1.
Flange focal distance
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For an interchangeable lens camera, the flange focal distance of a lens mount system is the distance from the mounting flange to the film plane. This value is different for different camera systems, the range of this distance which will render an image clearly in focus within all focal lengths is usually measured in hundredths of millimeters and is known as the depth of focus. This distance influences whether a lens from one system can be mounted with an adaptor to a body of another system. Camera systems with a large flange-to-film distance have lenses that can be widely adapted, if the difference is small, other factors, such as the diameters of the mounting flanges of the two systems, come into play as well. Lens adapters are generally easier to make when the body has a large lens mount. Professional movie cameras are rigorously tested by rental houses regularly to ensure the distance is properly calibrated, the most common mount is the Arri PL mount with an FFD of 52.00 mm. List of lens mounts Markerink, Willem-Jan
2.
Optics
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Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light, because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for using the classical description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice, practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines, physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that waves were in fact electromagnetic radiation. Some phenomena depend on the fact that light has both wave-like and particle-like properties, explanation of these effects requires quantum mechanics. When considering lights particle-like properties, the light is modelled as a collection of particles called photons, quantum optics deals with the application of quantum mechanics to optical systems. Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics. Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, the earliest known lenses, made from polished crystal, often quartz, date from as early as 700 BC for Assyrian lenses such as the Layard/Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses, the word optics comes from the ancient Greek word ὀπτική, meaning appearance, look. Greek philosophy on optics broke down into two opposing theories on how vision worked, the theory and the emission theory. The intro-mission approach saw vision as coming from objects casting off copies of themselves that were captured by the eye, plato first articulated the emission theory, the idea that visual perception is accomplished by rays emitted by the eyes. He also commented on the parity reversal of mirrors in Timaeus, some hundred years later, Euclid wrote a treatise entitled Optics where he linked vision to geometry, creating geometrical optics. Ptolemy, in his treatise Optics, held a theory of vision, the rays from the eye formed a cone, the vertex being within the eye. The rays were sensitive, and conveyed back to the observer’s intellect about the distance. He summarised much of Euclid and went on to describe a way to measure the angle of refraction, during the Middle Ages, Greek ideas about optics were resurrected and extended by writers in the Muslim world
3.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
4.
Collimated light
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Collimated light is light whose rays are parallel, and therefore will spread minimally as it propagates. A perfectly collimated beam, with no divergence, would not disperse with distance, such a beam cannot be created, due to diffraction. Light can be collimated by a number of processes, for instance by means of a collimator. Perfectly collimated light is said to be focused at infinity. Thus, as the distance from a point source increases, the spherical wavefronts become flatter and closer to plane waves, the word collimate comes from the Latin verb collimare, which originated in a misreading of collineare, to direct in a straight line. In practice, gas lasers can use concave mirrors, flat mirrors, the divergence of high-quality laser beams is commonly less than 1 milliradian, and can be much less for large-diameter beams. Laser diodes emit less-collimated light due to their short cavity, synchrotron light is very well collimated. It is produced by bending relativistic electrons around a circular track, when the electrons are at relativistic speeds, the resulting radiation is highly collimated, a result which does not occur at slower speeds. The light from stars can be considered collimated for almost any purpose, because they are so far away they have almost no angular size, light from the Sun is nearly collimated by the time it reaches Earth because of its distance from the Earth. A perfect parabolic mirror will bring parallel rays to a focus at a single point, conversely, a point source at the focus of a parabolic mirror will produce a beam of collimated light creating a Collimator. Since the source needs to be small, such a system cannot produce much optical power. Spherical mirrors are easier to make than parabolic mirrors and they are used to produce approximately collimated light. Many types of lenses can also produce collimated light from point-like sources and this principle is used in full flight simulators, that have specially designed systems for displaying imagery of the Out-The-Window scene to the pilots in the replica aircraft cabin. Collimation refers to all the elements in an instrument being on their designed optical axis. It also refers to the process of adjusting an optical instrument so that all its elements are on that designed axis. With regards to a telescope, the term refers to the fact that the axis of each optical component should be centered and parallel. Most amateur reflector telescopes need to be re-collimated every few years to maintain optimum performance, collimation can also be tested using a shearing interferometer, which is often used to test laser collimation. Decollimation is any mechanism or process which causes a beam with the minimum possible ray divergence to diverge or converge from parallelism, decollimation must be accounted for to fully treat many systems such as radio, radar, sonar, and optical communications
5.
Focus (optics)
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In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent and this non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, aberrations tend to get worse as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, the border between these is sometimes defined using a circle of confusion criterion. A principal focus or focal point is a focus, For a lens, or a spherical or parabolic mirror. Since light can pass through a lens in either direction, a lens has two focal points—one on each side, the distance in air from the lens or mirrors principal plane to the focus is called the focal length. Elliptical mirrors have two points, light that passes through one of these before striking the mirror is reflected such that it passes through the other. The focus of a mirror is either of two points which have the property that light from one is reflected as if it came from the other. Diverging lenses and convex mirrors do not focus a beam to a point. Instead, the focus is the point from which the light appears to be emanating, a convex elliptical mirror will reflect light directed towards one focus as if it were radiating from the other focus, both of which are behind the mirror. A convex hyperbolic mirror will reflect rays emanating from the point in front of the mirror as if they were emanating from the focal point behind the mirror. Conversely, it can focus rays directed at the point that is behind the mirror towards the focal point that is in front of the mirror as in a Cassegrain telescope. Autofocus Cardinal point Defocus aberration Depth of field Depth of focus Far point Focus Fixed focus Bokeh Focus stacking Focal Plane
6.
