1.
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
2.
Camera
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Thumb|A2016 Nikon D810 A camera is an optical instrument for recording or capturing images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies, the camera is a remote sensing device as it senses subjects without physical contact. The word camera comes from camera obscura, which means dark chamber and is the Latin name of the device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura, the functioning of the camera is very similar to the functioning of the human eye. A camera may work with the light of the spectrum or with other portions of the electromagnetic spectrum. A still camera is a device which creates a single image of an object or scene. All cameras use the basic design, light enters an enclosed box through a converging lens/convex lens. A shutter mechanism controls the length of time that light can enter the camera, a display, often a liquid crystal display, permits the user to view scene to be recorded and settings such as ISO speed, exposure, and shutter speed. A movie camera or a video camera operates similarly to a camera, except it records a series of static images in rapid succession. When the images are combined and displayed in order, the illusion of motion is achieved, the forerunner to the photographic camera was the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham s wrote very influential essays about experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents, before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. The first person to use this chemistry to create images was Thomas Wedgwood, to create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images werent permanent, however, as Wedgwood didnt employ a fixing mechanism and he ultimately failed at his goal of using the process to create fixed images created by a camera obscura. The first permanent photograph of an image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816, the photograph Niépce succeeded in creating shows the view from his window
3.
Flash (photography)
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A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene, other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs, modern cameras often activate flash units automatically. Flash units are built directly into a camera. Some cameras allow separate flash units to be mounted via an accessory mount bracket. In professional studio equipment, flashes may be large, standalone units, or studio strobes, studies of magnesium by Bunsen and Roscoe in 1859 showed that burning this metal produced a light with similar qualities to daylight. The potential application to photography inspired Edward Sonstadt to investigate methods of manufacturing magnesium so that it would burn reliably for this use and he applied for patents in 1862 and by 1864 had started the Manchester Magnesium Company with Edward Mellor. It also had the benefit of being a simpler and cheaper process than making round wire, mather was also credited with the invention of a holder for the ribbon, which formed a lamp to burn it in. The packaging also implies that the ribbon was not necessarily broken off before being ignited. An alternative to ribbon was flash powder, a mixture of powder and potassium chlorate, introduced by its German inventors Adolf Miethe. A measured amount was put into a pan or trough and ignited by hand, producing a brilliant flash of light, along with the smoke. This could be an activity, especially if the flash powder was damp. An electrically triggered flash lamp was invented by Joshua Lionel Cowen in 1899 and his patent describes a device for igniting photographers’ flash powder by using dry cell batteries to heat a wire fuse. Variations and alternatives were touted from time to time and a few found a measure of success in the marketplace, especially for amateur use. The use of powder in an open lamp was replaced by flashbulbs, magnesium filaments were contained in bulbs filled with oxygen gas. Manufactured flashbulbs were first produced commercially in Germany in 1929, such a bulb could only be used once, and was too hot to handle immediately after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. A later innovation was the coating of flashbulbs with a film to maintain bulb integrity in the event of the glass shattering during the flash
4.
Aluminium
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Aluminium or aluminum is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal, Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is combined in over 270 different minerals. The chief ore of aluminium is bauxite, Aluminium is remarkable for the metals low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the industry and important in transportation and structures, such as building facades. The oxides and sulfates are the most useful compounds of aluminium, despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals. Because of these salts abundance, the potential for a role for them is of continuing interest. Aluminium is a soft, durable, lightweight, ductile. It is nonmagnetic and does not easily ignite, a fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation. The yield strength of aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has about one-third the density and stiffness of steel and it is easily machined, cast, drawn and extruded. Aluminium atoms are arranged in a cubic structure. Aluminium has an energy of approximately 200 mJ/m2. Aluminium is a thermal and electrical conductor, having 59% the conductivity of copper. Aluminium is capable of superconductivity, with a critical temperature of 1.2 kelvin. Aluminium is the most common material for the fabrication of superconducting qubits, the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts, particularly in the presence of dissimilar metals. In highly acidic solutions, aluminium reacts with water to form hydrogen, primarily because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium
5.
Carbon fiber reinforced polymer
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Carbon fiber reinforced polymer, carbon fiber reinforced plastic or carbon fiber reinforced thermoplastic, is an extremely strong and light fiber-reinforced plastic which contains carbon fibers. The spelling fibre is common in British Commonwealth countries, the binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester or nylon, are sometimes used. The composite may contain other fibers, such as an aramid, aluminium, ultra-high-molecular-weight polyethylene or glass fibers, the properties of the final CFRP product can also be affected by the type of additives introduced to the binding matrix. The most frequent additive is silica, but other such as rubber. The material is referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer. In product advertisements, it is referred to simply as graphite fiber for short. In this case the composite consists of two parts, a matrix and a reinforcement, in CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a resin, such as epoxy. Because CFRP consists of two elements, the material properties depend on these two elements. The reinforcement will give the CFRP its strength and rigidity, measured by stress, unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber, the following equation, E c = V m E m + V f E f is valid for composite materials with the fibers oriented in the direction of the applied load. Typical epoxy-based CFRPs exhibit virtually no plasticity, with less than 0. 5% strain to failure, although CFRPs with epoxy have high strength and elastic modulus, the brittle fracture mechanics present unique challenges to engineers in failure detection since failure occurs catastrophically. As such, recent efforts to toughen CFRPs include modifying the existing epoxy material, One such material with high promise is PEEK, which exhibits an order of magnitude greater toughness with similar elastic modulus and tensile strength. However, PEEK is much more difficult to process and more expensive, despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue endurance limit. This means, theoretically, that stress cycle failure cannot be ruled out, environmental effects such as temperature and humidity can have profound effects on the polymer-based composites, including most CFRPs. While the carbon fibers themselves are not affected by the moisture diffusing into the material, the carbon fibers can cause galvanic corrosion when CRP parts are attached to aluminum. The primary element of CFRP is a filament, this is produced from a precursor polymer such as polyacrylonitrile, rayon. Precursor compositions and mechanical processes used during spinning filament yarns may vary among manufacturers, after drawing or spinning, the polymer filament yarns are then heated to drive off non-carbon atoms, producing the final carbon fiber
6.
Image stabilization
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Image stabilization is a family of techniques used to reduce blurring associated with the motion of a camera or other imaging device during exposure. Generally, it compensates for pan and tilt of the imaging device and it is used in image-stabilized binoculars, still and video cameras, astronomical telescopes, and also smartphones, mainly the high-end. With still cameras, camera shake is particularly problematic at slow speeds or with long focal length lenses. With video cameras, camera shake causes visible frame-to-frame jitter in the recorded video, in astronomy, the problem of lens-shake is added to by variations in the atmosphere over time, which will cause the apparent positions of objects to change. In photography, image stabilization can often permit the use of shutter speeds 2–4.5 stops slower, for example, at a focal length of 125 mm on a 35 mm camera, vibration or camera shake could affect sharpness if the shutter speed was slower than 1/125 second. The sharpness obtainable at a speed can increase dramatically. When calculating the effective length, it is important to take into account the image format a camera uses. For example, many digital SLR cameras use a sensor that is 2/3, 5/8. This means that the 35 mm frame is 1.5,1.6, the latter values are referred to as the crop factor, field-of-view crop factor, focal-length multiplier, or format factor. On a 2x crop factor camera, for instance, a 50 mm lens produces the field of view as a 100 mm lens used on a 35 mm film camera. However, image stabilization does not prevent motion blur caused by the movement of the subject or by extreme movements of the camera, Image stabilization is only designed for and capable of reducing blur that results from normal, minute shaking of a lens due to hand-held shooting. Some lenses and camera bodies include a secondary panning mode or a more aggressive active mode, image-stabilization features can also be a benefit in astrophotography, when the camera is technically—but not effectively—fixed in place. The Pentax K-5 and K-r can use their sensor-shift capability to reduce star trails in reasonable exposure times, in effect, the stabilization compensates for the Earths motion, not the cameras. There are two types of implementation - lens-based, or body-based stabilization and these refer to where the stabilizing system is located. Both have their advantages and disadvantages, an optical image stabilizer, often abbreviated OIS, IS, or OS, is a mechanism used in a still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor. This technology is implemented in the lens itself, as distinct from In Body Image Stabilization, the key element of all optical stabilization systems is that they stabilize the image projected on the sensor before the sensor converts the image into digital information. In Nikon and Canons implementation, it works by using a lens element that is moved orthogonally to the optical axis of the lens using electromagnets. Vibration is detected using two piezoelectric angular velocity sensors, one to detect movement and the other to detect vertical movement
7.
