposure in the camera was required. Sunlight strikes the buildings on opposite sides, suggesting an exposure that lasted eight hours. A researcher who studied Niépces notes and recreated his processes found that the exposure must have continued for several days, in late 1827, Niépce visited England. He showed this and several specimens of his work to botanical illustrator Francis Bauer. View from the Window at Le Gras was the example of a camera photograph. Bauer encouraged him to present his heliography process to the Royal Society, before returning to France, Niépce gave his paper and the specimens to Bauer. Niépce died suddenly in 1833, due to a stroke, on March 9,1839, the specimens were finally exhibited at the Royal Society. After Bauers death in 1840 they passed through several hands and were exhibited as historical curiosities. View from the Window at Le Gras was last seen in 1905, historian Helmut Gernsheim tracked down the photograph in 1952 and brought it to prominence, reinforcing the claim that Niépce is the inventor of photography. Gernsheim heavily retouched one of the prints to clean it up and make the scene more comprehensible. During the 1950s and early 1960s, Gernsheim lent the photograph to several exhibitions in continental Europe, in 1963, Harry Ransom purchased most of Gernsheims photography collection for the University of Texas at Austin. The Niépce heliograph was not included in the sale, but shortly afterward Gernsheim donated it, although it has rarely traveled since then, in 2012–13 it visited Mannheim, Germany, as part of an exhibition entitled The Birth of Photography—Highlights of the Helmut Gernsheim Collection. It is normally on display in the lobby of the Harry Ransom Humanities Research Center in Austin. They confirmed that the image consists of bitumen and that the plate is pewter. The Institute also designed and built the elaborate display case system that now houses the artifact in a continuously monitored, stabilized, in 2007, scientists from the Louvre Museum published an analysis of the photograph using ion beam analysis, with data taken on their 2 MV electrostatic accelerator. This showed the details of the process that was corroding the image
2.
Camera obscura
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The surroundings of the projected image have to be relatively dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms. The term camera obscura also refers to constructions or devices that use of the principle within a box. Camerae obscurae with a lens in the opening have been used since the second half of the 16th century, before the term camera obscura was first used in 1604, many other expressions were used including cubiculum obscurum, cubiculum tenebricosum, conclave obscurum and locus obscurus. Rays of light travel in straight lines and change when they are reflected and partly absorbed by an object, retaining information about the color, lit objects reflect rays of light in all directions. The human eye itself works much like a camera obscura with an opening, a biconvex lens, a camera obscura device consists of a box, tent or room with a small hole in one side. Light from a scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted and reversed. The image can be projected onto paper, and can then be traced to produce an accurate representation. In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, many camerae obscurae use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus. As the pinhole is made smaller, the image gets sharper, with too small a pinhole, however, the sharpness worsens, due to diffraction. Using mirrors, as in an 18th-century overhead version, it is possible to project a right-side-up image, another more portable type is a box with an angled mirror projecting onto tracing paper placed on the glass top, the image being upright as viewed from the back. There are theories that occurrences of camera obscura effects inspired paleolithic cave paintings and it is also suggested that camera obscura projections could have played a role in Neolithic structures. Perforated gnomons projecting an image of the sun were described in the Chinese Zhoubi Suanjing writings. The location of the circle can be measured to tell the time of day. In Arab and European cultures its invention was later attributed to Egyptian astronomer. Some ancient sightings of gods and spirits, especially in worship, are thought to possibly have been conjured up by means of camera obscura projections. In these writings it is explained how the image in a collecting-point or treasure house is inverted by an intersecting point that collected the light. Light coming from the foot of a person would partly be hidden below. Rays from the head would partly be hidden above and partly form the part of the image
3.
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
4.
Lavender oil
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Lavender oil is an essential oil obtained by distillation from the flower spikes of certain species of lavender. Like all essential oils, it is not a compound, it is a complex mixture of naturally occurring phytochemicals, including linalool. Kashmir Lavender oil is famous for being produced from lavender at the foothills of the Himalayas, as of 2011, the biggest lavender oil producer in the world is Bulgaria. Lavender oil has long used in the production of perfume. Oil of spike lavender was used as a solvent in oil painting, Lavender oil appears to be an endocrine disruptor, exhibiting anti-androgenic activity in vitro. The exact composition of lavender essential oil varies from species to species, of these linalool and linalyl acetate dominate, with moderate levels of lavandulyl acetate, terpinen-4-ol and lavandulol. 1, 8-cineole and camphor are also present in low to moderate qualities, in all lavender oil typically contains many more than 100 compounds, although a great many of these are present at very low concentrations. The composition of lavender essential oil as obtained by chromatography, Lavender Essential oil
5.
Geography
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Geography is a field of science devoted to the study of the lands, the features, the inhabitants, and the phenomena of Earth. The first person to use the word γεωγραφία was Eratosthenes, Geography is an all-encompassing discipline that seeks an understanding of the Earth and its human and natural complexities—not merely where objects are, but how they have changed and come to be. It is often defined in terms of the two branches of geography and physical geography. Geography has been called the world discipline and the bridge between the human and the physical sciences, Geography is a systematic study of the Earth and its features. Traditionally, geography has been associated with cartography and place names, although many geographers are trained in toponymy and cartology, this is not their main preoccupation. Geographers study the space and the temporal database distribution of phenomena, processes, because space and place affect a variety of topics, such as economics, health, climate, plants and animals, geography is highly interdisciplinary. The interdisciplinary nature of the approach depends on an attentiveness to the relationship between physical and human phenomena and its spatial patterns. Names of places. are not geography. know by heart a whole gazetteer full of them would not, in itself and this is a description of the world—that is Geography. In a word Geography is a Science—a thing not of mere names but of argument and reason, of cause, just as all phenomena exist in time and thus have a history, they also exist in space and have a geography. Geography as a discipline can be split broadly into two main fields, human geography and physical geography. The former largely focuses on the environment and how humans create, view, manage. The latter examines the environment, and how organisms, climate, soil, water. The difference between these led to a third field, environmental geography, which combines physical and human geography. Physical geography focuses on geography as an Earth science and it aims to understand the physical problems and the issues of lithosphere, hydrosphere, atmosphere, pedosphere, and global flora and fauna patterns. Physical geography can be divided into broad categories, including, Human geography is a branch of geography that focuses on the study of patterns. It encompasses the human, political, cultural, social, and it requires an understanding of the traditional aspects of physical and human geography, as well as the ways that human societies conceptualize the environment. Integrated geography has emerged as a bridge between the human and the geography, as a result of the increasing specialisation of the two sub-fields. Examples of areas of research in the environmental geography include, emergency management, environmental management, sustainability, geomatics is concerned with the application of computers to the traditional spatial techniques used in cartography and topography
6.
Heliograph
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A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter, the heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. Its main uses were military, survey and forest protection work, heliographs were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975. Most heliographs were variants of the British Army Mance Mark V version and it used a mirror with a small unsilvered spot in the centre. The sender aligned the heliograph to the target by looking at the target in the mirror. Keeping his head still, he adjusted the aiming rod so its cross wires bisected the target. This indicated that the sunbeam was pointing at the target, the flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. If the sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. If the sun was behind the sender, the rod was replaced by a second mirror, to capture the sunlight from the main mirror. The U. S. Signal Corps heliograph mirror did not tilt and this type produced flashes by a shutter mounted on a second tripod. The heliograph had some great advantages, however, anyone in the beam with the correct knowledge could intercept signals without being detected. In the Boer War, where both sides used heliographs, tubes were used to decrease the dispersion of the beam.5 degrees to 15 degrees. The distance that signals could be seen depended on the clarity of the sky. A clear line of sight was required, and since the Earths surface is curved, under ordinary conditions, a flash could be seen 30 miles with the naked eye, and much farther with a telescope. The maximum range was considered to be 10 miles for each inch of mirror diameter, mirrors ranged from 1.5 inches to 12 inches or more. The record distance was established by a detachment of U. S, the German professor Carl Friedrich Gauss of the University of Göttingen developed and used a predecessor of the heliograph in 1821. His device directed a beam of sunlight to a distant station to be used as a marker for geodetic survey work. Similarly, the story that a shield was used as a heliograph at the Battle of Marathon is a modern myth, what Herodotus did write was that someone was accused of having arranged to hold up a shield as a signal
7.