Ray (optics)
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In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow. This allows even very complex systems to be analyzed mathematically or simulated by computer. Ray theory does not describe phenomena such as interference and diffraction, a light ray is a line that is perpendicular to the lights wavefronts, its tangent is collinear with the wave vector. Light rays in homogeneous media are straight and they bend at the interface between two dissimilar media and may be curved in a medium in which the refractive index changes. Geometric optics describes how rays propagate through an optical system, objects to be imaged are treated as collections of independent point sources, each producing spherical wavefronts and corresponding outward rays. Rays from each point can be mathematically propagated to locate the corresponding point on the image. There are many special rays that are used in modelling to analyze an optical system. These are defined and described below, grouped by the type of system they are used to model, an incident ray is a ray of light that strikes a surface. The angle between this ray and the perpendicular or normal to the surface is the angle of incidence, the reflected ray corresponding to a given incident ray, is the ray that represents the light reflected by the surface. The angle between the normal and the reflected ray is known as the angle of reflection. The Law of Reflection says that for a surface, the angle of reflection always equals the angle of incidence. The refracted ray or transmitted ray corresponding to an incident ray represents the light that is transmitted through the surface. The angle between this ray and the normal is known as the angle of refraction, and it is given by Snells Law. Conservation of energy requires that the power in the incident ray must equal the sum of the power in the ray, the power in the reflected ray. If the material is birefringent, the ray may split into ordinary and extraordinary rays. A meridional ray or tangential ray is a ray that is confined to the containing the systems optical axis. A skew ray is a ray that does not propagate in a plane that contains both the point and the optical axis. Such rays do not cross the optical axis anywhere, and are not parallel to it
7.
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
8.
Telescopy
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A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
9.
Magnification
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Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a number also called magnification. When this number is less one, it refers to a reduction in size. Typically, magnification is related to scaling up visuals or images to be able to see detail, increasing resolution, using microscope, printing techniques. In all cases, the magnification of the image does not change the perspective of the image, some optical instruments provide visual aid by magnifying small or distant subjects. A magnifying glass, which uses a lens to make things look bigger by allowing the user to hold them closer to their eye. A microscope, which makes an object appear as a much larger image at a comfortable distance for viewing. A microscope is similar in layout to a telescope except that the object being viewed is close to the objective, a slide projector, which projects a large image of a small slide on a screen. Optical magnification is the ratio between the apparent size of an object and its size, and thus it is a dimensionless number. Optical magnification is sometimes referred to as power, although this can lead to confusion with optical power, for real images, such as images projected on a screen, size means a linear dimension. For optical instruments with an eyepiece, the dimension of the image seen in the eyepiece cannot be given. Strictly speaking, one should take the tangent of that angle, example, The angular size of the full moon is 0. 5°. In binoculars with 10x magnification it appears to subtend an angle of 5°, the linear magnification of a thin lens is where f is the focal length and d o is the distance from the lens to the object. Note that for real images, M is negative and the image is inverted, for virtual images, M is positive and the image is upright. The image recorded by a film or image sensor is always a real image and is usually inverted. When measuring the height of an image using the cartesian sign convention the value for hi will be negative. However, the sign convention used in photography is real is positive. Therefore in photography, Object height and distance are always real, when the focal length is positive the images height, distance and magnification are real and positive
10.
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
11.
Microscopy
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Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. There are three branches of microscopy, optical, electron, and scanning probe microscopy. This process may be carried out by irradiation of the sample or by scanning of a fine beam over the sample. Scanning probe microscopy involves the interaction of a probe with the surface of the object of interest. The development of microscopy revolutionized biology, gave rise to the field of histology and so remains an essential technique in the life and physical sciences. Optical or light microscopy involves passing visible light transmitted through or reflected from the sample through a single or multiple lenses to allow a view of the sample. The resulting image can be detected directly by the eye, imaged on a plate or captured digitally. The single lens with its attachments, or the system of lenses and imaging equipment, along with the lighting equipment, sample stage and support. The most recent development is the microscope, which uses a CCD camera to focus on the exhibit of interest. The image is shown on a screen, so eye-pieces are unnecessary. Limitations of standard optical microscopy lie in three areas, This technique can only image dark or strongly refracting objects effectively, diffraction limits resolution to approximately 0.2 micrometres. This limits the practical limit to ~1500x. Out of focus light from points outside the focal plane reduces image clarity, live cells in particular generally lack sufficient contrast to be studied successfully, since the internal structures of the cell are colourless and transparent. The most common way to increase contrast is to stain the different structures with selective dyes, staining may also introduce artifacts, apparent structural details that are caused by the processing of the specimen and are thus not legitimate features of the specimen. In general, these make use of differences in the refractive index of cell structures. It is comparable to looking through a window, you dont see the glass. There is a difference, as glass is a material. The human eye is not sensitive to this difference in phase, in order to improve specimen contrast or highlight certain structures in a sample special techniques must be used
12.
Thin lens
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In optics, a thin lens is a lens with a thickness that is negligible compared to the radii of curvature of the lens surfaces. Lenses whose thickness is not negligible are sometimes called thick lenses, the thin lens approximation ignores optical effects due to the thickness of lenses and simplifies ray tracing calculations. It is often combined with the approximation in techniques such as ray transfer matrix analysis. For a thin lens, d is much smaller one of the radii of curvature. In these conditions, the last term of the Lensmakers equation becomes negligible, here R1 is taken to be positive if the first surface is convex, and negative if the surface is concave. The signs are reversed for the surface of the lens, R2 is positive if the surface is concave. This is a sign convention, some authors choose different signs for the radii. Any ray that arrives at the lens after passing through the point on the front side. Any ray that passes through the center of the lens will not change its direction, by tracing these rays, the relationship between the object distance s and the image distance s′ can be shown to be 1 s +1 s ′ =1 f. In scalar wave optics a lens is a part which shifts the phase of the wave-front, mathematically this can be understood as a multiplication of the wave-front with the following function, exp
13.