Sharpness (visual)
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In photography, the term acutance describes a subjective perception of sharpness that is related to the edge contrast of an image. Acutance is related to the amplitude of the derivative of brightness with respect to space, due to the nature of the human visual system, an image with higher acutance appears sharper even though an increase in acutance does not increase real resolution. Historically, acutance was enhanced chemically during development of a negative, in the example image, two light gray lines were drawn on a gray background. As the transition is instantaneous, the line is as sharp as can be represented at this resolution, acutance in the left line was artificially increased by adding a one-pixel-wide darker border on the outside of the line and a one-pixel-wide brighter border on the inside of the line. The actual sharpness of the image is unchanged, but the apparent sharpness is increased because of the greater acutance. In this somewhat overdone example most viewers will also be able to see the borders separately from the line, several image processing techniques, such as unsharp masking, can increase the acutance in real images. Low-pass filtering and resampling often cause overshoot, which increases acutance, but can also reduce absolute gradient, filtering and resampling can also cause clipping and ringing artifacts. An example is bicubic interpolation, widely used in processing for resizing images. Thus the acutance of an image is a vector field, coarse grain or noise can, like sharpening filters, increase acutance, hence increasing the perception of sharpness, even though they degrade the signal-to-noise ratio
8.
C-stand
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In film production, a C-stand is primarily used to position light modifiers, such as silks, nets, or flags, in front of light sources. The stand is constructed of metal and consists of a collapsible base, in addition, a C-stand includes a gobo head and a gobo arm, which provide the ability to articulate a light modifier without moving the stand itself. The legs of C stands are designed to be nested, so many stands can be placed around a light source, the term C-stand comes from the early history of lighting equipment where a popular sized sun reflector was 100 inches square or century. Today the term C-stand is a name for the grip stand made by Matthews studio equipment and has been copied by other manufacturers. A secondary use of C-stands is to position smaller light fixtures, a typical use would be to offset a backlight from the stand column, so that the stand itself can be placed out of shot, while the backlight hovers somewhere above the top edge of frame. In recent years, C-stands have found a new use, supporting the brackets used for balancing Steadicam camera sleds, due to the off-center weight distribution in this practice, it is necessary to use sandbags to add weight to the C-stand leg opposite the camera sled. A C-stand is sometimes referred to as a grip stand, while the grip department always carries C stands, sometimes the electric department may as well, for use well as lights that dont mount onto baby or junior stands, such as kinos. A baby C-stand is only 20 inches at its shortest height and it is nicknamed a Gary Coleman or a Billy Barty stand in the US. In the UK a short flag stand with legs is called a shotgun flag stand. A C-stand with a base is called a C-stand with a turtle base. The opening at the top of the turtle base accepts the base of c-stand upright or a junior pin, turtle bases are great for setting up a light very low to the ground. A C-stand with an upper most leg which is moveable on the axis is called a Stair Leg C-stand as the unit can be placed on a stairway. Also called a Rocky Mountain leg
9.
Fraxinus excelsior
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Fraxinus excelsior — known as the ash, or European ash or common ash to distinguish it from other types of ash — is a flowering plant species in the olive family Oleaceae. It is native throughout mainland Europe east to the Caucasus and Alborz mountains, the northernmost location is in the Trondheimsfjord region of Norway. The species is cultivated and reportedly naturalised in New Zealand and in scattered locales in the United States. It is a deciduous tree growing to 12–18 m tall with a trunk up to 2 m diameter, with a tall. The bark is smooth and pale grey on young trees, becoming thick, the shoots are stout, greenish-grey, with jet black buds. These features distinguish ash from ash in which the leaves are alternate with paired stipules. The leaves are often among the last to open in spring, the flowers are borne in short panicles, open before the leaves, and have no perianth. The female flowers are longer than the male flowers, dark purple, without petals. Both male and female flowers can occur on the same tree, a tree that is all male one year can produce female flowers the next, and similarly a female tree can become male. The fruit is a samara 2. 5–4.5 cm long and 5–8 mm broad, often hanging in bunches through the winter, European Ash rarely exceeds 250 years of age. However, there are numerous specimens estimated between 200 and 250 years old and there are a few over 250, the largest is in Clapton Court, England and is 9 m in girth. There are several examples over 4.5 metres in Derbyshire alone, Fraxinus excelsior is native to Europe from northern Spain to Russia, and from southern Scandinavia to northern Greece. It is also considered native in southwestern Asia from northern Turkey east to the Caucasus, the northernmost location is in the Trondheimsfjord region of Norway. It is native throughout the British Isles, particularly on limestone, as in northern Scotland, Ash occurs on a wide range of soil types, but is particularly associated with basic soils on calcareous substrates. As a young seedling it is tolerant, but as an older tree is light demanding. It is an early succession species and may well out compete beech and oak, unlike other Fraxinus species, F. excelsior does not form ectomycorrhizas. A number of Lepidoptera use the species as a food source, see Lepidoptera which feed on ashes. In the UK, many invertebrates have also been found to feed on Ash
10.
Screw thread
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A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread, a screw thread is the essential feature of the screw as a simple machine and also as a fastener. The mechanical advantage of a screw depends on its lead. This characteristic is essential to the vast majority of its uses, the tightening of a fasteners screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight elastic deformation. Screw threads have several applications, Fastening, Fasteners such as screws, machine screws, nuts. Connecting threaded pipes and hoses to each other and to caps, gear reduction via worm drives Moving objects linearly by converting rotary motion to linear motion, as in the leadscrew of a jack. Measuring by correlating linear motion to rotary motion, as in a micrometer, both moving objects linearly and simultaneously measuring the movement, combining the two aforementioned functions, as in a leadscrew of a lathe. In all of these applications, the thread has two main functions, It converts rotary motion into linear motion. It prevents linear motion without the corresponding rotation, every matched pair of threads, external and internal, can be described as male and female. For example, a screw has male threads, while its matching hole has female threads, the helix of a thread can twist in two possible directions, which is known as handedness. This is known as a thread, because it follows the right hand grip rule. Threads oriented in the direction are known as left-handed. By common convention, right-handedness is the default handedness for screw threads, therefore, most threaded parts and fasteners have right-handed threads. Left-handed thread applications include, Where the rotation of a shaft would cause a conventional right-handed nut to loosen rather than to tighten due to fretting induced precession, examples include, The left hand pedal on a bicycle. The left-hand grinding wheel on a bench grinder, the lug nuts on the left side of some automobiles. The securing nut on some circular saw blades - the large torque at startup should tend to tighten the nut. The spindle on brushcutter and line trimmer heads, so that the torque tends to tighten rather than loosen the connection In combination with right-hand threads in turnbuckles, in such a case, the coupling will have one right-handed and one left-handed thread. In some instances, for example early ballpoint pens, to provide a method of disassembly
11.