Heliotrope (instrument)
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The heliotrope is an instrument that uses a mirror to reflect sunlight over great distances to mark the positions of participants in a land survey. The heliotrope was invented in 1821 by the German mathematician Carl Friedrich Gauss, the word heliotrope is taken from the Greek, helios, meaning sun, and tropos, meaning turn. It is a name for an instrument which can be used to turn incoming sunlight. Heliotropes were used in surveys from Gausss survey in Germany in 1821 through the late 1980s, the Indian specification for heliotropes was updated in 1981, and the American military specification for heliotropes was retired on 8 December 1995. Heliotropes were often used as targets at ranges of over 100 miles. In California, in 1878, a heliotrope on Mount Saint Helena was surveyed by B. A. Colonna of the USCGS from Mount Shasta, a distance of 192 miles. The heliotrope was limited to use on days and was further limited to mornings. The inventor of the heliograph, a similar instrument specialized for signaling, was inspired by observing the use of heliotropes in the survey of India, transits of Venus Page with photographs of three heliotropes from 1873. Improvised Heliotrope this 1969 article also provides the US Army part number for a heliotrope, Heliotrope Heliotrope photo, description of a 192-mile record
8.
French (language)
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French is a Romance language of the Indo-European family. It descended from the Vulgar Latin of the Roman Empire, as did all Romance languages, French has evolved from Gallo-Romance, the spoken Latin in Gaul, and more specifically in Northern Gaul. Its closest relatives are the other langues doïl—languages historically spoken in northern France and in southern Belgium, French was also influenced by native Celtic languages of Northern Roman Gaul like Gallia Belgica and by the Frankish language of the post-Roman Frankish invaders. Today, owing to Frances past overseas expansion, there are numerous French-based creole languages, a French-speaking person or nation may be referred to as Francophone in both English and French. French is a language in 29 countries, most of which are members of la francophonie. As of 2015, 40% of the population is in Europe, 35% in sub-Saharan Africa, 15% in North Africa and the Middle East, 8% in the Americas. French is the fourth-most widely spoken mother tongue in the European Union, 1/5 of Europeans who do not have French as a mother tongue speak French as a second language. As a result of French and Belgian colonialism from the 17th and 18th century onward, French was introduced to new territories in the Americas, Africa, most second-language speakers reside in Francophone Africa, in particular Gabon, Algeria, Mauritius, Senegal and Ivory Coast. In 2015, French was estimated to have 77 to 110 million native speakers, approximately 274 million people are able to speak the language. The Organisation internationale de la Francophonie estimates 700 million by 2050, in 2011, Bloomberg Businessweek ranked French the third most useful language for business, after English and Standard Mandarin Chinese. Under the Constitution of France, French has been the language of the Republic since 1992. France mandates the use of French in official government publications, public education except in specific cases, French is one of the four official languages of Switzerland and is spoken in the western part of Switzerland called Romandie, of which Geneva is the largest city. French is the language of about 23% of the Swiss population. French is also a language of Luxembourg, Monaco, and Aosta Valley, while French dialects remain spoken by minorities on the Channel Islands. A plurality of the worlds French-speaking population lives in Africa and this number does not include the people living in non-Francophone African countries who have learned French as a foreign language. Due to the rise of French in Africa, the total French-speaking population worldwide is expected to reach 700 million people in 2050, French is the fastest growing language on the continent. French is mostly a language in Africa, but it has become a first language in some urban areas, such as the region of Abidjan, Ivory Coast and in Libreville. There is not a single African French, but multiple forms that diverged through contact with various indigenous African languages, sub-Saharan Africa is the region where the French language is most likely to expand, because of the expansion of education and rapid population growth
9.
Photogravure
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The earliest forms of photogravure were developed by two original pioneers of photography itself, first Nicéphore Niépce in France in the 1820s, and later Henry Fox Talbot in England. Niépce was seeking a means to create images on plates that could then be etched and used to make prints on paper with a traditional printing press. Niépces early images were among the first photographs, pre-dating daguerreotypes, Talbot, inventor of the calotype paper negative process, wanted to make paper prints that would not fade. He worked on his process in the 1850s and patented it in 1852 and 1858. Photogravure in its form was developed in 1878 by Czech painter Karel Klíč. This process, the one still in use today, is called the Talbot-Klič process, because of its high quality and richness, photogravure was used for both original fine art prints and for photo-reproduction of works from other media such as paintings. In France the correct term for photogravure is héliogravure, while the French term photogravure refers to any photo-based etching technique, Photogravure registers a wide variety of tones, through the transfer of etching ink from an etched copper plate to special dampened paper run through an etching press. The unique tonal range comes from photogravures variable depth of etch, that is, Photogravure practitioners such as Peter Henry Emerson and others brought the art to a high standard in the late 19th century. This continued with the work of Alfred Stieglitz in the early 20th century and this publication also featured the photogravures of Alvin Langdon Coburn who was a fine gravure printer and envisioned his photographic work as gravures rather than other photo-based processes. The speed and convenience of silver-gelatin photography eventually displaced photogravure which fell into disuse after the Edward S. Curtis gravures in the 1920s. One of the last major portfolios of fine art photogravures was Paul Strands Photographs from Mexico from 1940, many years later, photogravure has experienced a revival in the hands of Aperture and Jon Goodman, who studied it in Europe. Photogravure is now practiced in several dozen workshops around the world. Photogravure plates go through several stages, First, a continuous tone film positive is made from the original photographic negative. A smaller negative can be enlarged onto a sheet of film, the second stage is to sensitize a sheet of pigmented gelatin tissue by immersion into a 3. 5% solution of potassium dichromate for 3 minutes. Once dried against a Plexiglas surface, it is ready for the next stage, the third stage is to expose the film positive to the sensitized gravure tissue. The positive is placed on top of the sheet of pigmented gelatin tissue. The sandwich is then exposed to ultraviolet light, the UV light travels through the positive and screen in succession, each time hardening the gelatin in proportion to the degree of light exposed to it. The fourth stage is to adhere the exposed tissue to the copper plate, the gelatin tissue is adhered or laid down onto the highly polished copper plate under a layer of cool water
10.
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
11.
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
12.
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
13.
Black and white
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Black and white, often abbreviated B/W or B&W, and hyphenated black-and-white when used as an adjective, is any of several monochrome forms in visual arts. Black-and-white images are not usually starkly contrasted black and white and they combine black and white in a continuum producing a range of shades of gray. Even when most studios had the capability to make color films they were not heavily utilized as using the Technicolor process was expensive, 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. Television, Television program was first transmitted in black-and-white, scottish inventor John Logie Baird demonstrated the worlds first color television transmission on July 3,1928 using a mechanical process. Some color broadcasts in the US began in the 1950s, with color becoming common in industrialized nations during the late 1960s. In the United States, the Federal Communications Commission settled on a color NTSC standard in 1953, color television became more widespread in the U. S. between 1963 and 1967, when the CBS and ABC networks joined NBC in broadcasting full color schedules. Canada began airing color television in 1966 while the United Kingdom began to use a different color system from July 1967 known as PAL. The Republic Of Ireland followed in 1970, in China, black and white television sets were the norm until as late as the 1990s, color TVs not outselling them until about 1989. While seldom used now, many consumer camcorders have the ability to record in black-and-white. Photography, Photographs were either black-and-white or shades of sepia, color photography was originally rare and expensive and again often containing inaccurate hues. Color photography became more common from the mid-20th century, Today, black-and-white is a niche market for photographers who use the medium for artistic purposes. This can take the form of film or digital conversion to grayscale. For amateur use certain companies such as Kodak manufactured black-and-white disposable cameras until 2009, also, certain films are produced today which give black-and-white images using the ubiquitous C41 color process. Printing press, Most American newspapers were black-and-white until the early 1980s, The New York Times, some claim that USA Today was the major impetus for the change to color. In the UK, color was only introduced from the mid-1980s. Even today, many newspapers restrict color photographs to the front, similarly, daily comic strips in newspapers were traditionally black-and-white with color reserved for Sunday strips. Sometimes color is reserved for the cover, magazines such as Jet magazine were either all or mostly black-and-white until the end of the 2000s when it became all-color. Manga are typically published in black-and-white although now it is part of its image, many school yearbooks are still entirely or mostly in black-and-white
14.