Lens (optics)
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A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a piece of transparent material, while a compound lens consists of several simple lenses. Lenses are made from such as glass or plastic, and are ground. A lens can focus light to form an image, unlike a prism, devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. The word lens comes from the Latin name of the lentil, the genus of the lentil plant is Lens, and the most commonly eaten species is Lens culinaris. The lentil plant also gives its name to a geometric figure, the variant spelling lense is sometimes seen. While it is listed as a spelling in some dictionaries. The oldest lens artifact is the Nimrud lens, dating back 2700 years to ancient Assyria, david Brewster proposed that it may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight. Another early reference to magnification dates back to ancient Egyptian hieroglyphs in the 8th century BC, the earliest written records of lenses date to Ancient Greece, with Aristophanes play The Clouds mentioning a burning-glass. Some scholars argue that the evidence indicates that there was widespread use of lenses in antiquity. Such lenses were used by artisans for fine work, and for authenticating seal impressions, both Pliny and Seneca the Younger described the magnifying effect of a glass globe filled with water. The Viking lenses were capable of concentrating enough sunlight to ignite fires, between the 11th and 13th century reading stones were invented. Often used by monks to assist in illuminating manuscripts, these were primitive plano-convex lenses initially made by cutting a sphere in half. As the stones were experimented with, it was understood that shallower lenses magnified more effectively. Lenses came into use in Europe with the invention of spectacles. Spectacle makers created improved types of lenses for the correction of vision based more on knowledge gained from observing the effects of the lenses. With the invention of the telescope and microscope there was a deal of experimentation with lens shapes in the 17th. Opticians tried to construct lenses of varying forms of curvature, wrongly assuming errors arose from defects in the figure of their surfaces
14.
Camera lens
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A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple convex lens will suffice, in practice a compound made up of a number of optical lens elements is required to correct the many optical aberrations that arise. Some aberrations will be present in any lens system and it is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production. Typical rectilinear lenses can be thought of as improved pinhole lenses, as shown, a pinhole lens is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor. Here a pixel is the area of the detector exposed to light from a point on the object, making the pinhole smaller improves resolution, but reduces the amount of light captured. At a certain point, shrinking the hole does not improve the resolution because of the diffraction limit, beyond this limit, making the hole smaller makes the image blurrier as well as darker. Practical lenses can be thought of as an answer to the question how can a pinhole lens be modified to more light. A first step is to put a simple convex lens at the pinhole with a length equal to the distance to the film plane. The geometry is almost the same as with a pinhole lens. From the front of the camera, the hole, would be seen. If one were inside the camera, one would see the acting as a projector. The virtual image of the aperture from inside the camera is the exit pupil. Practical photographic lenses include more lens elements, a camera lens may be made from a number of elements, from one, as in the Box Brownies meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together, the front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flare, and surface reflectance, to minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there is always a compromise, the lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused, manufacturers call this different things, Nikon calls it CRC, Canon calls it a floating system, and Hasselblad and Mamiya call it FLE. Glass is the most common used to construct lens elements, due to its good optical properties
15.
Telescope
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A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
16.
Cardinal point (optics)
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In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the points, the principal points, and the nodal points. The only ideal system that has achieved in practice is the plane mirror. Cardinal points provide a way to simplify a system with many components. The cardinal points lie on the axis of the optical system. Each point is defined by the effect the optical system has on rays that pass through that point, the paraxial approximation assumes that rays travel at shallow angles with respect to the optical axis, so that sin θ ≈ θ and cos θ ≈1. Aperture effects are ignored, rays that do not pass through the stop of the system are not considered in the discussion below. The front focal point of a system, by definition, has the property that any ray that passes through it will emerge from the system parallel to the optical axis. The rear focal point of the system has the reverse property, the front and rear focal planes are defined as the planes, perpendicular to the optic axis, which pass through the front and rear focal points. An object infinitely far from the optical system forms an image at the focal plane. For objects a finite distance away, the image is formed at a different location, but rays that leave the object parallel to one another cross at the rear focal plane. A diaphragm or stop at the focal plane can be used to filter rays by angle, since. No matter where on the object the ray comes from, the ray will pass through the aperture as long as the angle at which it is emitted from the object is small enough. Note that the aperture must be centered on the axis for this to work as indicated. Using a sufficiently small aperture in the plane will make the lens telecentric. Similarly, the range of angles on the output side of the lens can be filtered by putting an aperture at the front focal plane of the lens. This is important for DSLR cameras having CCD sensors, the pixels in these sensors are more sensitive to rays that hit them straight on than to those that strike at an angle. A lens that does not control the angle of incidence at the detector will produce pixel vignetting in the images and this means that the lens can be treated as if all of the refraction happened at the principal planes
17.
Refractive index
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In optics, the refractive index or index of refraction n of a material is a dimensionless number that describes how light propagates through that medium. It is defined as n = c v, where c is the speed of light in vacuum, for example, the refractive index of water is 1.333, meaning that light travels 1.333 times faster in a vacuum than it does in water. The refractive index determines how light is bent, or refracted. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the angle for total internal reflection. This implies that vacuum has a index of 1. The refractive index varies with the wavelength of light and this is called dispersion and causes the splitting of white light into its constituent colors in prisms and rainbows, and chromatic aberration in lenses. Light propagation in absorbing materials can be described using a refractive index. The imaginary part then handles the attenuation, while the real part accounts for refraction, the concept of refractive index is widely used within the full electromagnetic spectrum, from X-rays to radio waves. It can also be used with wave phenomena such as sound, in this case the speed of sound is used instead of that of light and a reference medium other than vacuum must be chosen. Thomas Young was presumably the person who first used, and invented, at the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers. The ratio had the disadvantage of different appearances, newton, who called it the proportion of the sines of incidence and refraction, wrote it as a ratio of two numbers, like 529 to 396. Hauksbee, who called it the ratio of refraction, wrote it as a ratio with a fixed numerator, hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in the next years, others started using different symbols, n, m, and µ. For visible light most transparent media have refractive indices between 1 and 2, a few examples are given in the adjacent table. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, gases at atmospheric pressure have refractive indices close to 1 because of their low density. Almost all solids and liquids have refractive indices above 1.3, aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, for infrared light refractive indices can be considerably higher
18.