Unified Thread Standard
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The Unified Thread Standard defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, the UTS is currently controlled by ASME/ANSI in the United States. See the History of standardization section of the screw thread article, each thread in the series is characterized by its major diameter Dmaj and its pitch, P. UTS threads consist of a symmetric V-shaped thread. In the plane of the axis, the flanks of the V have an angle of 60° to each other. The outermost 0.125 and the innermost 0.25 of the height H of the V-shape are cut off from the profile, the pitch P is the distance between thread peaks. For UTS threads, which are threads, it is equal to the lead. UTS threads do not usually use the pitch parameter, instead a parameter known as threads per inch is used and this means that the external thread must end flat at Dmaj, but can be rounded out below the minor diameter Dmin. Conversely, in a thread, the major and minor diameters are minimum dimensions, therefore the thread profile must end flat at Dmin. For diameters smaller than 1⁄4 inch, the diameter is indicated by a number defined in the standard, for all other diameters. This number pair is followed by the letters UNC, UNF or UNEF if the diameter-pitch combination is from the coarse, fine or extra fine series. After several decades 1-14 fasteners have now come to be referred to as “Standard Fine Thread” or “UNF”. In other words, the 1-12 standard has lacked effective enforcement for a long time to give Generic trademark-like status to 1 inch 14 tpi fasteners. The following formula is used to calculate the diameter of a numbered screw greater than or equal to 0. For example, a number 10 calculates as, #10 ×0.013 in +0.060 in =0.190 in major diameter. To calculate the diameter of “ought” size screws count the number of extra 0’s and multiply this number by.013. For example the major diameter of a 0000 screw thread is.060 – =. 060-.039 =.021 inches and this defines a series of metric screws named after their major diameters in mm, from 0.30 UNM to 1.40 UNM. Preferred sizes are 0.3,0.4,0.5,0.6,0.8,1.0 and 1.2 mm, the standard thread pitch is approximately 1/4 of the major diameter
12.
British Standard Whitworth
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These three are collectively called Whitworth threads. The Whitworth thread was the worlds first national screw thread standard, until then, the only standardization was what little had been done by individual people and companies, with some companies in-house standards spreading a bit within their industries. Whitworths new standard specified a 55° thread angle and a depth of 0. 640327p and a radius of 0. 137329p. The thread pitch increases with diameter in steps specified on a chart, the Whitworth thread system was later to be adopted as a British Standard to become British Standard Whitworth. An example of the use of the Whitworth thread are the Royal Navys Crimean War gunboats, there were just ninety days in which to meet this requisition, and, short as the time was, the building of the gunboats presented no difficulty. It was otherwise however with the engines, and the Admiralty were in despair, suddenly, by a flash of the mechanical genius which was inherent in him, the late Mr John Penn solved the difficulty, and solved it quite easily. He had a pair of engines on hand of the exact size and he took them to pieces and he distributed the parts among the best machine shops in the country, telling each to make ninety sets exactly in all respects to the sample. An original example of the gunboat type engine was raised from the wreck of the SS Xantho by the Western Australian Museum, on disassembly, all its threads were shown to be of the Whitworth type. In the USA, BSW was replaced when steel replaced iron. American Unified Coarse was originally based on almost the same Imperial fractions, the Unified thread angle is 60° and has flattened crests. From 1/4 in up to 1 1/2 in, thread pitch is the same in both systems except that the pitch for the 1/2 in bolt is 12 threads per inch in BSW versus 13 tpi in the UNC. The form of a Whitworth thread is based on a triangle with an angle of 55° at each peak. The sides are at a angle of Θ =27. 5° to the perpendicular to the axis. Thus, if the pitch is p, the height of the fundamental triangle is H = p/ =0. 96049106 p. However, the top and bottom 1⁄6 of each of these triangles is cut off, so the depth of thread is 2⁄3 of that value. The peaks are further reduced by rounding them with a 2× = 180°−55° = 125° circular arc and this arc has a height of e = H sin Θ/6 =0. 073917569 p and a radius of r = e/ =0. 13732908 p. The British Standard Fine standard has the same angle as the BSW. This is more like the modern mechanical screw and was used for fine machinery, the British Standard Cycle standard which replaced the Cycle Engineers Institute standard was used on British bicycles and motorcycles
13.
Camcorder
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A camcorder is an electronic device combining a video camera and recorder. Although marketing materials may use the term camcorder, the name on the package. The earliest camcorders are tape-based, recording analog signals onto videotape cassettes, in 2006, digital recording became the norm, with tape replaced by storage media such as internal flash memory and SD cards. Earlier, the term camcorder exclusively referred to a camera with a recorder, but almost all of the electronic cameras built in 2006 provide recording capability essentially making them a camcorder. The term camcorder is now used for a particular camera range which provides advanced functions over more common cameras. Video cameras originally designed for television broadcast were large and heavy, mounted on special pedestals, as technology improved, out-of-studio video recording was possible with compact video cameras and portable video recorders, a detachable recording unit could be carried to a shooting location. Although the camera itself was compact, the need for a separate recorder made on-location shooting a two-person job, specialized videocassette recorders were introduced by JVC and Sony releasing a model for mobile work. Portable recorders meant that video footage could be aired on the early-evening news. In 1982, Sony released the Betacam system, a key component was a single camera-recorder unit, eliminating a cable between the camera and recorder and increasing the camera operators freedom. The Betacam used the same format as the Betamax, and became standard equipment for broadcast news. Sony released the first consumer camcorder in 1983, the Betamovie BMC-100P used a Betamax cassette and rested on the operators shoulder, due to a design not permitting a single-handed grip. That year, JVC released the first VHS-C camcorder, Sony introduced its compact Video8 format in 1985. That year, Panasonic, RCA and Hitachi began producing camcorders using a full-size VHS cassette with a three-hour capacity and these shoulder-mount camcorders were used by videophiles, industrial videographers and college TV studios. Full-size Super-VHS camcorders were released in 1987, providing a way to collect news segments or other videographies. Sony upgraded Video8, releasing the Hi8 in competition with S-VHS, Digital technology emerged with the Sony D1, a device which recorded uncompressed data and required a large amount of bandwidth for its time. In 1992 Ampex introduced DCT, the first digital video format with data compression using the cosine transform algorithm present in most commercial digital video formats. In 1995 Sony, JVC, Panasonic and other video-camera manufacturers launched DV, Panasonic launched DVCPRO HD in 2000, expanding the DV codec to support high definition. The format was intended for professional camcorders, and used full-size DVCPRO cassettes, in 2003 Sony, JVC, Canon and Sharp introduced HDV as the first affordable HD video format, due to its use of inexpensive MiniDV cassettes
14.
Page orientation
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Page orientation is the way in which a rectangular page is oriented for normal viewing. The two most common types of orientation are portrait and landscape, landscape originally described artistic outdoor scenes where a wide view area is needed, but the upper part of the painting would be mostly sky and so is omitted. Page orientation is used to describe the dimensions of a video display. The most common video display orientation is landscape mode, especially the 4,3 ratio, which is 4 units wide and 3 units tall, and the more recent 16,9 widescreen landscape display mode. Portrait screen orientation is used for computer displays, though less commonly than landscape. It is also common in public information displays, Portrait mode was first used on the Xerox Alto computer, which was considered technologically well ahead of its time when the system was first developed. The IBM DisplayWriter had a monitor and keyboard with large backspace key. Lanier, Wang, and CPT also made competing dedicated word processing computers with portrait modes, the height of the market for these computes was the late 1970s and early 1980s, prior to the introduction of the IBM PC. Thus, it had a keyboard without a large backspace key at first, within a short period of time, the DisplayWriter and other dedicated word processors were no longer available. However, Portrait Display Labs leaped into this niche, producing a number of rotating CRT monitors as well as software which could be used as a driver for many video cards. The later advent of the World Wide Web, whose pages are largely in portrait mode, when the Macintosh computer was introduced, WYSIWYG page layout using Aldus PageMaker became popular. The Macintosh rekindled interest in portrait displays, and the first portrait displays for it were developed by Radius Corporation, for the first computing devices a screen was built to operate in only portrait or landscape mode, and changing between orientations was not possible. Typically a custom controller board was needed to support the unusual screen orientation. As video display technology advanced, eventually the video board was able to accommodate rotation of the display. Rotation is now a feature of modern video cards, and is widely used in tablet PCs. Portrait mode is popular with arcade games that involve a vertically oriented playing area, such as Pac-Man, the vertical orientation allows greater detail along the vertical axis while conserving detail on the sides. This is why most early home versions of games have a wide. Portrait orientation is used occasionally within some arcade and home titles, primarily in the vertical shoot em up genre due to considerations of aesthetics, tradition
15.