Chromatic aberration
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In optics, chromatic aberration is an effect resulting from dispersion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have different refractive indices for different wavelengths of light, the refractive index of transparent materials decreases with increasing wavelength in degrees unique to each. Since the focal length f of a lens is dependent on the index n. There are two types of aberration, axial, and transverse. Axial aberration occurs when different wavelengths of light are focused at different distances from the lens, transverse aberration occurs when different wavelengths are focused at different positions in the focal plane. The acronym LCA is used, but ambiguous, and may refer to either longitudinal or lateral CA, for clarity and these two types have different characteristics, and may occur together. Axial CA occurs throughout the image and is specified by optical engineers, optometrists, and vision scientists in the unit of focus known widely as diopters, transverse CA does not occur in the center, and increases towards the edge, but is not affected by stopping down. In the earliest uses of lenses, chromatic aberration was reduced by increasing the length of the lens where possible. For example, this could result in extremely long telescopes such as the very long aerial telescopes of the 17th century, isaac Newtons theories about white light being composed of a spectrum of colors led him to the conclusion that uneven refraction of light caused chromatic aberration. There exists a point called the circle of least confusion, where chromatic aberration can be minimized and it can be further minimized by using an achromatic lens or achromat, in which materials with differing dispersion are assembled together to form a compound lens. The most common type is a doublet, with elements made of crown. This reduces the amount of chromatic aberration over a range of wavelengths. By combining more than two lenses of different composition, the degree of correction can be increased, as seen in an apochromatic lens or apochromat. Similarly, the benefit of apochromats is not simply that they focus 3 wavelengths sharply, many types of glass have been developed to reduce chromatic aberration. These are low dispersion glass, most notably, glasses containing fluorite and these hybridized glasses have a very low level of optical dispersion, only two compiled lenses made of these substances can yield a high level of correction. The use of achromats was an important step in the development of the optical microscope, an alternative to achromatic doublets is the use of diffractive optical elements. Diffractive optical elements are able to generate arbitrary complex wave fronts from a sample of material which is essentially flat. Diffractive optical elements have negative characteristics, complementary to the positive Abbe numbers of optical glasses
15.
Circle of confusion
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In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, in photography, the circle of confusion is used to determine the depth of field, the part of an image that is acceptably sharp. A standard value of CoC is often associated with image format, but the most appropriate value depends on visual acuity, viewing conditions. Usages in context include maximum permissible circle of confusion, circle of confusion diameter limit, real lenses do not focus all rays perfectly, so that even at best focus, a point is imaged as a spot rather than a point. The smallest such spot that a lens can produce is often referred to as the circle of least confusion, two important uses of this term and concept need to be distinguished, For describing the largest blur spot that is indistinguishable from a point. A lens can precisely focus objects at one distance, objects at other distances are defocused. Defocused object points are imaged as blur spots rather than points, the greater the distance an object is from the plane of focus, such a blur spot has the same shape as the lens aperture, but for simplicity, is usually treated as if it were circular. In practice, objects at different distances from the camera can still appear sharp. The common criterion for “acceptable sharpness” in the image is that the blur spot be indistinguishable from a point. For describing the blur spot achieved by a lens, at its best focus or more generally, the term circle of confusion is applied more generally, to the size of the out-of-focus spot to which a lens images an object point. In idealized ray optics, where rays are assumed to converge to a point when perfectly focused, a more general blur spot has soft edges due to diffraction and aberrations, and may be non-circular due to the aperture shape. Therefore, the concept needs to be carefully defined in order to be meaningful. Suitable definitions often use the concept of encircled energy, the fraction of the optical energy of the spot that is within the specified diameter. Values of the fraction vary with application, in photography, the circle of confusion diameter limit for the final image is often defined as the largest blur spot that will still be perceived by the human eye as a point. Conventions in terms of the measure are also commonly used. The DoF computed using these conventions will need to be adjusted if the image is cropped before enlarging to the final image size, or if the size. Using the “Zeiss formula”, the circle of confusion is sometimes calculated as d/1730 where d is the measure of the original image. For full-frame 35 mm format this comes out to be 0.025 mm, a more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm format, which corresponds to resolving 5 lines per millimeter on a print of 30 cm diagonal
16.
Color balance
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In photography and image processing, color balance is the global adjustment of the intensities of the colors. An important goal of this adjustment is to specific colors – particularly neutral colors – correctly. Hence, the method is sometimes called gray balance, neutral balance. Color balance changes the mixture of colors in an image and is used for color correction. Generalized versions of color balance are used to correct colors other than neutrals or to change them for effect. Image data acquired by sensors – either film or electronic image sensors – must be transformed from the values to new values that are appropriate for color reproduction or display. In film photography, color balance is achieved by using color correction filters over the lights or on the camera lens. It is particularly important that neutral colors in a scene appear neutral in the reproduction, most digital cameras have means to select color correction based on the type of scene lighting, using either manual lighting selection, automatic white balance, or custom white balance. The algorithms for these processes perform generalized chromatic adaptation, many methods exist for color balancing. Setting a button on a camera is a way for the user to indicate to the processor the nature of the scene lighting, another option on some cameras is a button which one may press when the camera is pointed at a gray card or other neutral colored object. This captures an image of the ambient light, which enables a digital camera to set the color balance for that light. There is a literature on how one might estimate the ambient lighting from the camera data. A variety of algorithms have been proposed, and the quality of these has been debated, a few examples and examination of the references therein will lead the reader to many others. Examples are Retinex, a neural network or a Bayesian method. Color balancing an image not only the neutrals, but other colors as well. An image that is not color balanced is said to have a color cast, Color balancing may be thought in terms of removing this color cast. Color balance is related to color constancy. Algorithms and techniques used to color constancy are frequently used for color balancing
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Color temperature
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The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable color to that of the light source. Color temperature is a characteristic of light that has important applications in lighting, photography, videography, publishing, manufacturing, astrophysics, horticulture. Color temperature is conventionally expressed in kelvins, using the symbol K, Color temperatures over 5000 K are called cool colors, while lower color temperatures are called warm colors. The fact that warm lighting in this sense actually has a color temperature often leads to confusion. The color temperature of the radiation emitted from an ideal black body is defined as its surface temperature in kelvins. This permits the definition of a standard by which light sources are compared, to the extent that a hot surface emits thermal radiation but is not an ideal black-body radiator, the color temperature of the light is not the actual temperature of the surface. An incandescent lamps light is thermal radiation, and the bulb approximates an ideal black-body radiator and this means that the emitted radiation does not follow the form of a black-body spectrum. These sources are assigned what is known as a color temperature. CCT is the temperature of a black-body radiator which to human color perception most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, the Sun closely approximates a black-body radiator. The effective temperature, defined by the radiative power per square unit, is about 5780 K. The color temperature of sunlight above the atmosphere is about 5900 K, as the Sun crosses the sky, it may appear to be red, orange, yellow or white depending on its position. The changing color of the Sun over the course of the day is mainly a result of scattering of light and is not due to changes in black-body radiation. The blue color of the sky is caused by Rayleigh scattering of the sunlight from the atmosphere, some early morning and evening light has a lower color temperature due to increased low-wavelength light scattering by the Tyndall effect. Daylight has a similar to that of a black body with a correlated color temperature of 6500 K or 5500 K. For colors based on theory, blue occurs at higher temperatures. This is the opposite of the cultural associations attributed to colors, in red is hot. For lighting building interiors, it is important to take into account the color temperature of illumination
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Depth of field
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In some cases, it may be desirable to have the entire image sharp, and a large DOF is appropriate. In other cases, a small DOF may be more effective, in cinematography, a large DOF is often called deep focus, and a small DOF is often called shallow focus. Precise focus is possible at one distance, at that distance. At any other distance, a point object is defocused, and will produce a blur spot shaped like the aperture, when this circular spot is sufficiently small, it is indistinguishable from a point, and appears to be in focus, it is rendered as acceptably sharp. The acceptable circle of confusion is influenced by visual acuity, viewing conditions, the increase of the circle diameter with defocus is gradual, so the limits of depth of field are not hard boundaries between sharp and unsharp. For 35 mm motion pictures, the area on the film is roughly 22 mm by 16 mm. The limit of tolerable error was traditionally set at 0.05 mm diameter, while for 16 mm film, where the size is half as large. More modern practice for 35 mm productions set the circle of confusion limit at 0.025 mm, for full-frame 35mm still photography, the circle of confusion is usually chosen to be about 1/30 mm. Many sources propose CoC limits as a fraction of the film format diagonal, the three formats above at fraction 1/1500 would use 0.029,0.056, and 0.017 mm. Traditional depth-of-field formulas and tables assume equal circles of confusion for near and far objects, the loss of detail in distant objects may be particularly noticeable with extreme enlargements. Achieving this additional sharpness in distant objects usually requires focusing beyond the hyperfocal distance, with this approach, foreground objects cannot always be made perfectly sharp, but the loss of sharpness in near objects may be acceptable if recognizability of distant objects is paramount. Other authors have taken the position, maintaining that slight unsharpness in foreground objects is usually more disturbing than slight unsharpness in distant parts of a scene. The combination of length, subject distance, and format size defines magnification at the film / sensor plane. DOF is determined by subject magnification at the film / sensor plane, for a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF, decreasing magnification increases DOF. For a given magnification, increasing the f-number increases the DOF. If the original image is enlarged to make the final image, when focus is set to the hyperfocal distance, the DOF extends from half the hyperfocal distance to infinity, and the DOF is the largest possible for a given f-number. The comparative DOFs of two different format sizes depend on the conditions of the comparison, the DOF for the smaller format can be either more than or less than that for the larger format. In the discussion that follows, it is assumed that the images from both formats are the same size, are viewed from the same distance, and are judged with the same circle of confusion criterion
19.