Image
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Images may be two-dimensional, such as a photograph or screen display, or three-dimensional, such as a statue or hologram. They may be captured by optical devices – such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water. The word image is used in the broader sense of any two-dimensional figure such as a map, a graph. A volatile image is one that only for a short period of time. This may be a reflection of an object by a mirror, a fixed image, also called a hard copy, is one that has been recorded on a material object, such as paper or textile by photography or any other digital process. A mental image exists in a mind, as something one remembers or imagines. The subject of an image need not be real, it may be a concept, such as a graph, function. For example, Sigmund Freud claimed to have dreamed purely in aural-images of dialogs, a still image is a single static image, as distinguished from a kinetic image. This phrase is used in photography, visual media and the industry to emphasize that one is not talking about movies. A film still is a taken on the set of a movie or television program during production. In literature, imagery is a picture which appeals to the senses. It can both be figurative and literal, a moving image is typically a movie or video, including digital video. It could also be an animated display such as a zoetrope, library of Congress – Format Descriptions for Still Images Image Processing – Online Open Research Group Legal Issues Regarding Images Image Copyright Case
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Radius of curvature (optics)
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Radius of curvature has specific meaning and sign convention in optical design. A spherical lens or mirror surface has a center of curvature located in either along or decentered from the local optical axis. The vertex of the surface is located on the local optical axis. The distance from the vertex to the center of curvature is the radius of curvature of the surface, the sign convention for the optical radius of curvature is as follows, If the vertex lies to the left of the center of curvature, the radius of curvature is positive. If the vertex lies to the right of the center of curvature, thus when viewing a biconvex lens from the side, the left surface radius of curvature is positive, and the right surface has a negative radius of curvature. Note however that in areas of other than design, other sign conventions are sometimes used. In particular, many physics textbooks use an alternate sign convention in which convex surfaces of lenses are always positive. Care should be taken when using formulas taken from different sources, optical surfaces with non-spherical profiles, such as the surfaces of aspheric lenses, also have a radius of curvature. If α1 and α2 are zero, then R is the radius of curvature and K is the conic constant, as measured at the vertex. The coefficients α i describe the deviation of the surface from the axially symmetric quadric surface specified by R and K. Radius of curvature Radius Base curve radius Cardinal point Vergence
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Sphere
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A sphere is a perfectly round geometrical object in three-dimensional space that is the surface of a completely round ball. This distance r is the radius of the ball, and the point is the center of the mathematical ball. The longest straight line through the ball, connecting two points of the sphere, passes through the center and its length is twice the radius. While outside mathematics the terms sphere and ball are used interchangeably. The ball and the share the same radius, diameter. The surface area of a sphere is, A =4 π r 2, at any given radius r, the incremental volume equals the product of the surface area at radius r and the thickness of a shell, δ V ≈ A ⋅ δ r. The total volume is the summation of all volumes, V ≈ ∑ A ⋅ δ r. In the limit as δr approaches zero this equation becomes, V = ∫0 r A d r ′, substitute V,43 π r 3 = ∫0 r A d r ′. Differentiating both sides of equation with respect to r yields A as a function of r,4 π r 2 = A. Which is generally abbreviated as, A =4 π r 2, alternatively, the area element on the sphere is given in spherical coordinates by dA = r2 sin θ dθ dφ. In Cartesian coordinates, the element is d S = r r 2 − ∑ i ≠ k x i 2 ∏ i ≠ k d x i, ∀ k. For more generality, see area element, the total area can thus be obtained by integration, A = ∫02 π ∫0 π r 2 sin θ d θ d φ =4 π r 2. In three dimensions, the volume inside a sphere is derived to be V =43 π r 3 where r is the radius of the sphere, archimedes first derived this formula, which shows that the volume inside a sphere is 2/3 that of a circumscribed cylinder. In modern mathematics, this formula can be derived using integral calculus, at any given x, the incremental volume equals the product of the cross-sectional area of the disk at x and its thickness, δ V ≈ π y 2 ⋅ δ x. The total volume is the summation of all volumes, V ≈ ∑ π y 2 ⋅ δ x. In the limit as δx approaches zero this equation becomes, V = ∫ − r r π y 2 d x. At any given x, a right-angled triangle connects x, y and r to the origin, hence, applying the Pythagorean theorem yields, thus, substituting y with a function of x gives, V = ∫ − r r π d x. Which can now be evaluated as follows, V = π − r r = π − π =43 π r 3
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Mirror
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This is different from other light-reflecting objects that do not preserve much of the original wave signal other than color and diffuse reflected light. The most familiar type of mirror is the mirror, which has a flat screen surface. Curved mirrors are used, to produce magnified or diminished images or focus light or simply distort the reflected image. Mirrors are commonly used for personal grooming or admiring oneself, decoration, Mirrors are also used in scientific apparatus such as telescopes and lasers, cameras, and industrial machinery. Most mirrors are designed for light, however, mirrors designed for other wavelengths of electromagnetic radiation are also used. The first mirrors used by people were most likely pools of dark, still water, the requirements for making a good mirror are a surface with a very high degree of flatness, and a surface roughness smaller than the wavelength of the light. The earliest manufactured mirrors were pieces of polished stone such as obsidian, examples of obsidian mirrors found in Anatolia have been dated to around 6000 BC. Mirrors of polished copper were crafted in Mesopotamia from 4000 BC, polished stone mirrors from Central and South America date from around 2000 BC onwards. In China, bronze mirrors were manufactured from around 2000 BC, some of the earliest bronze, Mirrors made of other metal mixtures such as copper and tin speculum metal may have also been produced in China and India. Mirrors of speculum metal or any precious metal were hard to produce and were owned by the wealthy. Stone mirrors often had poor reflectivity compared to metals, yet metals scratch or tarnish easily, depending upon the color, both often yielded reflections with poor color rendering. The poor image quality of ancient mirrors explains 1 Corinthians 13s reference to seeing as in a mirror, glass was a desirable material for mirrors. Because the surface of glass is smooth, it produces reflections with very little blur. In addition, glass is very hard and scratch resistant, however, glass by itself has little reflectivity, so people began coating it with metals to increase the reflectivity. According to Pliny, the people of Sidon developed a technique for creating crude mirrors by coating glass with molten lead. Glass mirrors backed with gold leaf are mentioned by Pliny in his Natural History and these circular mirrors were typically small, from only a fraction of an inch to as much as eight inches in diameter. These small mirrors produced distorted images, yet were prized objects of high value and these ancient glass mirrors were very thin, thus very fragile, because the glass needed to be extremely thin to prevent cracking when coated with a hot, molten metal. Due to the quality, high cost, and small size of these ancient glass mirrors