Landscape
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A landscape is the visible features of an area of land, its landforms and how they integrate with natural or man-made features. The character of a landscape helps define the self-image of the people who inhabit it and it is the dynamic backdrop to people’s lives. Landscape can be as varied as farmland, a landscape park, the activity of modifying the visible features of an area of land is referred to as landscaping. There are several definitions of what constitutes a landscape, depending on context, the term landscape emerged around the turn of the sixteenth century to denote a painting whose primary subject matter was natural scenery. Land may be taken in its sense of something to people belong. The suffix ‑scape is equivalent to the more common English suffix ‑ship, the roots of ‑ship are etymologically akin to Old English sceppan or scyppan, meaning to shape. The suffix ‑schaft is related to the verb schaffen, so that ‑ship, the word landscape, first recorded in 1598, was borrowed from a Dutch painters term. An example of this usage can be found as early as 1662 in the Book of Common Prayer, Could we but climb where Moses stood. Setting, In works of narrative, it includes the moment in time and geographic location in which a story takes place. Picturesque, The word literally means in the manner of a picture, fit to be made into a picture, and used as early as 1703, gilpin’s Essay on Prints defined picturesque as a term expressive of that peculiar kind of beauty, which is agreeable in a picture. A view, A sight or prospect of some landscape or extended scene, wilderness, An uncultivated, uninhabited, and inhospitable region. Cityscape, The urban equivalent of a landscape, in the visual arts a cityscape is an artistic representation, such as a painting, drawing, print or photograph, of the physical aspects of a city or urban area. Seascape, A photograph, painting, or other work of art depicts the sea. Geomorphology is the study of the origin and evolution of topographic and bathymetric features created by physical or chemical processes operating at or near Earths surface. Geomorphology is practiced within physical geography, geology, geodesy, engineering geology, archaeology and this broad base of interests contributes to many research styles and interests within the field. The surface of Earth is modified by a combination of processes that sculpt landscapes, and geologic processes that cause tectonic uplift and subsidence. Many of these factors are strongly mediated by climate, the Earth surface and its topography therefore are an intersection of climatic, hydrologic, and biologic action with geologic processes. Desert, Plain, Taiga, Tundra, Wetland, Mountain, Mountain range, Cliff, Coast, Littoral zone, Glacier, Polar regions of Earth, Shrubland, Forest, Rainforest, Woodland, Jungle, Moors
16.
C-clamp
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This article refers to the clamp used to hold together two workpieces. For clamps used to stage lighting instruments to battens, see C-Clamp. At the top of the C is usually a flat edge. At the bottom is a hole through which a large threaded screw protrudes. When the clamp is completely closed, the end of the screw is in contact with the flat end on the frame. When the clamp is used, it is very rare that this occurs. Generally some other object or objects will be contained between the top and bottom flat edges, a G-clamp is used by means of turning the screw through the bottom of the frame until the desired state of pressure or release is reached. In the case that the clamp is being tightened, this is when the objects being secured are satisfactorily secured between the end of the screw and the flat end of the frame. If the clamp is being loosened, this is when a sufficient amount of force is released to allow the secured objects to be moved, while a G-clamp is a useful tool for woodworking, special care should be taken when working with any woods. The flat gripping edges of the frame, generally no larger than half an inch or a centimetre can cause indentations and this can be avoided by buffering between the clamp and the timber using two pieces of scrap wood. Deep-throated clamps are also available and provide greater reach for smaller jobs, see C-Clamp C-clamps are frequently used to hang stage lighting instruments
17.
Tripod head
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A tripod head is the part of a tripod system that attaches the supported device to the tripod legs, and allows the orientation of the device to be manipulated or locked down. Modular or stand-alone tripod heads can be used on a range of tripods. Integrated heads are built directly onto the legs, reducing the cost of the tripod system. The main function of any tripod head is to provide the ability to hold the attached device fixed in a specific orientation until the needs to change its position. In cinematography or video applications, a tripod head allows the operator to pan. The various types of heads available provide different control mechanisms and have distinct applications. Some can restrict movement to an axis, while others offer robotic movement to increase the precision of the movements. The materials used to construct tripod heads and the designs of various heads can be drastically different. In some situations a tripod head may be used without a set of tripod legs, heads can be attached to monopods to provide more versatility, or to a simple plate with a base mount for when the height of a full tripod is unnecessary. The base mount is the connection between the head and the tripod legs. Often the head will have a large, flat base that sits on top of the tripod. The actual connection between the two is made with a screw. A common standard for base mounts on photographic tripod equipment is a 3/8-16 screw on the tripod, tripods intended for smaller photographic equipment that do not need to be as rugged use a smaller 1/4-20 screw. The point where the head and the device attach is called the head mount. Most camera equipment includes a built-in female 1/4-20 receptacle, so the majority of tripod heads utilize a male 1/4-20 screw as their head mounts. Many consumer level tripod heads use the head mount to attach the camera. Camera mounting systems are used to make attaching and detaching devices to the quicker and easier. Many mounting systems are called quick-release systems, and utilize a two-piece mechanism, one piece is a plate that is affixed to the underside of the device, and the other piece is a receiver that is specifically designed to hold the plate
18.
Ball joint
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In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles. They are used on virtually every automobile made and work similarly to the design of the human hip joint. A ball joint consists of a stud and socket enclosed in a casing. The bearing stud is tapered and threaded, and fits into a hole in the steering knuckle. A protective encasing prevents dirt from getting into the joint assembly, usually, this is a rubber-like boot that allows movement and expansion of lubricant. Motion-control ball joints tend to be retained with an internal spring, the offset ball joint provides means of movement in systems where thermal expansion and contraction, shock, seismic motion, and torsional motions, and forces are present. A ball joint is used for allowing free movement in two planes at the time, including rotating in those planes. Combining two such joints with control arms enables motion in all three planes, allowing the front end of an automobile to be steered and a spring and shock suspension to make the ride comfortable. Camber angle could generally be adjusted by moving both inner pivots of either the upper or lower control arm inwards or outwards by an equal amount. But compliance of the control arm inner pivots, typically due to the use of elastomeric bearings and this ability to fine-tune ball-jointed suspension allows manufacturers to make the automobile more stable and easier to steer, compared to the older kingpin style suspension. The smoother ride may also increase tire tread life, since the ball-joint suspension allows better control of suspension geometry, on modern vehicles, ball joints are the pivot between the wheels and the suspension of an automobile. Ball joints play a role in the safe operation of an automobiles steering. So, there are only two ball joints in the suspension, however there will be at least four in the steering linkage. In non-MacPherson strut automobile suspension, the two joints are called the upper ball joint and lower ball joint. Lower ball joints are sometimes larger and may wear out faster, because the fore and aft loads, also, lateral cornering loads are higher at the bottom joint. Depending on the design, the vertical load from the suspension spring may be handled entirely by the top ball joint. The damper load, is usually, but not always, taken on the ball joint as the spring load. The anti-roll bar loading is often, but not always, taken on the ball joint
19.
Rotation
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A rotation is a circular movement of an object around a center of rotation. A three-dimensional object always rotates around a line called a rotation axis. If the axis passes through the center of mass, the body is said to rotate upon itself. A rotation about a point, e. g. the Earth about the Sun, is called a revolution or orbital revolution. The axis is called a pole, mathematically, a rotation is a rigid body movement which, unlike a translation, keeps a point fixed. This definition applies to rotations within both two and three dimensions All rigid body movements are rotations, translations, or combinations of the two, a rotation is simply a progressive radial orientation to a common point. That common point lies within the axis of that motion, the axis is 90 degrees perpendicular to the plane of the motion. If the axis of the rotation lies external of the body in question then the body is said to orbit, there is no fundamental difference between a “rotation” and an “orbit” and or spin. The key distinction is simply where the axis of the rotation lies and this distinction can be demonstrated for both “rigid” and “non rigid” bodies. If a rotation around a point or axis is followed by a rotation around the same point/axis. The reverse of a rotation is also a rotation, thus, the rotations around a point/axis form a group. However, a rotation around a point or axis and a rotation around a different point/axis may result in something other than a rotation, Rotations around the x, y and z axes are called principal rotations. Rotation around any axis can be performed by taking a rotation around the x axis, followed by a rotation around the y axis and that is to say, any spatial rotation can be decomposed into a combination of principal rotations. In flight dynamics, the rotations are known as yaw, pitch. This terminology is used in computer graphics. In astronomy, rotation is an observed phenomenon. Stars, planets and similar bodies all spin around on their axes, the rotation rate of planets in the solar system was first measured by tracking visual features. Stellar rotation is measured through Doppler shift or by tracking active surface features and this rotation induces a centrifugal acceleration in the reference frame of the Earth which slightly counteracts the effect of gravity the closer one is to the equator
20.