Exposure (photography)
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In photography, exposure is the amount of light per unit area reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value, in photographic jargon, an exposure generally refers to a single shutter cycle. For the same speed, the accumulated photometric exposure should be similar in both cases. A photograph may be described as underexposed when it has a loss of detail, that is. As the adjacent image shows, these terms are technical ones, there are three types of settings, manual, automatic and exposure compensation. Radiant exposure of a surface, denoted He and measured in J/m2, is given by H e = E e t, where Ee is the irradiance of the surface, measured in W/m2, t is the exposure duration, measured in s. Luminous exposure of a surface, denoted Hv and measured in lx⋅s, is given by H v = E v t, many photographic materials are also sensitive to invisible light, which can be a nuisance, or a benefit. The use of units is appropriate to characterize such sensitivity to invisible light. In sensitometric data, such as curves, the log exposure is conventionally expressed as log10. Photographers more familiar with base-2 logarithmic scales can convert using log2 ≈3.32 log10, correct exposure may be defined as an exposure that achieves the effect the photographer intended. A more technical approach recognises that a film has a physically limited useful exposure range. If, for any part of the photograph, the exposure is outside this range. In a very simple model, for example, out-of-range values would be recorded as black or white rather than the precisely graduated shades of colour and this ensures that no significant information is lost during capture. However, it is much easier to discard recorded information during post processing than to try to re-create unrecorded information. In a scene with strong or harsh lighting, the ratio between highlight and shadow luminance values may well be larger than the ratio between the maximum and minimum useful exposure values. A photograph may be described as underexposed when it has a loss of detail, that is. In manual mode, the photographer adjusts the lens aperture and/or shutter speed to achieve the desired exposure, manual exposure calculations may be based on some method of light metering with a working knowledge of exposure values, the APEX system and/or the Zone System. A camera in automatic exposure mode automatically calculates and adjusts exposure settings to match the subjects mid-tone to the mid-tone of the photograph, for most cameras this means using an on-board TTL exposure meter
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Exposure compensation
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Factors considered may include unusual lighting distribution, variations within a camera system, filters, non-standard processing, or intended underexposure or overexposure. Cinematographers may also apply exposure compensation for changes in angle or film speed. Most DSLR cameras have a display whereby the photographer can set the camera to either over or under expose the subject by up to three f-stops in 1/3rd stop intervals. Each number on the scale represents one f-stop, decreasing the exposure by one f-stop will halve the amount of light reaching the sensor, the dots in between the numbers represent 1/3rd of an f-stop. In photography, some cameras include exposure compensation as a feature to allow the user to adjust the automatically calculated exposure, camera exposure compensation is commonly stated in terms of EV units,1 EV is equal to one exposure step, corresponding to a doubling of exposure. Exposure can be adjusted by changing either the lens f-number or the exposure time, if the mode is aperture priority, exposure compensation changes the exposure time, if the mode is shutter priority, the f-number is changed. If a flash is being used, some cameras will adjust it as well, the earliest reflected-light exposure meters were wide-angle, averaging types, measuring the average scene luminance. When measuring a scene with atypical distribution of light and dark elements, or an element that is lighter or darker than a middle tone. For example, a scene with predominantly light tones often will be underexposed and that both scenes require the same exposure, regardless of the meter indication, becomes obvious from a scene that includes both a white horse and a black horse. A photographer usually can recognize the difference between a horse and a black horse, a meter usually cannot. When metering a white horse, a photographer can apply exposure compensation so that the horse is rendered as white. Many modern cameras incorporate metering systems that measure scene contrast as well as average luminance, in scenes with very unusual lighting, however, these metering systems sometimes cannot match the judgment of a skilled photographer, so exposure compensation still may be needed. An early application of compensation was the Zone System developed by Ansel Adams. Developed for black-and-white film, the Zone System divided luminance into 11 zones, with Zone 0 representing pure black, the meter indication would place whatever was metered on Zone V, a medium gray. The meter indication, however, remains Zone V, the Zone System is a very specialized form of exposure compensation, and is used most effectively when metering individual scene elements, such as a sunlit rock or the bark of a tree in shade. Many cameras incorporate narrow-angle spot meters to facilitate such measurements, because of the limited tonal range, an exposure compensation range of ±2 EV is often sufficient for using the Zone System with color film and digital sensors. Exposure value Exposure index Light meter Zone System Exposure bracketing Auto Exposure Bracketing
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Exposure value
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In photography, exposure value is a number that represents a combination of a cameras shutter speed and f-number, such that all combinations that yield the same exposure have the same EV. Exposure value is used to indicate an interval on the photographic exposure scale, with a difference of 1 EV corresponding to a standard power-of-2 exposure step. The EV concept was developed by the German shutter manufacturer Friedrich Deckel in the 1950s and its intent was to simplify choosing among equivalent camera exposure settings by replacing combinations of shutter speed and f-number with a single number. This was especially helpful to beginners with limited understanding of the shutter speed and aperture. The concept became known as the Light Value System in Europe, the proper EV was determined by the scene luminance and film speed, it was intended that the system also include adjustment for filters, exposure compensation, and other variables. With all of elements included, the camera would be set by transferring the single number thus determined. Exposure value has been indicated in various ways, although all camera settings with the same EV nominally give the same exposure, they do not necessarily give the same picture. The f-number determines the depth of field, and the shutter speed determines the amount of motion blur, if the EV is known, it can be used to select combinations of exposure time and f-number, as shown in Table 1. Greater exposure values are appropriate for photography in more brightly lit situations, to avoid confusion, some authors have used camera exposure to refer to combinations of camera settings. The 1964 ASA standard for automatic exposure controls for cameras, ASA PH2. 15-1964, took the same approach, common practice among photographers is nonetheless to use “exposure” to refer to camera settings as well as to photometric exposure. If, for example, the f-number is changed, an equivalent exposure time can be determined from t 2 t 1 = N22 N12. Performing this calculation mentally is tedious for most photographers, but the equation is solved with a calculator dial on an exposure meter or a similar dial on a standalone calculator. If the camera controls have detents, constant exposure can be maintained by counting the steps as one control is adjusted, the ratio t/N2 could be used to represent equivalent combinations of exposure time and f-number in a single value. But for many such combinations used in photography, the ratio gives a fractional value with a large denominator. For example, beginning with 1 s and f/1, decreasing exposure gives the simple sequence 0,1,2,3, the last two values shown frequently apply when using ISO100 speed imaging media in outdoor photography. Current cameras do not allow direct setting of EV, and cameras with automatic exposure control generally obviate the need for it, EV can nonetheless be helpful when used to transfer recommended exposure settings from an exposure meter to an exposure calculator. Used as an indicator of camera settings, EV corresponds to actual combinations of shutter speed, when the actual EV matches that recommended by the light level and the ISO speed, these settings should result in the “correct” exposure. If the common value of K =12.5 is used, at EV =15 the luminance is 380 cd/ft2 or 4096 cd/m2
22.
F-number
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The f-number of an optical system such as a camera lens is the ratio of the systems focal length to the diameter of the entrance pupil. It is a number that is a quantitative measure of lens speed. It is also known as the ratio, f-ratio, f-stop. The f-number is commonly indicated using a hooked f with the format f/N, the f-number N or f# is given by, N = f D where f is the focal length, and D is the diameter of the entrance pupil. It is customary to write f-numbers preceded by f/, which forms a mathematical expression of the pupil diameter in terms of f and N. Ignoring differences in light transmission efficiency, a lens with a greater f-number projects darker images, the brightness of the projected image relative to the brightness of the scene in the lenss field of view decreases with the square of the f-number. Doubling the f-number decreases the brightness by a factor of four. To maintain the same photographic exposure when doubling the f-number, the time would need to be four times as long. Most lenses have a diaphragm, which changes the size of the aperture stop. The entrance pupil diameter is not necessarily equal to the aperture stop diameter, a 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A200 mm focal length f/4 lens has a pupil diameter of 50 mm. The 200 mm lenss entrance pupil has four times the area of the 100 mm lenss entrance pupil, a T-stop is an f-number adjusted to account for light transmission efficiency. The word stop is sometimes confusing due to its multiple meanings, a stop can be a physical object, an opaque part of an optical system that blocks certain rays. In photography, stops are also a used to quantify ratios of light or exposure. The one-stop unit is known as the EV unit. On a camera, the setting is traditionally adjusted in discrete steps. Each stop is marked with its corresponding f-number, and represents a halving of the light intensity from the previous stop. This corresponds to a decrease of the pupil and aperture diameters by a factor of 1/2 or about 0.7071, each element in the sequence is one stop lower than the element to its left, and one stop higher than the element to its right
23.