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Curved mirror
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A curved mirror is a mirror with a curved reflecting surface. The surface may be convex or concave. Most curved mirrors have surfaces that are shaped like part of a sphere, one advantage that mirror optics have over lens optics is that mirrors do not introduce chromatic aberration. A convex mirror, fish eye mirror or diverging mirror, is a mirror in which the reflective surface bulges toward the light source. Convex mirrors reflect light outwards, therefore they are not used to focus light, such mirrors always form a virtual image, since the focal point and the centre of curvature are both imaginary points inside the mirror, that cannot be reached. As a result, images formed by these mirrors cannot be projected on a screen, the image is smaller than the object, but gets larger as the object approaches the mirror. A collimated beam of light diverges after reflection from a convex mirror, the passenger-side mirror on a car is typically a convex mirror. In some countries, these are labeled with the safety warning Objects in mirror are closer than they appear, convex mirrors are preferred in vehicles because they give an upright, though diminished, image. Also they provide a field of view as they are curved outwards. These mirrors are often found in the hallways of buildings, including hospitals, hotels, schools, stores. They are usually mounted on a wall or ceiling where hallways intersect each other and they are useful for people accessing the hallways, especially at locations having blind spots or where visibility may be limited. They are also used on roads, driveways, and alleys to provide safety for motorists where there is a lack of visibility, especially at curves and turns. Convex mirrors are used in automated teller machines as a simple and handy security feature. Similar devices are sold to be attached to ordinary computer monitors, convex mirrors make everything seem smaller but cover a larger area of surveillance. Round convex mirrors called Oeil de Sorcière were a luxury item from the 15th century onwards. With 15th century technology, it was easier to make a curved mirror than a perfectly flat one. They were also known as bankers eyes due to the fact that their field of vision was useful for security. Famous examples in art include the Arnolfini Portrait by Jan van Eyck, the image on a convex mirror is always virtual, diminished, and upright
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135 film
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135 is photographic film in a film format used for still photography. It is a film with a film gauge of 35 mm. Its engineering standard for the film is controlled by ISO1007, the term 135 was introduced by Kodak in 1934 as a designation for the cassette for 35 mm film, specifically for still photography. It quickly grew in popularity, surpassing 120 film by the late 1960s to become the most popular photographic film size, despite competition from formats such as 828,126,110, and APS, it remains so today. 135 camera film always comes perforated with Kodak Standard perforations, the size of the 135 film frame has been adopted by many high-end digital single-lens reflex and digital mirrorless cameras, commonly referred to as full frame. Even though the format is smaller than historical medium format and large format film, it is much larger than image sensors in most compact cameras. Individual rolls of 135 film are enclosed in single-spool, light-tight, the film is clipped or taped to a spool and exits via a slot lined with flocking. The end of the film is cut on one side to form a leader and it has the same dimensions and perforation pitch as 35 mm movie print film. Most cameras require the film to be rewound before the camera is opened, disposable cameras use the same technique so that the user does not have to rewind. Since the 1980s film cassettes have been marked with a DX encoding pattern, conforming cameras detect this, different films are sensitive to light at different degrees, this film speed is standardised by ISO.135 film has been made in several emulsion types and sensitivities. Since the introduction of digital cameras the most usual films have colour emulsions of ISO 100/21° to ISO 800/30°, films of lower sensitivity and higher sensitivity are for more specialist purposes. There are colour and monochrome films, negative and positive, monochrome film is usually panchromatic, orthochromatic has fallen out of use. Film designed to be sensitive to infrared radiation can be obtained, more exotic emulsions have been available in 135 than other roll-film sizes. The term 135 format usually refers to a 36×24 mm film format, the 36×24 mm format is common to digital image sensors, where it is typically referred to as full frame format. On 135 film, the dimension of the 36×24 mm frame runs parallel to the length of the film. The perforation size and pitch are according to the standard specification KS-1870, for each frame, the film advances 8 perforations. This is specified as 38.00 mm and this allows for 2 mm gaps between frames. Each camera model has a different location for the sprocket which advances the film, therefore, each camera model’s frame will vary in position relative to the perforations
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Rectilinear lens
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In photography, a rectilinear lens is a photographic lens that yields images where straight features, such as the walls of buildings, appear with straight lines, as opposed to being curved. In other words, it is a lens with little or no barrel or pincushion distortion, at particularly wide angles, however, the rectilinear perspective will cause objects to appear increasingly stretched and enlarged as they near the edge of the frame. These types of lenses are used to create forced perspective effects. The most famous example is the Rapid Rectilinear Lens developed by John Henry Dallmeyer in 1866 and it allowed distortionless photos to be taken quickly for the first time, and was a standard lens design for 60 years. The vast majority of video and still cameras use lenses that produce nearly rectilinear images, a popular alternative type of lens is a fisheye lens which produces a distinctly curvilinear, wide-angled result. Rectilinear grid Gnomonic projection Nikkor 13mm f/5.6 Michael R. Peres
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Normal lens
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In photography and cinematography, a normal lens is a lens that reproduces a field of view that appears natural to a human observer. Lenses with longer or shorter focal lengths produce an expanded or contracted field of view appears to distort the perspective when viewed from a normal viewing distance. Lenses of shorter focal length are called wide-angle lenses, while longer-focal-length lenses are referred to as long-focus lenses, such is the extent of distortions of perspective with these lenses that they may not be permitted as legal evidence. That is, the relationships of objects in the photograph should be equivalent to what they actually are. For cinematography, where the image is larger relative to viewing distance, the term normal lens can also be used as a synonym for rectilinear lens. This is a different use of the term. The 50 mm focal length was chosen by Oskar Barnack, the creator of the Leica camera. Note that the angle of view depends on the ratio as well. In digital photography, the type is not the sensor diameter. The normal lens focal length is roughly 2/3 of the TV tube diameter and this is a mathematical calculation because most of the cameras are equipped with zoom lenses