Panning (camera)
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In cinematography and photography panning means swiveling a still or video camera horizontally from a fixed position. This motion is similar to the motion of a person when they turn their head on their neck from left to right. The term panning is short for panorama, suggesting a view that exceeds the gaze. Panning, in words, is a device for gradually revealing and incorporating off-screen space into the image. Panning should never be confused with tracking or travelling, in which the camera is not just swivelled but is physically displaced left or right, in video technology, panning refers to the horizontal scrolling of an image wider than the display. For 3D modeling in computer graphics, panning means moving parallel to the current view plane, in other words, the camera moves perpendicular to the direction it is pointed. The technique also has limited applications in still photography, in other disciplines, this motion is called yaw. When photographing a subject, the panning technique is achieved by keeping the subject in the same position of the frame for the duration of the exposure. The length of the exposure must be enough to allow the background to blur due to the movement of the camera as the photographer follows the subject in the viewfinder. The exact length of exposure required will depend on the speed at which the subject is moving, the length of the lens. The faster shutter speed allowed by fast moving subjects are easier to capture in a smoothly panned shot. With slower moving subjects, the risk is that the motion will be jerky. To aid in capturing panned pictures, photographers use aids such as tripods and monopods, a low budget option is to tie a piece of string around the lens, then to drop the other end to the floor and step on it to pull it taut. This will allow a bit more stability and allow for smoother blur
21.
Handle
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A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of type of handle involves substantial ergonomic issues. Handles for tools are an important part of their function, enabling the user to exploit the tools to maximum effect, the three nearly universal requirements of are, Sufficient strength to support the object, or to otherwise transmit the force involved in the task the handle serves. Sufficient length to permit the hand or hands gripping it to exert that force. Sufficiently small circumference to permit the hand or hands to surround it far enough to grip it as solidly as needed to exert that force. Other requirements may apply to specific handles, A sheath or coating on the handle that provides friction against the hand, designs such as recessed car-door handles, reducing the chance of accidental operation, or simply the inconvenience of snagging the handle. Sufficient circumference to distribute the force comfortably and safely over the hand, design to thwart unwanted access, for example, by children or thieves. In these cases many of the requirements may have reduced importance. For example, a child-proof doorknob can be difficult for even an adult to use, one major category of handles are pull handles, where one or more hands grip the handle or handles, and exert force to shorten the distance between the hands and their corresponding shoulders. The three criteria stated above are universal for pull handles, many pull handles are for lifting, mostly on objects to be carried. Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors, the inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage. Pull handles are also a frequent host of common door handle bacteria such as e-coli, some throwing motions, as in a track-and-field hammer throw, involve pulling on a handle against centrifugal force, in the course of accelerating the thrown object by forcing it into circular motion. Another category of hand-operated device requires grasping and rotating the hand and either the arm or the whole arm. When the grip required is a fist grip, as with a handle that has an arm rather than a knob to twist
22.
Gear
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A gear or cogwheel is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source, Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The teeth on the two meshing gears all have the same shape, two or more meshing gears, working in a sequence, are called a gear train or a transmission. A gear can mesh with a linear toothed part, called a rack, the gears in a transmission are analogous to the wheels in a crossed, belt pulley system. An advantage of gears is that the teeth of a gear prevent slippage, in transmissions with multiple gear ratios—such as bicycles, motorcycles, and cars—the term gear as in first gear refers to a gear ratio rather than an actual physical gear. The term describes similar devices, even when the ratio is continuous rather than discrete, or when the device does not actually contain gears. Early examples of gears date from the 4th century BC in China, examples of further development include, Ma Jun used gears as part of a south-pointing chariot. The Antikythera mechanism is an example of an early and intricate geared device. Its time of construction is now estimated between 150 and 100 BC, the water-powered grain-mill, the water-powered saw mill, fulling mill, and other applications of watermill often used gears. The first mechanical clocks were built in AD725, the 1386 Salisbury cathedral clock may be the worlds oldest working mechanical clock. The definite ratio that teeth give gears provides an advantage over other drives in precision machines such as watches that depend upon an exact velocity ratio, an external gear is one with the teeth formed on the outer surface of a cylinder or cone. Conversely, a gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, a gear is one with the pitch angle exceeding 90 degrees. Internal gears do not cause output shaft direction reversal, spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with teeth projecting radially, though the teeth are not straight-sided, the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears mesh together correctly only if fitted to parallel shafts, No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds, helical or dry fixed gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, since the gear is curved, this angling makes the tooth shape a segment of a helix
23.
Macro photography
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Macro photography, is extreme close-up photography, usually of very small subjects and living organisms like insects, in which the size of the subject in the photograph is greater than life size. By some definitions, a photograph is one in which the size of the subject on the negative or image sensor is life size or greater. However, in other uses it refers to a photograph of a subject at greater than life size. The ratio of the size on the film plane to the actual subject size is known as the reproduction ratio. Likewise, a lens is classically a lens capable of reproduction ratios of at least 1,1, although it often refers to any lens with a large reproduction ratio. For example, when producing a 6×4 inch print using 35 format film or sensor, reproduction ratios much greater than 1,1 are considered to be photomicrography, often achieved with digital microscope. In the digital age, a macro photograph can be more practically defined as a photograph with a vertical subject height of 24 mm or less. The term photo-macrograph was proposed in 1899 by W. H. Walmsley for close-up images with less than 10 diameters magnification, one of the earliest pioneers of macro photography was Percy Smith, born in 1880. He was a British nature documentary filmmaker, and was known for his close-up photographs, Macro lenses specifically designed for close-up work, with a long barrel for close focusing and optimized for high reproduction ratios, are one of the most common tools for macro photography. Most modern macro lenses can focus continuously to infinity as well, others, such as the Infinity Photo-Opticals TS-160 can achieve magnifications from 0-18x on sensor, focusing from infinity down to 18 mm from the object. The further the lens is from the film or sensor, the closer the distance, the greater the magnification. Tubes of various lengths can be stacked, decreasing lens-to-subject distance, bellows or tubes eliminate infinity focus. Placing an auxiliary close-up lens in front of the lens is another option. Inexpensive screw-in or slip-on attachments provide close focusing and this method works with cameras that have fixed lenses, and is commonly used with bridge cameras. These lenses add diopters to the power of the lens, decreasing the minimum focusing distance. They are typically designated by their diopter, and can be stacked to achieve the desired magnification, photographers may employ view camera movements and the Scheimpflug principle to place an object close to the lens in focus, while maintaining selective background focus. This technique requires the use of a camera or perspective control lens with the ability to tilt the lens with respect to the film or sensor plane. Traditional view cameras permit such adjustment as part of their design, ordinary lenses can be used for macro photography by using a reversing ring
24.
Altazimuth mount
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An altazimuth or alt-azimuth mount is a simple two-axis mount for supporting and rotating an instrument about two perpendicular axes – one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth of the direction of the instrument. Rotation about the horizontal axis varies the altitude of the pointing direction and these mounts are used, for example, with telescopes, cameras, radio antennas, heliostat mirrors, solar panels, and guns and similar weapons. Several names are given to this kind of mount, including altitude-azimuth, azimuth-elevation, a gun turret is essentially an alt-azimuth mount for a gun, and a standard camera tripod is an alt-azimuth mount as well. When used as a telescope mount, the biggest advantage of an alt-azimuth mount is the simplicity of its mechanical design. The primary disadvantage is its inability to follow objects in the night sky as the Earth spins on its axis. On the other hand, an equatorial mount only needs to be rotated about an axis, at a constant rate. Altazimuth mounts need to be rotated about both axes at variable rates, achieved via microprocessor based two-axis drive systems, to track equatorial motion and this imparts an uneven rotation to the field of view that also has to be corrected via a microprocessor based counter rotation system. The design also does not allow for the use of setting circles to locate astronomical objects although modern digital setting circles have removed this shortcoming. Another limitation is the problem of gimbal lock at zenith pointing, when tracking at elevations close to 90°, the azimuth axis must rotate very quickly, if the altitude is exactly 90°, the speed is infinite. Thus, altazimuth telescopes, although they can point in any direction, cannot track smoothly within a zenith blind spot, typical current applications of altazimuth mounts include, Research telescopes Mounts for very large telescopes. In the largest telescopes the mass and cost of a mount is prohibitive. The simple structure of an alt-azimuth mount allows significant cost reductions, an altazimuth mount also reduces the cost in the dome structure covering the telescope since the simplified motion of the telescope means the structure can be more compact. Altazimuth mounts are cheap and simple to use
25.