Large format
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Large format refers to any imaging format of 4×5 inches or larger. Large format is larger than medium format, the 6×6 cm or 6×9 cm size of Hasselblad, Rollei, Kowa, and Pentax cameras, and much larger than the 24×36 mm frame of 35 mm format. The main advantage of large format, film or digital, is higher resolution at the pixel pitch. A 4×5 inch image has about 16 times the area, and thus 16× the total resolution, of a 35 mm frame. Large format cameras were some of the earliest photographic devices, and before enlargers were common, it was normal to just make 1,1 contact prints from a 4×5, 5×7, or 8×10-inch negative. The most common format is 4×5 inches, which was the size common cameras used in the 1930s-1950s, like the Graflex Speed Graphic and Crown Graphic. Above 8×10 inches, the formats are referred to as Ultra Large Format and may be 11×14, 16×20, or 20×24 inches or as large as film, plates. Many large formats are horizontal cameras designed to make big negatives for contact printing onto press-printing plates, the Polaroid 20×24 camera is one of the largest format instant cameras in common usage and can be hired from Polaroid agents in various countries. Many well-known photographers have used the 235 pounds, wheeled-chassis Polaroid, architectural and close-up photographers in particular benefit greatly from this ability. These allow the front and back of the camera to be shifted up/down and left/right, a number of actions need to be taken to use a typical large format camera, resulting in a slower, often more contemplative, photographic style. A tripod is used for view camera work, but some models are designed for hand-held use. These technical cameras have separate viewfinders and rangefinders for faster handling, in general large format camera use, the scene is composed on the cameras ground glass, and then a film holder is fitted to the camera back prior to exposure. Failure to Polaroid an exposure risks discovery later, at the time of film development, the 4×5 inch sheet film format was very convenient for press photography since it allowed for direct contact printing on the printing plate, hence it was widely used in press cameras. This was done well into the 1940s and 1950s, even with the advent of more convenient, the 35 mm and medium format SLR which appeared in the mid-1950s were soon adopted by press photographers. Large format photography is not limited to film, large digital camera backs are available to fit large format cameras and these are either medium-format digital backs adapted to fit large format cameras, step and repeat Multishot systems, or scanning backs. Scanning backs can take seconds or even minutes to capture an image. When using a Sinar Macroscan unit and 54H data files, over 1 gigabyte of data is produced, high quality fine art prints can be made at sizes in the range of 40x50 from a 4×5 original, and well beyond that for larger negatives. The Library of Congress uses various large format digital scans for American Memories in the current JPEG2000 format, and the older MrSID, JPEG, and TIFF formats
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Medium format (film)
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Medium format has traditionally referred to a film format in still photography and the related cameras and equipment that use film. Generally, the term applies to film and digital cameras that record images on media larger than 24 by 36 mm, but smaller than 4 by 5 inches. In digital photography, medium format refers either to cameras adapted from medium-format film photography uses, or to cameras making use of sensors larger than that of a 35 mm film frame. As of 2013, medium-format digital photography sensors were available in sizes of up to 40.3 by 53.7 mm, sensors used in special applications such as spy satellites can be even larger, but are not necessarily described as medium-format equipment. In digital, medium format is an expensive option, with typical brand new all-digital medium-format cameras retailing for $10,000 to $32,000 in 2008. While at one time or another a variety of medium-format film sizes were produced, other sizes are mainly produced for use in antique cameras, and many people assume 120/220 film when the term medium format is used. The general rule with consumer cameras—as opposed to specialized industrial, scientific, and military equipment—is the more cameras sold, medium-format cameras made since the 1950s are generally less automated than smaller cameras made at the same time, having high image quality as their primary advantage. For example, autofocus became available in consumer 35 mm cameras in 1977, but did not reach medium format until the late 1990s, and has never been available in a consumer large format camera. The main benefit of medium-format photography is that, because of the size of the film or digital sensor. This allows for enlargements and smooth gradation without the grain or blur that would characterize similarly enlarged images produced from smaller film formats. The larger size of the film allows for better control of the depth of field. Cameras with a bellows typically support tilt and shift of the lens, together with 1,1 focusing, this permits landscape photography with an extremely large depth of field — from closest foreground to the far horizon — to be achieved. Compared to 35 mm, the drawbacks are accessibility and price. Also, medium-format cameras tend to be bulkier than their 35mm counterpart, medium-format film is usually roll film, typically allowing 8 to 32 exposures on one roll of film before reloading is needed. This is less convenient than 35 mm cartridges, which typically take 12 to 36 pictures on one roll, some companies had bulk film backs that used 70mm double-perforated that allowed up to 75 feet of film to be loaded at one time. While rolls of large format film were produced at one time, their use was specialized, medium-format sheet film was produced for some cameras, but these cameras tend to be smaller, lighter, and easier to use than large format gear. Sheet film was never used in cameras smaller than medium format. Film cost per exposure is related to the amount of film used, thus, the larger the film size
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Film speed
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Film speed is the measure of a photographic films sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A closely related ISO system is used to measure the sensitivity of digital imaging systems, highly sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality, in short, the higher the sensitivity, the grainier the image will be. Ultimately sensitivity is limited by the efficiency of the film or sensor. The speed of the emulsion was then expressed in degrees Warnerke corresponding with the last number visible on the plate after development. Each number represented an increase of 1/3 in speed, typical speeds were between 10° and 25° Warnerke at the time. The concept, however, was built upon in 1900 by Henry Chapman Jones in the development of his plate tester. In their system, speed numbers were inversely proportional to the exposure required, for example, an emulsion rated at 250 H&D would require ten times the exposure of an emulsion rated at 2500 H&D. The methods to determine the sensitivity were later modified in 1925, the H&D system was officially accepted as a standard in the former Soviet Union from 1928 until September 1951, when it was superseded by GOST 2817-50. The Scheinergrade system was devised by the German astronomer Julius Scheiner in 1894 originally as a method of comparing the speeds of plates used for astronomical photography, Scheiners system rated the speed of a plate by the least exposure to produce a visible darkening upon development. ≈2 The system was extended to cover larger ranges and some of its practical shortcomings were addressed by the Austrian scientist Josef Maria Eder. Scheiners system was abandoned in Germany, when the standardized DIN system was introduced in 1934. In various forms, it continued to be in use in other countries for some time. The DIN system, officially DIN standard 4512 by Deutsches Institut für Normung, was published in January 1934, International Congress of Photography held in Dresden from August 3 to 8,1931. The DIN system was inspired by Scheiners system, but the sensitivities were represented as the base 10 logarithm of the sensitivity multiplied by 10, similar to decibels. Thus an increase of 20° represented an increase in sensitivity. ≈3 /10 As in the Scheiner system, speeds were expressed in degrees, originally the sensitivity was written as a fraction with tenths, where the resultant value 1.8 represented the relative base 10 logarithm of the speed. Tenths were later abandoned with DIN4512, 1957-11, and the example above would be written as 18° DIN, the degree symbol was finally dropped with DIN4512, 1961-10
26.