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35 mm film
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35 mm film is the film gauge most commonly used for motion pictures and chemical still photography. The name of the gauge refers to the width of the photographic film, the standard negative pulldown for movies is four perforations per frame along both edges, which results in 16 frames per foot of film. For still photography, the frame has eight perforations on each side. This resulted in cameras, projectors, and other equipment having to be calibrated to each gauge, the 35 mm width, originally specified as 1.375 inches, was introduced in 1892 by William Dickson and Thomas Edison, using film stock supplied by George Eastman. The gauge has been versatile in application, Eastman Kodak, Fujifilm and Agfa-Gevaert are some companies which offered 35 mm films. Today Kodak is the last remaining manufacturer of motion picture film and it is difficult to compare the quality of film to digital media but a good estimate would be about 20.8 million total pixels would equal one 35 millimeter high quality color frame of film. In 1880, George Eastman began to manufacture gelatin dry plates in Rochester. Along with W. H. Walker, Eastman invented a holder for a roll of picture-carrying gelatin layer coated paper, hannibal Goodwins invention of nitrocellulose film base in 1887 was the first transparent, flexible film. With the advent of film, Thomas Alva Edison quickly set out on his invention, the Kinetoscope. The Kinetoscope was a loop system intended for one-person viewing. Edison, along with assistant W. K. L. Dickson, followed that up with the Kinetophone, beginning in March 1892, Eastman and then, from April 1893 into 1896, New Yorks Blair Camera Co. supplied Edison with film stock. Edisons aperture defined a single frame of film at 4 perforations high, a court judgment in March 1902 invalidated Edisons claim, allowing any producer or distributor to use the Edison 35 mm film design without license. Filmmakers were already doing so in Britain and Europe, where Edison had failed to file patents, at the time, film stock was usually supplied unperforated and punched by the filmmaker to their standards with perforation equipment. A variation developed by the Lumière Brothers used a circular perforation on each side of the frame towards the middle of the horizontal axis.33 aspect ratio. Spehr describes the importance of these developments, The early acceptance of 35 mm as a standard had momentous impact on the development and spread of cinema. The film format was introduced into still photography as early as 1913 but first became popular with the launch of the Leica camera, created by Oskar Barnack in 1925. The costly image-forming silver compounds in a film stocks emulsion meant from the start that 35 mm filmmaking was to be a hobby with a high barrier to entry for the public at large. Furthermore, the film base of all early film stock was highly flammable
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Pinhole camera
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A pinhole camera is a simple camera without a lens but with a tiny aperture, a pinhole – effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an image on the opposite side of the box. It is based on property of light Camera obscura or pinhole images are an optical phenomenon. Early known descriptions are found in the Chinese Mozi writings and the Aristotelian Problems, starting with Alhazen the effect was used in dark rooms, mostly to study the nature of light and to safely watch sun eclipses. Giambattista della Porta wrote in 1558 in his Magia Naturalis about using a mirror to project the image onto paper. However, about the time the use of a lens instead of a pinhole was introduced. In the 17th century the camera obscura with a lens became a drawing aid that was further developed into a mobile device, first in a little tent. The photographic camera, as developed early in the 19th century, was basically, one older use of the term pin-hole in the context of optics was found in James Fergusons 1764 book Lectures on select subjects in mechanics, hydrostatics, pneumatics, and optics. Sir William Crookes and William de Wiveleslie Abney were other photographers to try the pinhole technique. The image of a camera may be projected onto a translucent screen for real-time viewing or to trace the image on paper. But it is often used without a translucent screen for pinhole photography with photographic film or photographic paper placed on the surface opposite to the pinhole aperture. A common use of photography is to capture the movement of the sun over a long period of time. This type of photography is called solargraphy, pinhole photography is used for artistic reasons, but also for educational purposes to let pupils learn about, and experiment with, the basics of photography. Pinhole cameras with CCDs are sometimes used for surveillance because they are difficult to detect, related cameras, image forming devices, or developments from it include Frankes widefield pinhole camera, the pinspeck camera, and the pinhead mirror. Pinhole photographs have nearly infinite depth of field, everything appears in focus, as theres no lens distortion, wide angle images remain absolutely rectilinear. Exposure times are long, resulting in motion blur around moving objects. Pinhole cameras can be handmade by the photographer for a particular purpose, in its simplest form, the photographic pinhole camera can consist of a light-tight box with a pinhole in one end, and a piece of film or photographic paper wedged or taped into the other end. A flap of cardboard with a hinge can be used as a shutter
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Distortion (optics)
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In geometric optics, distortion is a deviation from rectilinear projection, a projection in which straight lines in a scene remain straight in an image. It is a form of optical aberration, although distortion can be irregular or follow many patterns, the most commonly encountered distortions are radially symmetric, or approximately so, arising from the symmetry of a photographic lens. These radial distortions can usually be classified as either barrel distortions or pincushion distortions, mathematically, barrel and pincushion distortion are quadratic, meaning they increase as the square of distance from the center. Barrel distortion may be found in wide-angle lenses, and is seen at the wide-angle end of zoom lenses. Mustache distortion is observed particularly on the end of zooms, with certain retrofocus lenses. A certain amount of distortion is often found with visual optical instruments, e. g. binoculars. A graph showing radius transformations will be steeper in the upper end, conversely, barrel distortion is actually a diminished radius mapping for large radii in comparison with small radii. A graph showing radius transformations will be less steep in the upper end, radial distortion that depends on wavelength is called lateral chromatic aberration – lateral because radial, chromatic because dependent on color. This can cause colored fringes in high-contrast areas in the parts of the image. This should not be confused with axial chromatic aberration, which causes aberrations throughout the field, the names for these distortions come from familiar objects which are visually similar. Radial distortion, whilst primarily dominated by low order radial components, can be corrected using Browns distortion model, the Brown–Conrady model corrects