Equatorial mount
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An equatorial mount is a mount for instruments that compensate the rotation of earth by having one rotational axis parallel to the Earths axis of rotation. This type of mount is used for astronomical telescopes and cameras, such an arrangement is called a sidereal drive. In astronomical telescope mounts, the axis is paired with a second perpendicular axis of motion. They may also be equipped with setting circles to allow for the location of objects by their celestial coordinates, equatorial mounts differ from mechanically simpler altazimuth mounts, which require variable speed motion around both axes to track a fixed object in the sky. Equatorial telescope mounts come in many designs, in the last twenty years motorized tracking has increasingly been supplemented with computerized object location. Digital setting circles take a computer with an object database that is attached to encoders. The computer monitors the telescopes position in the sky, the operator must push the telescope. Go-to systems use servo motors and the operator need not touch the instrument at all to change its position in the sky. The computers in these systems are typically either hand-held in a paddle or supplied through an adjacent laptop computer which is also used to capture images from an electronic camera. The electronics of modern telescope systems often include a port for autoguiding, a special instrument tracks a star and makes adjustment in the telescopes position while photographing the sky. To do so the autoguider must be able to issue commands through the control system. These commands can compensate for very slight errors in the tracking performance, in new observatory designs, equatorial mounts have been out of favor for decades in large-scale professional applications. Massive new instruments are most stable when mounted in an alt-azimuth configuration, computerized tracking and field-derotation are not difficult to implement at the professional level. At the amateur level, however, equatorial mounts remain popular, in the German equatorial mount, the primary structure is a T-shape, where the lower bar is the right ascension axis, and the upper bar is the declination axis. The telescope is placed on one end of the axis. The right ascension axis has bearings below the T-joint, that is, the Open Fork mount has a Fork attached to a right ascension axis at its base. The telescope is attached to two points at the other end of the fork so it can swing in declination. Most modern mass-produced catadioptric reflecting telescopes tend to be of this type, the mount resembles an Altazimuth mount, but with the azimuth axis tilted and lined up to match earth rotation axis with a piece of hardware usually called a wedge
26.
Stick-slip phenomenon
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The stick-slip phenomenon, also known as the slip-stick phenomenon or simply stick-slip, is the spontaneous jerking motion that can occur while two objects are sliding over each other. Below is a simple, heuristic description of stick-slip phenomena using classical mechanics that is relevant for engineering descriptions, however, in actuality, there is little consensus in academia regarding the actual physical description of stick-slip which follows the lack of understanding about friction phenomena in general. The stiffness of the spring, the load at the interface, the duration of time the interface has existed. A description using common phonons provides explanations for noise that generally accompanies stick-slip through surface acoustic waves, the use of complicated constitutive models that lead to discontinuous solutions end up requiring unnecessary mathematical effort and do not represent the true physical description of the system. However, such models are useful for low fidelity simulations. Engineering description Stick-slip can be described as alternating between sticking to each other and sliding over each other, with a corresponding change in the force of friction. Typically, the friction coefficient between two surfaces is larger than the kinetic friction coefficient. If an applied force is enough to overcome the static friction. The attached picture shows symbolically an example of stick-slip, V is a drive system, R is the elasticity in the system, and M is the load that is lying on the floor and is being pushed horizontally. The load starts sliding and the friction coefficient decreases from its value to its dynamic value. At this moment the spring can give power and accelerates M. During M’s movement, the force of the spring decreases, until it is insufficient to overcome the dynamic friction, from this point, M decelerates to a stop. The drive system however continues, and the spring is loaded again etc, examples of stick-slip can be heard from hydraulic cylinders, tractor wet brakes, honing machines etc. Special dopes can be added to the fluid or the cooling fluid to overcome or minimize the stick-slip effect. Stick-slip is also experienced in lathes, mill centres, and other machinery where something slides on a slideway, slideway oils typically list prevention of stick-slip as one of their features. Other examples of the phenomenon include the music that comes from bowed instruments, the noise of car brakes and tires. Stick-slip also has been observed in articular cartilage in mild loading and sliding conditions, another example of the stick-slip phenomenon occurs when musical notes are played with a glass harp by rubbing a wet finger along the rim of a crystal wine glass. One animal that produces sound using stick-slip friction is the spiny lobster which rubs its antennae over smooth surfaces on its head, another, more common example which produces sound using stick-slip friction is the grasshopper
27.
Gimbal
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A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of three gimbals, one mounted on the other with orthogonal axes, may be used to allow an object mounted on the innermost gimbal to remain independent of the rotation of its support. The gimbal suspension used for mounting compasses and the like is sometimes called a Cardan suspension after Italian mathematician, however, Cardano did not invent the gimbal, nor did he claim to. The device has been known since antiquity, first described in the 3rd c, BCE by Philo of Byzantium, although some modern authors support it may not have a single identifiable inventor. The gimbal was first described by the Greek inventor Philo of Byzantium and this was done by the suspension of the inkwell at the center, which was mounted on a series of concentric metal rings so that it remained stationary no matter which way the pot is turned. Thus, the sinologist Joseph Needham suspected Arab interpolation as late as 1965, however, Carra de Vaux, author of the French translation which still provides the basis for modern scholars, regards the Pneumatics as essentially genuine. The historian of technology George Sarton also asserts that it is safe to assume the Arabic version is a copying of Philos original. So does his colleague Michael Lewis, after antiquity, gimbals remained widely known in the Near East. In the Latin West, reference to the device appeared again in the 9th century recipe book called the Little Key of Painting Mappae clavicula, the French inventor Villard de Honnecourt depicts a set of gimbals in his famous sketchbook. In the early period, dry compasses were suspended in gimbals. In China, the Han Dynasty inventor Ding Huan created a gimbal incense burner around 180 CE, there is a hint in the writing of the earlier Sima Xiangru that the gimbal existed in China since the 2nd century BCE. There is mention during the Liang Dynasty that gimbals were used for hinges of doors and windows, extant specimens of Chinese gimbals used for incense burners date to the early Tang Dynasty, and were part of the silver-smithing tradition in China. In this application, the measurement unit is equipped with three orthogonally mounted gyros to sense rotation about all axes in three-dimensional space. The gyro outputs are kept to a null through drive motors on each gimbal axis, to accomplish this, the gyro error signals are passed through resolvers mounted on the three gimbals, roll, pitch and yaw. These resolvers perform an automatic matrix transformation according to each gimbal angle, the yaw torques must be resolved by roll and pitch transformations. The gimbal angle is never measured, similar sensing platforms are used on aircraft. In inertial navigation systems, gimbal lock may occur when vehicle rotation causes two of the three rings to align with their pivot axes in a single plane. When this occurs, it is no longer possible to maintain the sensing platforms orientation, to control roll, twin engines with differential pitch or yaw control signals are used to provide torque about the vehicles roll axis
28.