Focal length
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The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a focal length has greater optical power than one with a long focal length. For a thin lens in air, the length is the distance from the center of the lens to the principal foci of the lens. For a converging lens, the length is positive, and is the distance at which a beam of collimated light will be focused to a single spot. For a diverging lens, the length is negative, and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens. The focal length of a lens can be easily measured by using it to form an image of a distant light source on a screen. The lens is moved until an image is formed on the screen. In this case 1/u is negligible, and the length is then given by f ≈ v. Back focal length or back focal distance is the distance from the vertex of the last optical surface of the system to the focal point. For an optical system in air, the focal length gives the distance from the front. If the surrounding medium is not air, then the distance is multiplied by the index of the medium. Some authors call these distances the front/rear focal lengths, distinguishing them from the front/rear focal distances, defined above. In general, the length or EFL is the value that describes the ability of the optical system to focus light. The other parameters are used in determining where an image will be formed for an object position. The quantity 1/f is also known as the power of the lens. The corresponding front focal distance is, FFD = f, in the sign convention used here, the value of R1 will be positive if the first lens surface is convex, and negative if it is concave. The value of R2 is negative if the surface is convex
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Hyperfocal distance
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In optics and photography, hyperfocal distance is a distance beyond which all objects can be brought into an acceptable focus. When the lens is focused at this distance, all objects at distances from half of the distance out to infinity will be acceptably sharp. Definition 2, The hyperfocal distance is the distance beyond which all objects are acceptably sharp, the distinction between the two meanings is rarely made, since they have almost identical values. The value computed according to the first definition exceeds that from the second by just one focal length, as the hyperfocal distance is the focus distance giving the maximum depth of field, it is the most desirable distance to set the focus of a fixed-focus camera. The hyperfocal distance is entirely dependent upon what level of sharpness is considered to be acceptable, the criterion for the desired acceptable sharpness is specified through the circle of confusion diameter limit. This criterion is the largest acceptable spot size diameter that a point is allowed to spread out to on the imaging medium. For practical purposes, there is difference between the first and second definitions. The following derivations refer to the accompanying figures, for clarity, half the aperture and circle of confusion are indicated. An object at distance H forms an image at distance x. Here, objects at infinity have images with a circle of confusion indicated by the ellipse where the upper red ray through the focal point intersects the blue line. Objects at infinity form sharp images at the length f. Here, an object at H forms an image with a circle of confusion indicated by the ellipse where the lower red ray converging to its sharp image intersects the blue line. With the formula for the Definition 2, the result is 10417 mm and this continues on through all successive 1/x values of the hyperfocal distance. Piper calls this phenomenon consecutive depths of field and shows how to test the idea easily and this is also among the earliest of publications to use the word hyperfocal. The figure on the right illustrates this phenomenon, the concepts of the two definitions of hyperfocal distance have a long history, tied up with the terminology for depth of field, depth of focus, circle of confusion, etc. Here are some selected early quotations and interpretations on the topic, thomas Sutton and George Dawson define focal range for what we now call hyperfocal distance, Focal Range. In every lens there is, corresponding to a given apertal ratio, for instance, in a single view lens of 6 inch focus, with a 1/4 in. Stop, all situated at distances lying between 20 feet from the lens and an infinite distance from it are in equally good focus
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Metering mode
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In photography, the metering mode refers to the way in which a camera determines the exposure. Cameras generally allow the user to select between spot, center-weighted average, or multi-zone metering modes, various metering modes are provided to allow the user to select the most appropriate one for use in a variety of lighting conditions. With spot metering, the camera will only measure a small area of the scene. This will by default be the centre of the scene. The user can select a different off-centre spot, or to recompose by moving the camera after metering. The first spot meter was built by Arthur James Dalladay, editor of The British Journal of Photography in about 1935, a few models support a Multi-Spot mode which allows multiple spot meter readings to be taken of a scene that are averaged. Some cameras, the OM-4 and T90 included, also support metering of highlight, spot metering is very accurate and is not influenced by other areas in the frame. It is commonly used to very high contrast scenes. The area around the back and hairline will then become over-exposed, spot metering is a method upon which the Zone System depends. In many cases the camera will over or underexpose, when using the spot mode, modern cameras tend to find the correct exposure precisely. In complex light situations though, professional photographers tend to switch to manual mode, another example of spot metering usage would be when photographing the moon. Due to the dark nature of the scene, other metering methods tend to overexpose the moon. Spot metering will allow for more detail to be out in the moon while underexposing the rest of the scene. More commonly, spot metering is used in photography, where the brightly lit actors stand before a dark or even black curtain or scrim. Spot metering only considers the actors in this case, while ignoring the overall darkness of the scene, in this system, the meter concentrates between 60 to 80 percent of the sensitivity towards the central part of the viewfinder. The balance is then feathered out towards the edges, some cameras will allow the user to adjust the weight/balance of the central portion to the peripheral one. When moving the point off center the camera will proceed as above. Although promoted as a feature, center-weighted metering was originally a consequence of the meter cell reading from the screen of SLR cameras
29.
Orb (optics)
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In photography, an orb is a typically circular artifact on an image, created as a result of flash photography illuminating a mote of dust or other particle. Orbs are especially common with modern compact and ultra-compact digital cameras, orbs are also sometimes called backscatter, orb backscatter, or near-camera reflection. Some orbs appear with trails indicating motion, orbs are captured during low-light instances where the cameras flash is used. Cases include night or underwater photography, or where a light source is near the camera. Light appears much brighter very near the source due to the inverse-square law, the orb artifact can result from retroreflection of light off solid particles, such as dust or pollen, or liquid particles, especially rain. They can also be caused by foreign material within the camera lens, the image artifacts usually appear as either white or semi-transparent circles, though may also occur with whole or partial color spectra, purple fringing or other chromatic aberration. With rain droplets, an image may capture light passing through the droplet creating a rainbow effect. In underwater conditions, particles such as sand or small sea life close to the lens, invisible to the diver, Orb Bokeh Digital artifact Rod Rolling shutter Will-o-the-wisp The science of orb photos, by Mark Kimura The Orb Video Archive
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Perspective distortion (photography)
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Related to this concept is axial magnification -- the perceived depth of objects at a given magnification. Extension or wide-angle distortion can be seen in shot from close using a wide-angle lens. Objects close to the lens appear abnormally large relative to distant objects. Compression, long-lens, or telephoto distortion can be seen in shot from a distance using a long focus lens or the more common telephoto sub-type. However, since wide-angle lenses have a field of view, they are generally used from closer. However, crops of these three images with the coverage will yield the same perspective distortion – the nose will look the same in all three. Outside of photography, extension distortion is familiar to many through side-view mirrors and peepholes, though these often use a fisheye lens, consider an idealised Gaussian optical system. For most purposes, we can assume the image space and the space are in the same medium. The opposite-- increased axial magnification -- happens with shorter focal lengths while moving the camera/lens towards the object, when photographs are viewed at the ordinary viewing distance, the angle of view at which the image is captured accounts completely for the appearance of perspective distortion. The general assumption that undoctored photos cannot distort a scene is incorrect, Perspective distortion is particularly noticeable in portraits taken with wide-angle lenses at short camera-to-subject distances. They generally give an unpleasant impression, making the nose appear too large with respect to the rest of the face, framing the same subject identically while using a moderate telephoto or long focus lens flattens the image to a more flattering perspective. It is for this reason that, for a 35 mm camera and it does however make difference, whether the photograph is taken landscape or portrait. A50 mm lens is suitable for photographing people when the orientation is landscape, conversely, using lenses with much longer focal lengths for portraits results in more extreme flattening of facial features, which also may be objectionable to the viewer. Photographs are ordinarily viewed at an approximately equal to their diagonal. When viewed at this distance, the effects created by the angle of view of the capture are apparent. However, theoretically, if one views pictures exhibiting extension distortion at a distance, thus widening the angle of view of the presentation. Similarly, viewing pictures exhibiting compression distortion from a distance, thus narrowing the angle of view of the presentation. In both cases, at some distance, the apparent distortion disappears completely
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Photograph