both for radial distortion and for tangential distortion caused by physical elements in a lens not being perfectly aligned. The latter is known as decentering distortion. See Zhang for radial distortion discussion, barrel distortion typically will have a negative term for K1 whereas pincushion distortion will have a positive value. Moustache distortion will have a non-monotonic radial geometric series where for some r the sequence will change sign, software can correct those distortions by warping the image with a reverse distortion. This involves determining which distorted pixel corresponds to each undistorted pixel, lateral chromatic aberration can be significantly reduced by applying such warping for red, green and blue separately. An alternative method iteratively computes the undistorted pixel position, calibrated systems work from a table of lens/camera transfer functions, Adobe Photoshop Lightroom and Photoshop CS5 can correct complex distortion. PTlens is a Photoshop plugin or standalone application which corrects complex distortion and it not only corrects for linear distortion, but also second degree and higher nonlinear components. Lensfun is a free to use database and library for correcting lens distortion, dxO Labs Optics Pro can correct complex distortion, and takes into account the focus distance
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Pinhole camera model
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The model does not include, for example, geometric distortions or blurring of unfocused objects caused by lenses and finite sized apertures. It also does not take account that most practical cameras have only discrete image coordinates. This means that the camera model can only be used as a first order approximation of the mapping from a 3D scene to a 2D image. Its validity depends on the quality of the camera and, in general and this means that the pinhole camera model often can be used as a reasonable description of how a camera depicts a 3D scene, for example in computer vision and computer graphics. NOTE, The x1x2x3 coordinate system in the figure is left-handed, the geometry related to the mapping of a pinhole camera is illustrated in the figure. The figure contains the basic objects, A 3D orthogonal coordinate system with its origin at O. This is also where the aperture is located. The three axes of the system are referred to as X1, X2, X3. Axis X3 is pointing in the direction of the camera and is referred to as the optical axis, principal axis. The 3D plane which intersects with axes X1 and X2 is the front side of the camera, an image plane where the 3D world is projected through the aperture of the camera. The image plane is parallel to axes X1 and X2 and is located at distance f from the origin O in the direction of the X3 axis. A practical implementation of a pinhole camera implies that the plane is located such that it intersects the X3 axis at coordinate -f where f >0. F is also referred to as the length of the pinhole camera. A point R at the intersection of the axis and the image plane. This point is referred to as the point or image center. A point P somewhere in the world at coordinate relative to the axes X1, X2, the projection line of point P into the camera. This is the line which passes through point P and the point O. The projection of point P onto the plane, denoted Q
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Wide-angle lens
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In photography and cinematography, a wide-angle lens refers to a lens whose focal length is substantially smaller than the focal length of a normal lens for a given film plane. This exaggeration of size can be used to make foreground objects more prominent and striking. A wide angle lens is one that projects a substantially larger image circle than would be typical for a standard design lens of the same focal length. This large image circle enables either large tilt & shift movements with a view camera, by convention, in still photography, the normal lens for a particular format has a focal length approximately equal to the length of the diagonal of the image frame or digital photosensor. In cinematography, a lens of twice the diagonal is considered normal. A lens is considered wide-angle when it covers the angle of view between 64° and 84° which in return translates to 35–24mm lens in 35mm film format, longer lenses magnify the subject more, apparently compressing distance and blurring the background because of their shallower depth of field. Wider lenses tend to distance between objects while allowing greater depth of field. For a full-frame 35 mm camera with a 36 mm by 24 mm format, the diagonal measures 43.3 mm and by custom, also by custom, a lens of focal length 35 mm or less is considered wide-angle. Ultra wide angle lenses have a length shorter than the short side of the film or sensor. In 35 mm, an ultra wide-angle lens has a length shorter than 24 mm. Common wide-angle for a full-frame 35 mm camera are 35,28,24,21,20,18 and 14 mm, the latter four being ultra-wide. Many of the lenses in this range will produce a more or less rectilinear image at the film plane, Ultra wide-angle lenses that do not produce a rectilinear image are called fisheye lenses. Common focal lengths for these in a 35 mm camera are 6 to 8 mm. Lenses with focal lengths of 8 to 16 mm may be either rectilinear or fisheye designs, Wide-angle lenses come in both fixed-focal-length and zoom varieties. For 35 mm cameras, lenses producing rectilinear images can be found at lengths as short as 8 mm. As of 2015, many digital cameras have image sensors that are smaller than the film format of full-frame 35 mm cameras. The camera manufacturers provide a crop factor to show how much smaller the sensor is than a full 35 mm film frame, for example, one common factor is 1.5, although many cameras have crop factors of 1.6,1.7 and 2. As example, a 28 mm lens on the DSLR would produce the angle of view of a 42 mm lens on a full-frame camera. For example, to get the equivalent angle of view of a 30 mm lens on a full-frame 35 mm camera, from a camera with a 1.5 crop factor
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Telephoto lens
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In photography and cinematography, a telephoto lens is a specific type of a long-focus lens in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special group known as a telephoto group that extends the light path to create a long-focus lens in a much shorter overall design. The angle of view and other effects of long-focus lenses are the same for telephoto lenses of the same specified focal length, long-focal-length lenses are often informally referred to as telephoto lenses although this is technically incorrect, a telephoto lens specifically incorporates the telephoto group. In contrast to a lens, for any given focal length a simple lens of non-telephoto design is constructed from one lens. To focus on an object at infinity, the distance from this single lens to focal plane of the camera has to be adjusted to this focal length, for example, given a focal length of 500 mm, the distance between lens and focal plane is 500 mm. The farther the focal length is increased, the more the length of such a simple lens makes it unwieldy. But such simple lenses are not telephoto lenses, no matter how extreme the focal length – they are known as long-focus lenses, while the optical centre of a simple lens is within the construction, the telephoto lens moves the optical centre in front of the construction. The basic construction of a telephoto lens consists of front lens elements that, the focal length of this group is shorter than the effective focal length of the lens. The converging rays from this group are intercepted by the rear lens group, sometimes called the telephoto group, the simplest telephoto designs could consist of one