Monopod
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A monopod, also called a unipod, is a single staff or pole used to help support cameras, video cameras, binoculars, rifles or other precision instruments in the field. The monopod allows a camera to be held steadier, allowing the photographer to take sharp pictures at slower shutter speeds. In the case of video, it reduces camera shake, monopods are easier to transport and quicker to set up than conventional tripods, making them preferable for on-the-go photography. An OTG photographer is not able to carry a heavy, bulky tripod around, when used by itself, it eliminates camera shake in the vertical axis. When used in combination with leaning against an object, a bipod is formed. Unlike a tripod, monopods cannot support a camera independently, in the case of still cameras, this limits the shutter speed that can be used. They still allow lower shutter speeds than hand holding, and are easier to carry, many monopods can also be used as a beltpod, meaning that the foot of the monopod can rest on the belt or hip of the photographer. This is usually used in selfies for clearer shots by ensuring that the camera is not in motion relative to the body, with a special adapter, monopods can be used as a chestpod, meaning that the foot rests now on the chest of the photographer. The result is that the camera is held more steadily than by hand alone, and this technique is widely used in videography in which the photographer has to move with the subject e. g first-person scenes, and is also especially useful for disabled photographers. Walking sticks or trekking poles exist that have a 1/4-20 threaded stud on the top of the handle, usually covered by a cap when not in use, the user would usually need to carry a ball swivel adapter separately and mount it as needed. Monopods used with a smartphone or camera to take selfie photographs beyond the reach of the arm are known as selfie sticks. There are two ways to attach your camera to a monopod, the first is to screw the monopods screw thread directly into the camera body. This is fine if youre using a small, light lens. If youre shooting using a long, heavy telephoto lens, its better to use a tripod mount ring and this fixes the monopod to the lens rather than the camera body, giving better balance and stopping the monopod from rotating in your hands as you try to position it. There are various different types of monopod head available, and ball heads offer the most flexibility and they allow you to shoot in portrait or landscape orientation, and angle your camera to adjust for any sloping of the monopod. A monopod can be used for firearms and they have the advantage of being light and compact, although when used in firing mode they can only be used with small firearms. They are also used as butt spikes as a support on precision rifles. When used to support a compass or transit, the monopod is referred to as a jacob staff, mounting the compass atop the jacob staff eliminates reading errors introduced by body movements, and permits the taking of more precise bearings to targets
29.
Degrees of freedom (mechanics)
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In physics, the degree of freedom of a mechanical system is the number of independent parameters that define its configuration. The position of a car moving along a track has one degree of freedom because the position of the car is defined by the distance along the track. A train of rigid cars connected by hinges to an engine still has one degree of freedom because the positions of the cars behind the engine are constrained by the shape of the track. An automobile with highly stiff suspension can be considered to be a body traveling on a plane. This body has three independent degrees of freedom consisting of two components of translation and one angle of rotation, skidding or drifting is a good example of an automobiles three independent degrees of freedom. The position and orientation of a body in space is defined by three components of translation and three components of rotation, which means that it has six degrees of freedom. The exact constraint mechanical design method manages the degrees of freedom to neither underconstrain nor overconstrain a device, the number of rotational degrees of freedom comes from the dimension of the rotation group SO. A non-rigid or deformable body may be thought of as a collection of many minute particles, when motion involving large displacements is the main objective of study, a deformable body may be approximated as a rigid body in order to simplify the analysis. The degree of freedom of a system can be viewed as the number of coordinates required to specify a configuration. This reduces the degree of freedom of the system to five, see also Euler angles The trajectory of an airplane in flight has three degrees of freedom and its attitude along the trajectory has three degrees of freedom, for a total of six degrees of freedom. The mobility formula counts the number of parameters that define the configuration of a set of bodies that are constrained by joints connecting these bodies. Consider a system of n rigid bodies moving in space has 6n degrees of freedom measured relative to a fixed frame. In order to count the degrees of freedom of this system, include the frame in the count of bodies. Then the degree-of-freedom of the system of N = n +1 is M =6 n =6. Joints that connect bodies in this system remove degrees of freedom, specifically, hinges and sliders each impose five constraints and therefore remove five degrees of freedom. It is convenient to define the number of constraints c that a joint imposes in terms of the joints freedom f, where c =6 − f. In the case of a hinge or slider, which are one degree of freedom joints, have f =1, the result is that the mobility of a system formed from n moving links and j joints each with freedom fi, i =1. J, is given by M =6 n − ∑ i =1 j =6 + ∑ i =1 j f i Recall that N includes the fixed link, there are two important special cases, a simple open chain, and a simple closed chain
30.
Low-angle shot
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In cinematography, a low-angle shot, is a shot from a camera angle positioned low on the vertical axis, anywhere below the eye line, looking up. Sometimes, it is directly below the subjects feet. Psychologically, the effect of the shot is that it makes the subject look strong. M, Inspector Karl Lohmann is shot in low angle in his office, also, two disputing men, one small and the other tall, are shot in low and high angles, respectively. Citizen Kane, there are many such as during the scene where Kane fires Leland. In fact, the scene where Leland confronts Kane after his defeat in the election is entirely shot in a low angle view, psycho, the house where Norman Bates lives is usually shot from a low angle. Star Wars, Darth Vader is often shot at a low angle, for example, touch of Evil, In this film noir, Hank Quinlan is often shot in low angle to make him look menacing, large, and in-charge. The Lady From Shanghai, examples of low-angle shot are during the scene where George Grisby is confronted by Broome, used while filming World Wrestling Entertainment interviews with André the Giant. In this scene, the angle actually goes from a medium close up. Full Metal Jacket, examples of a low angle shot is during the scene where the boot camp Sgt. is yelling at Joker. The Untouchables, there is a shot during the scene where Frank Nitti is being searched outside the courtroom
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Cinematography
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Typically, a lens is used to repeatedly focus the light reflected from objects into real images on the light-sensitive surface inside a camera during a questioned exposure, creating multiple images. With an electronic sensor, this produces an electrical charge at each pixel. The result with photographic emulsion is a series of invisible latent images on the film stock, the images on the film stock are played back at a rapid speed and projected onto a screen, creating the illusion of motion. Cinematography finds uses in fields of science and business as well as for entertainment purposes. The word cinematography was created from the Greek words κίνημα, meaning movement, motion and γράφειν meaning to record, the word used to refer to the art, process, or job of filming movies, but later its meaning was restricted to motion picture photography. In the 1830s, moving images were produced on revolving drums and disks, with independent invention by Simon von Stampfer in Austria, Joseph Plateau in Belgium, and William Horner in Britain. In 1845, Francis Ronalds invented the first successful camera able to make recordings of the varying indications of meteorological. The cameras were supplied to numerous observatories around the world and some remained in use well into the 20th century. William Lincoln patented a device, in 1867, that showed animated pictures called the wheel of life or zoopraxiscope, in it, moving drawings or photographs were watched through a slit. On 19 June 1873, Eadweard Muybridge successfully photographed a horse named Sallie Gardner in fast motion using a series of 24 stereoscopic cameras. The cameras were arranged along a parallel to the horses. They were 21 inches apart to cover the 20 feet taken by the horse stride, although it was never played back at speed to create motion, this was the first step towards motion pictures. The late nineteenth to the twentieth century brought rise to the use of film not only for entertainment purposes. The experimental film Roundhay Garden Scene, filmed by Louis Le Prince on 14 October 1888, in Roundhay, Leeds and this movie was shot on paper film. W. K. L. Dickson, working under the direction of Thomas Alva Edison, was the first to design a successful apparatus and this camera took a series of instantaneous photographs on standard Eastman Kodak photographic emulsion coated onto a transparent celluloid strip 35 mm wide. The results of work were first shown in public in 1893, using the viewing apparatus also designed by Dickson. Contained within a box, only one person at a time looking into it through a peephole could view the movie. The Lumière brothers were the first to present projected, moving, photographic, in 1896, movie theaters were open in France, Italy, Brussels, and London
32.
Camera angle
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The camera angle marks the specific location at which the movie camera or video camera is placed to take a shot. A scene may be shot from camera angles simultaneously. This will give a different experience and sometimes emotion, the different camera angles will have different effects on the viewer and how they perceive the scene that is shot. There are a few different routes that an operator could take to achieve this effect. The typical shot measurements unit is the milliframe, milliframes are used to calculate how much the shot should be moved to perfect the camera angles. However, the size of a milliframe is almost impossible to calculate since it is not a physical measurement. Where the camera is placed in relation to the subject can affect the way the viewer perceives the subject, there are a number of camera angles, such as a high-angle shot, a low-angle shot, a birds-eye view and a worms-eye view. A Viewpoint is the apparent distance and angle from which the camera views and they also include the eye-level camera angle and the point of view shot. A high-angle shot is a shot in which the camera is physically higher than the subject and is looking down upon the subject. The high angle shot can make the subject look small or weak or vulnerable while a shot is taken from below the subject and has the power to make the subject look powerful or threatening. A neutral shot or eye-level shot has little to no effect on the viewer. This shot is when the camera is level or looking straight on with the subject, a point of view shot shows the viewer the image through the subjects eye. Some POV shots use hand-held cameras to create the illusion that the viewer is seeing through the subjects eyes, birds eye shot or birds-eye view shots are taken directly above the scene to establish the landscape and the actors relationship to it. When considering the camera one must remember that each shot is its own individual shot. There are many different types of shots that can be used from these angles, there are extreme long shots which are extremely far away from the subject and might not even show a person at all. Extreme long shots are usually done in an angle so the viewer can look down upon a setting or scene. Extreme longs shots are used mainly to open the scene or narrative, the rest of the shots are most typically done in an eye level or point of view shot although it is possible to do any shot with any angle. There is the shot which shows the subject even though the setting still dominates the picture frame
33.