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A photograph or photo is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic medium such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scenes visible wavelengths of light into a reproduction of what the eye would see. The process and practice of creating photographs is called photography, the word photograph was coined in 1839 by Sir John Herschel and is based on the Greek φῶς, meaning light, and γραφή, meaning drawing, writing, together meaning drawing with light. The first permanent photograph, a copy of an engraving, was made in 1822 using the bitumen-based heliography process developed by Nicéphore Niépce. In 1829 Niépce entered into a partnership with Louis Daguerre and the two collaborated to work out a similar but more sensitive and otherwise improved process, after Niépces death in 1833, Daguerre concentrated on silver halide-based alternatives. He named this first practical process for making photographs with a camera the daguerreotype and its existence was announced to the world on 7 January 1839 but working details were not made public until 19 August. Other inventors soon made improvements which reduced the exposure time from a few minutes to a few seconds, making portrait photography truly practical. The daguerreotype had shortcomings, notably the fragility of the image surface. Each was a unique opaque positive that could only be duplicated by copying it with a camera, inventors set about working out improved processes that would be more practical. By the end of the 1850s the daguerreotype had been replaced by the expensive and more easily viewed ambrotype and tintype. The mid-1930s saw the introduction of Kodachrome and Agfacolor Neu, the first easy-to-use color films of the modern multi-layer chromogenic type, the needs of the motion picture industry generated a number of special processes and systems, perhaps the best-known being the now-obsolete three-strip Technicolor process. Non-digital photographs are produced with a chemical process. In the two-step process the film captures a negative image. To produce an image, the negative is most commonly transferred onto photographic paper. Printing the negative onto transparent film stock is used to motion picture films. Alternatively, the film is processed to invert the negative image, such positive images are usually mounted in frames, called slides. Before recent advances in photography, transparencies were widely used by professionals because of their sharpness. Most photographs published in magazines were taken on color transparency film, originally, all photographs were monochromatic or hand-painted in color
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Red-eye effect
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The red-eye effect in photography is the common appearance of red pupils in color photographs of eyes. It occurs when using a photographic flash very close to the camera lens, the effect appears in the eyes of humans, and of animals that have tapetum lucidum. Theatrical followspot operators, positioned nearly coincidentally with a bright light and somewhat distant from the actors. The effect is not visible to the rest of the audience because it is reliant on the small angle between the followspot operator and the light. The camera records this reflected light, the main cause of the red color is the ample amount of blood in the choroid which nourishes the back of the eye and is located behind the retina. The blood in the circulation is far less than in the choroid. The eye contains several photostable pigments that all absorb in the wavelength region. The lens cuts off deep blue and violet light, below 430 nm, melanin, located in the retinal pigment epithelium and the choroid, shows a gradually increasing absorption towards the short wavelengths. But blood is the determinant of the red color, because it is completely transparent at long wavelengths. The amount of red light emerging from the pupil depends on the amount of melanin in the layers behind the retina and this amount varies strongly between individuals. Light skinned people with blue eyes have relatively low melanin in the fundus and thus show a much stronger effect than dark skinned people with brown eyes. The color of the iris itself is of no importance for the red-eye effect. This is obvious because the effect is most apparent when photographing dark adapted subjects. The role of melanin in red-eye effect is demonstrated in animals with heterochromia. The effect is more pronounced in humans and animals with albinism. All forms of albinism involve abnormal production and/or deposition of melanin, similar effects, some related to red-eye effect, are of several kinds, In many flash photographs, even those without perceptible red-eye effect, many animals pupils display eyeshine. Although eyeshine is an effect, animals with blue eyes may display the red-eye effect in addition to eyeshine. A related effect, red reflex, is seen in fundoscopy, here, in photographs recorded with infrared-sensitive passive equipment, the eyes usually appear very bright
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Science of photography
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The science of photography refers to the use of science, such as chemistry and physics, in all aspects of photography. This applies to the camera, its lenses, physical operation of the camera, electronic camera internals, changes to any of these elements are often measured in units known as stops, a stop is equal to a factor of two. The luminance of the scene, as measured on a light meter. The amount of light required for proper exposure depends on the film speed, with either of these changes, the aperture or shutter speed can be adjusted by an equal number of stops to get to a suitable exposure. Light is most easily controlled through the use of the cameras aperture, using faster or slower film is not usually something that can be done quickly, at least using roll film. Large format cameras use individual sheets of film and each sheet could be a different speed, also, if youre using a larger format camera with a polaroid back, you can switch between backs containing different speed polaroids. Digital cameras can easily adjust the speed they are simulating by adjusting the exposure index. For example, starting with an exposure of 1/60 at f/16, the depth-of-field could be made shallower by opening up the aperture to f/4, an increase in exposure of 4 stops. To compensate, the speed would need to be increased as well by 4 stops. Closing down the aperture limits the resolution due to the diffraction limit and this is known as reciprocity failure of the material. A photographic lens is composed of several lens elements, which combine to reduce the effects of chromatic aberration, coma, spherical aberration. A simple example is the three-element Cooke triplet, still in use over a century after it was first designed, using a smaller aperture can reduce most, but not all aberrations. They can also be reduced dramatically by using an aspheric element, fresnel lenses are not used in cameras even though they are extremely light and cheap, because they produce poor image quality. The recently developed Fiber-coupled monocentric lens consists of spheres constructed of concentric shells of different glasses tied to the focal plane by bundles of optical fibers. Monocentric lenses are not used in cameras because the technology was just debuted in October 2013 at the Frontiers in Optics Conference in Orlando. All lens design is a compromise between numerous factors, not excluding cost, zoom lenses involve additional compromises and therefore normally do not match the performance of prime lenses. The range of distances that are nearly in focus is called the depth of field, depth of field generally increases with decreasing aperture diameter. The unfocused blur outside the depth of field is used for artistic effect in photography
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Shutter speed
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The amount of light that reaches the film or image sensor is proportional to the exposure time. 1/500th of a second will let half as much light in as 1/250th, the cameras shutter speed, the lenss aperture, and the scenes luminance together determine the amount of light that reaches the film or sensor. Exposure value is a quantity that accounts for the shutter speed and this will achieve a good exposure when all the details of the scene are legible on the photograph. Too much light let into the results in an overly pale image while too little light will result in an overly dark image. Multiple combinations of speed and f-number can give the same exposure value. According to exposure value formula, doubling the exposure time doubles the amount of light, for example, f/8 lets 4 times more light into the camera as f/16 does. In addition to its effect on exposure, the speed changes the way movement appears in photographs. Very short shutter speeds can be used to freeze fast-moving subjects, very long shutter speeds are used to intentionally blur a moving subject for effect. Short exposure times are called fast, and long exposure times slow. Adjustments to the aperture need to be compensated by changes of the speed to keep the same exposure. The agreed standards for shutter speeds are, With this scale, camera shutters often include one or two other settings for making very long exposures, B keeps the shutter open as long as the shutter release is held. T keeps the open until the shutter release is pressed again. The ability of the photographer to take images without noticeable blurring by camera movement is an important parameter in the choice of the slowest possible speed for a handheld camera. Through practice and special techniques such as bracing the camera, arms, or body to minimize movement, using a monopod or a tripod. If a shutter speed is too slow for hand holding, a support, usually a tripod. Image stabilization on digital cameras or lenses can often permit the use of shutter speeds 3–4 stops slower, Shutter priority refers to a shooting mode used in cameras. It allows the photographer to choose a shutter speed setting and allow the camera to decide the correct aperture and this is sometimes referred to as Shutter Speed Priority Auto Exposure, or TV mode, S mode on Nikons and most other brands. Shutter speed is one of methods used to control the amount of light recorded by the cameras digital sensor or film
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Flash synchronization
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In a camera, flash synchronization is defined as synchronizing the firing of a photographic flash with the opening of the shutter admitting light to photographic film or electronic image sensor. It is often shortened to flash sync or flash synch, in electronic digital cameras, the mechanism is usually a programmable electronic timing circuit, which may, in some cameras, take input from a mechanical shutter contact. The flash is connected electrically to the camera either by a cable with a standardised coaxial PC3.5 mm connector, or via contacts in an accessory mount bracket. X-sync is the simplest to explain and implement, the flash is fired at the instant the shutter is fully open and these sync modes close the contacts a few milliseconds before the shutter is open, to give the flashbulb time to reach peak brightness before exposing the film. Class M bulbs reach their peak illumination at around 20-25 milliseconds after ignition, most standard flash bulbs used M sync. X sync closes the flash contact just as the blades are almost completely open. FP sync was used with FP flash bulbs designed specifically for use with focal-plane shutters, FP bulbs burned close to full brightness for the full X-sync time, exposing the whole frame even at high shutter speeds. The Nikon F offered FP, M, and ME bulb synchronizations, X sync is a mode designed for use with electronic flash. In this mode, the timing of the contacts coincides exactly with the opening of the shutter. Special electronic flash units for focal-plane shutters fire several times as the slit moves across the film, electronic shutters used in some digital cameras do not have this limitation and may allow a very high X-sync speed. Leaf shutters, which are situated within the lens housing, open to expose the entire image at once. The Friedrich Deckel Synchro-Compur leaf shutter of the Braun Paxette Reflex offered V, X, higher sync speeds are useful as they enable the brightness of the background to be controlled while maintaining normal flash exposure in the foreground, for example with a back-lit subject. Today, certain modern xenon flash units have the ability to produce a flash to permit flash synchronization at shorter shutter speeds. Instead of delivering one burst of light, the units deliver several smaller bursts over an interval as short as 1/125 of a second. This allows light to be delivered to the area of the film or image sensor even though the shutter is never fully open at any moment. The downside is that the flash is of less effective intensity since the individual bursts are lower powered than the capability of the flash unit. Wireless remote flash triggers with these features are becoming more common and this mode is called either rear-curtain sync or 2nd-curtain sync. The first camera to implement a flash synchronizer was the Exakta, some synchronization methods employ optical or radio triggering that requires no electrical connection to the camera or main flash unit
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Zone System