Close-up
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A close-up or closeup in filmmaking, television production, still photography and the comic strip medium is a type of shot, which tightly frames a person or an object. Close-ups are one of the shots used regularly with medium shots. Close-ups display the most detail, but they do not include the broader scene, moving in to a close-up or away from a close-up is a common type of zooming. Most early filmmakers—such as Thomas Edison, Auguste and Louis Lumière and Georges Méliès—tended not to use close-ups and preferred to frame their subjects in long shots, film historians disagree as to which filmmaker first used a close-up. In 1901, James Williamson, also working in Hove, made perhaps the most extreme close-up of all in The Big Swallow, when his character approaches the camera and appears to swallow it. D. W. Griffith, who pioneered screen cinematographic techniques, for example, one of Griffiths short films, The Lonedale Operator, makes significant use of a close-up of a wrench that a character pretends is a gun. Lillian Gish remarked on Griffiths pioneering use of the close-up, The people in the front office got very upset and they came down and said, The public doesn’t pay for the head or the arms or the shoulders of the actor. Let’s give them their money’s worth. ’ Griffith stood very close to them and said, ‘Can you see my feet. ’ When they said no, he replied, I am using what the eyes can see. Close-ups are used in ways and for many reasons. They are often employed as cutaways from a distant shot to show detail, such as characters emotions. Close cuts to characters faces are used far more often in television than in movies, for a director to deliberately avoid close-ups may create in the audience an emotional distance from the subject matter. Close-ups are used for distinguishing main characters, major characters are often given a close-up when they are introduced as a way of indicating their importance. Leading characters will have multiple close-ups, there is a long-standing stereotype of insecure actors desiring a close-up at every opportunity and counting the number of close-ups they received. Close-up shots do not show the subject in the context of its surroundings. If overused, they may leave viewers uncertain as to what they are seeing, Close-ups are rarely done with wide-angle lenses, because perspective causes objects in the center of the picture to be unnaturally enlarged. Certain times, different directors will use wide-angle lenses, because they can convey the message of confusion, there are various degrees of close-up depending on how tight the shot is. The terminology varies between countries and even different companies, but in general these are, Medium Close Up, usually covers the subjects head and shoulders. Close Up, A certain feature, such as someones head, extreme Close Up, The shot is so tight that only a detail of the subject, such as someones eyes, can be seen
34.
Long shot
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In photography, filmmaking and video production, a long shot typically shows the entire object or human figure and is usually intended to place it in some relation to its surroundings. These are typically shot now using wide angle cameras However due to the sheer distance establishing shots and this type of filmmaking was a result of filmmakers trying to retain the sense of the viewer watching a play in front of them, as opposed to just a series of pictures. The wide shot has been used since films have made as it is a very basic type of cinematography. In the 1878, the one of the first true motion pictures, even though this wouldn’t be considered a film in our current motion picture industry, it was a huge step towards complete motion pictures. It is arguable that it is basic but it still remains that it was displayed as a wide angle as both the rider and horse are fully visible in the frame. After this innovation, in the 1880s celluloid photographic film and motion picture cameras became available so more motion pictures could be created in the form of Kinetoscope or through projectors. These early films also maintained a wide angle layout as it was the best way to keep everything visible for the viewer, once motion pictures became more available in the 1890s there were public screenings of many different films only being around a minute long, or even less. These films again adhered to the wide shot style, one of the first competitive filming techniques came in the form of the close-up as George Albert Smith incorporated them into his film Hove. Though unconfirmed as the first usage of this method it is one of the earliest recorded examples, once the introduction of new framing techniques were introduced then more and more were made and used for their benefits that they could provide that wide shots couldn’t. This was the point at which motion pictures evolved from short, more and more cinematic techniques appeared, resulting in the wide shot being less commonly used. However, it remained as it is almost irreplaceable in what it can achieve. When television entered the home, it was seen as a hit to the cinema industry. This in turn resulted in films having to stay ahead of television by incorporating superior quality than that of a television and this was done by adding color but importantly it implemented the use of widescreen. Most modern films will use the different types of wide shots as they are a staple in filmmaking and are almost impossible to avoid unless deliberately chosen to. In the current climate of films, the quality of any given shot will appear with much better clarity which has given life to some incredible shots from modern cinema. There are a variety of ways of framing that are considered as being under the banner of Wide Shots, in the case of a person, head to toe. This usually achieves a clear representation of a character and can describe the surroundings as it is usually visible within the frame. This results in the audience having a desired view/opinion of the character or location, very wide shot – The subject is only just visible in the location
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Medium shot
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In film, a medium shot, mid shot, or waist shot is a camera angle shot from a medium distance. Medium shots are used when the subject in the shot is delivering information. It is also used in interviews and it is the most common shot in movies, and it usually follows the first establishing shots of a new scene or location. A normal lens that sees what the human eye see, is used for medium shots. The dividing line between what constitutes a long shot and medium shot is not definite, nor is the line between medium shot and close-up, in other texts, these partial views are called medium shots. In principal, the shot is what can be seen with the human eye in a single quick glance. Medium shots are divided into singles, group shots, over-the shoulders or two-shots, Filmmaking A to Z, The Guide to 35 Millimeter Filmmaking
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Point-of-view shot
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A point of view shot is a short film scene that shows what a character is looking at. It is usually established by being positioned between a shot of a looking at something, and a shot showing the characters reaction. The technique of POV is one of the foundations of film editing, a POV shot need not be the strict point-of-view of an actual single character in a film. Sometimes the point-of-view shot is taken over the shoulder of the character, sometimes a POV shot is shared, i. e. it represents the joint POV of two characters. Camera angles record the scene from a particular players viewpoint, the point-of-view is an objective angle, but since it falls between the objective and subjective angle, it should be placed in a separate category and given special consideration. A point-of-view shot is as close as a shot can approach a subjective shot—and still remain objective. The camera is positioned at the side of a subjective player—whose viewpoint is being depicted—so that the audience is given the impression they are standing cheek-to-cheek with the off-screen player. The viewer does not see the event through the players eyes and he sees the event from the players viewpoint, as if standing alongside him. Thus, the angle remains objective, since it is an unseen observer not involved in the action. —Joseph V. Mascelli, The Five Cs of Cinematography Supporting narrative elements are required to indicate the shot to the viewer as a POV shot and these may include shot sequencing, sound effects, visual effects and acting. When the leading actor is the subject of the POV it is known as the subjective viewpoint, the audience sees events through the leading actors eyes, as if they were experiencing the events themselves. Cameras were increasingly introduced into more difficult experiences, dick Barrymore, an early action filmmaker akin to Warren Miller, experimented with film cameras and counter weights mounted to a helmet. Barrymore could ski unencumbered while capturing footage of scenery and other skiers, though the unit was heavy relative to its manner of use, it was considered hands-free, and worked. On professional levels, the equipment is defined, expensive. However the race for hands-free POV cameras for use on a level has always faced problems. Gance wrote in the scenario that the camera defends itself as if it were Bonaparte himself. It is in the fortress and fights back and it clambers on the wall of snow and jumps down, as if it were human. Arms at the side of the camera as if the camera itself had arms, Camera K falls on the ground, struggles, gets up
37.
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
38.
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
39.
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
40.
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
41.
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
42.
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
43.
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
44.
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
45.
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