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The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer. The technique is based on the late 19th century sensitometry studies of Hurter, the Zone System provides photographers with a systematic method of precisely defining the relationship between the way they visualize the photographic subject and the final results. Although it originated with black-and-white sheet film, the Zone System is also applicable to roll film, an expressive image involves the arrangement and rendering of various scene elements according to the photographer’s desire. Achieving the desired image involves image management and control of image values, the Zone System is concerned with control of image values, ensuring that light and dark values are rendered as desired. Anticipation of the result before making the exposure is known as visualization. Any scene of photographic interest contains elements of different luminance, consequently, the exposure time is the same for all elements, but the image illuminance varies with the luminance of each subject element. Exposure is often determined using an exposure meter. The earliest meters measured overall average luminance, meter calibration was established to give satisfactory exposures for typical outdoor scenes, an averaging meter cannot distinguish between a subject of uniform luminance and one that consists of light and dark elements. When exposure is determined from average luminance measurements, the exposure of any given scene element depends on the relationship of its reflectance to the effective average reflectance. For example, an object of 4% reflectance would be given a different exposure in a scene of 20% effective average reflectance than it would be given in a scene of 12% reflectance. In a sunlit outdoor scene, the exposure for the object would also depend on whether the object was in sunlight or shade. Depending on the scene and the objective, any of the previous exposures might be acceptable. However, in situations, the photographer might wish to specifically control the rendering of the dark object, with overall average metering. When it is important to control the rendering of specific scene elements, even when metering individual scene elements, some adjustment of the indicated exposure is often needed if the metered scene element is to be rendered as visualized. Much has been written on the Zone System, but the concept is very simple—render light subjects as light, and dark subjects as dark, according to the photographer’s visualization. The Zone System assigns numbers from 0 through 10 to different brightness values, with 0 representing black,5 middle gray, and 10 pure white, to make zones easily distinguishable from other quantities, Adams and Archer used Roman rather than Arabic numerals. Strictly speaking, zones refer to exposure, with a Zone V exposure resulting in a rendering in the final image. Each zone differs from the preceding or following zone by a factor of two, so that a Zone I exposure is twice that of Zone 0, and so forth, a one-zone change is equal to one stop, corresponding to standard aperture and shutter controls on a camera
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Abstract photography
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There has been no commonly-used definition of the term abstract photography. The term is both inclusive of a range of visual representations and explicit in its categorization of a type of photography that is visibly ambiguous by its very nature. Many photographers, critics, art historians and others have written or spoken about abstract photography without attempting to formalize a specific meaning, the proposed exhibition did not happen, yet Coburn later created some distinctly abstract photographs. Photographer and Professor of Psychology John Suler, in his essay Photographic Psychology, Image and Psyche and it draws away from natural appearances and recognizable subjects in the actual world. Some people even say it departs from true meaning, existence and it is an arena to test photography. German photographer and photographic theorist Gottfried Jäger used the term concrete photography, playing off the term concrete art and he said, More recently conceptual artist Mel Bochner hand wrote a quote from the Encyclopedia Britannia that said Photography cannot record abstract ideas. On a note card, then photographed it and printed it using six different photographic processes, some of the earliest images of what may be called abstract photography appeared within the first decade after the invention of the craft. In 1842 John William Draper created images with a spectroscope, which dispersed light rays into a previously unrecorded visible pattern. Draper saw his images as science records rather than art, but their quality is appreciated today for their groundbreaking status. Another early photographer, Anna Atkins in England, produced a book of photograms made by placing dried algae directly on cyanotype paper. Intended as a study, the stark white on blue images have an ethereal abstract quality due to the negative imaging. The discovery of the X-ray in 1895 and radioactivity in 1896 caused a public fascination with things that were previously invisible or unseen. In response, photographers began to explore how they could capture what could not been seen by human vision. About this same time Swedish author and artist August Strindberg experimented with subjecting saline solutions on photographic plates to heat, the images he produced with these experiments were indefinite renderings of what could not otherwise be seen and were thoroughly abstract in their presentation. The photographs he produced were blurry and indefinite, yet Darget was convinced that what he called thought vibrations were indistinguishable from light rays. A decade later the Armory Show in New York created a scandal by showing completely abstract works by Kandinsky, Braque, Duchamp, Robert Delaunay, the publics interest in and sometimes repulsion to abstract art was duly noted by some of the more creative photographers of the period. By 1910, in New York Alfred Stieglitz began to show abstract painters like Marsden Hartley and Arthur Dove at his 291 art gallery, photographers like Stieglitz, Paul Strand and Edward Steichen all experimented with depictive subjects photographed in abstract compositions. The first publicly exhibited images that are now recognized as abstract photographs were a series called Symmetrical Patterns from Natural Forms, two years later Alvin Langdon Coburn began experimenting with a series he called Vortographs
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Aerial photography
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Aerial photography is the taking of photographs of the ground from an elevated/direct-down position. Usually the camera is not supported by a ground-based structure, mounted cameras may be triggered remotely or automatically, hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that chase, Aerial photography was first practiced by the French photographer and balloonist Gaspard-Félix Tournachon, known as Nadar, in 1858 over Paris, France. However, the photographs he produced no longer exist and therefore the earliest surviving aerial photograph is titled Boston, as the Eagle, taken by James Wallace Black and Samuel Archer King on October 13,1860, it depicts Boston from a height of 630m. Kite aerial photography was pioneered by British meteorologist E. D. Archibald in 1882 and he used an explosive charge on a timer to take photographs from the air. Frenchman Arthur Batut began using kites for photography in 1888, Samuel Franklin Cody developed his advanced Man-lifter War Kite and succeeded in interesting the British War Office with its capabilities. The first use of a motion picture camera mounted to an aircraft took place on April 24,1909 over Rome in the 3,28 silent film short. The use of aerial photography rapidly matured during the war, as aircraft were equipped with cameras to record enemy movements. At the start of the conflict, the usefulness of aerial photography was not fully appreciated, germany adopted the first aerial camera, a Görz, in 1913. The French began the war with several squadrons of Blériot observation aircraft equipped with cameras for reconnaissance, the French Army developed procedures for getting prints into the hands of field commanders in record time. Frederick Charles Victor Laws started aerial photography experiments in 1912 with No.1 Squadron of the Royal Flying Corps, in 1916 the Austro-Hungarian Monarchy made vertical camera axis aerial photos above Italy for map-making. The camera was inserted into the floor of the aircraft and could be triggered by the pilot at intervals. In January 1918, General Allenby used five Australian pilots from No.1 Squadron AFC to photograph a 624 square miles area in Palestine as an aid to correcting and improving maps of the Turkish front and this was a pioneering use of aerial photography as an aid for cartography. Beginning 5 January, they flew with an escort to ward off enemy fighters. The first commercial aerial photography company in the UK was Aerofilms Ltd, founded by World War I veterans Francis Wills, the company soon expanded into a business with major contracts in Africa and Asia as well as in the UK. Operations began from the Stag Lane Aerodrome at Edgware, using the aircraft of the London Flying School, subsequently, the Aircraft Manufacturing Company, hired an Airco DH.9 along with pilot entrepreneur Alan Cobham. From 1921, Aerofilms carried out vertical photography for survey and mapping purposes, during the 1930s, the company pioneered the science of photogrammetry, with the Ordnance Survey amongst the companys clients. One Fairchild aerial survey aircraft in 1935 carried unit that combined two synchronized cameras, and each camera having five six inch lenses with a ten-inch lenses, each photo covered two hundred and twenty five square miles
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Architectural photography
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Architectural photography is the photographing of buildings and similar structures that are both aesthetically pleasing and accurate representations of their subjects. Architectural photographers are usually skilled in the use of specialized techniques, the first permanent photograph, View from the Window at Le Gras by Nicéphore Niépce, was also the first architectural photograph as it was a view of buildings. Similarly, photographs taken by early photographer William Henry Fox Talbot were of architecture, throughout the history of photography, buildings have been highly valued photographic subjects, mirroring societys appreciation for architecture and its cultural significance. By the 1860s, architectural photography started to become a visual medium. Much as building designs changed and broke with traditional forms, architectural photography also evolved, by the early 1950s, architects were hiring more photographers for commissioned work, resulting in architectural photography being viewed as more of an art form. A tenet of architectural photography is the use of perspective control and this is achieved by positioning the focal plane of the camera at so that it is perpendicular to the ground, regardless of the elevation of the camera eye. This result can be achieved by the use of cameras, tilt/shift lenses. Traditionally, view cameras have used for architectural photography as they allow for the lens to be tilted or shifted relative to the film plane. This allows for control of perspective, as well as a variety of creative possibilities, in a similar fashion to landscape photography, a deep depth of field is usually employed so that both the foreground and background are in sharp focus. More recently, digital single lens reflex cameras have used in the field of architectural photography. These cameras also employ detachable, tilt-shift lenses of varying focal lengths, architectural photography typically shows either the exterior or the interior of buildings. The techniques used in each of these types of photography are similar, interior architectural photography can also be performed with ambient light transmitted through windows and skylights, as well as interior lighting fixtures. Frequently though, architectural photographers will use supplemental lighting to improve the illumination within a building, either electronic flash strobes or incandescent hot lights can be used. A feature of architectural photography is that the subjects rarely move. It is therefore possible to use post-processing editing to achieve a lighting scheme