element in each group, but in practice, more than one element is used in each group to correct for various aberrations. The combination of two groups produces a lens assembly that is physically shorter than a long-focus lens producing the same image size. This same property is achieved in camera lenses that combine mirrors with lenses and these designs, called catadioptric, reflex, or mirror lenses, have a curved mirror as the primary objective with some form of negative lens in front of the mirror to correct optical aberrations. They also use a secondary mirror to relay the image that extends the light cone the same way the negative lens telephoto group does. The mirrors also fold the light path, the heaviest non-Catadioptric telephoto lens for civilian use was made by Carl Zeiss and has a focal length of 1700 mm with a maximum aperture of f/4, implying a 425 mm entrance pupil. It is designed for use with a medium format Hasselblad 203 FE camera, the telephoto lens design has also been used for wide angles, at least once in the case of the Olympus XA where it permitted a 35mm focal length to fit in an extra compact camera body. Inverting the telephoto configuration, employing one or more negative lens groups in front of a positive lens group and this allows for greater clearance for other optical or mechanical parts such as the mirror parts in a single-lens reflex camera. Zoom lenses that are telephotos at one extreme of the zoom range, the concept of the telephoto lens, in reflecting form, was first described by Johannes Kepler in his Dioptrice of 1611, and re-invented by Peter Barlow in 1834. Some of his photographs are preserved in the holdings of the Turnbull Library in Wellington, one of McKay’s photographs shows the Russian warship Vjestnik anchored in Wellington harbour about two and a half kilometres away, with its rigging lines and gun ports clearly visible. The other, taken from the point, is of a local hotel
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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
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Full-frame digital SLR
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The term full frame is used by users of digital single-lens reflex cameras as a shorthand for an image sensor format which is the same size as 35mm format film. Historically, 35mm was considered a film format compared with medium format, large format. This is in contrast to cameras with smaller sensors, much smaller than a full 35mm frame. Currently, the majority of cameras, both compact and SLR models, use a smaller-than-35 mm frame, as it is easier and cheaper to manufacture imaging sensors at a smaller size. Historically, the earliest digital SLR models, such as the Nikon NASA F4 or Kodak DCS100, Kodak states that 35mm film has the equivalent of 6,000 pixel horizontal resolution according to a Senior Vice President of IMAX. If the lens mounts are compatible, many lenses, including manual-focus models, when a lens designed for a full-frame camera, whether film or digital, is mounted on a DSLR with a smaller sensor size, only the center of the lens image circle is captured. The edges are cropped off, which is equivalent to zooming in on the section of the imaging area. When used with lenses designed for full frame film or digital cameras full-frame DSLRs offer a number of advantages compared to their smaller-sensor counterparts, one advantage is that wide-angle lenses designed for full-frame 35mm retain that same wide angle of view. On smaller-sensor DSLRs, wide-angle lenses have smaller angles of view equivalent to those of longer-focal-length lenses on 35mm film cameras. For example, a 24 mm lens on a camera with a factor of 1.5 has a 62° diagonal angle of view. On a full-frame digital camera, the 24 mm lens has the same 84° angle of view as it would on a 35mm film camera, equivalently, for the same DoF, the full-frame format will require a larger f-number. There are optical quality implications as well—not only because the image from the lens is effectively cropped—but because many lens designs are now optimized for sensors smaller than 36 mm ×24 mm. The full-frame sensor can also be useful with wide-angle perspective control or tilt/shift lenses, in particular, for example, a 200 mm lens on a camera with a crop factor of 1. 5× has the same angle of view as a 300 mm lens on a full-frame camera. The extra reach, for a number of pixels, can be helpful in specific areas of photography such as wildlife or sports. Lower size sensors also allow for the use of a range of lenses. By only using the center of the lens, these impurities are not noticed, in practice, this allows for the use of lower cost glass without corresponding loss of quality. Finally, full frame sensors allow for sensor designs that result in noise levels at high ISO. Pixel density is lower on full frame sensors and this means the pixels can be either spaced further apart from each other, or each photodiode can be manufactured at a slightly larger size
34.
Digital camera
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A digital camera or digicam is a camera that produces digital images that can be stored in a computer, displayed on a screen and printed. Most cameras sold today are digital, and digital cameras are incorporated into many devices ranging from PDAs, Digital and movie cameras share an optical system, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film, however, unlike film cameras, digital cameras can display images on a screen immediately after being recorded, and store and delete images from memory. Many digital cameras can also record moving videos with sound, some digital cameras can crop and stitch pictures and perform other elementary image editing. The history of the camera began with Eugene F. Lally of the Jet Propulsion Laboratory. His 1961 idea was to take pictures of the planets and stars while travelling through space to give information about the astronauts position, unfortunately, as with Texas Instruments employee Willis Adcocks filmless camera in 1972, the technology had yet to catch up with the concept. Steven Sasson as an engineer at Eastman Kodak invented and built the first electronic camera using a charge-coupled device image sensor in 1975, earlier ones used a camera tube, later ones digitized the signal. Early uses were military and scientific, followed by medical. In the mid to late 1990s digital cameras became common among consumers, by the mid-2000s digital cameras had largely replaced film cameras, and higher-end cell phones had an integrated digital camera. By the beginning of the 2010s, almost all smartphones had a digital camera. The two major types of image sensor are CCD and CMOS. A CCD sensor has one amplifier for all the pixels, while each pixel in a CMOS active-pixel sensor has its own amplifier, compared to CCDs, CMOS sensors use less power. Cameras with a small sensor use a back-side-illuminated CMOS sensor, overall final image quality is more dependent on the image processing capability of the camera, than on sensor type. The resolution of a camera is often limited by the image sensor that turns light into that discrete signals. The brighter the image at a point on the sensor. Depending on the structure of the sensor, a color filter array may be used. The number of pixels in the sensor determines the cameras pixel count, in a typical sensor, the pixel count is the product of the number of rows and the number of columns. For example, a 1,000 by 1,000 pixel sensor would have 1,000,000 pixels, final quality of an image depends on all optical transformations in the chain of producing the image
35.
Crop factor
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In the case of digital cameras, the imaging device would be a digital sensor. The most commonly used definition of crop factor is the ratio of a 35 mm frames diagonal to the diagonal of the sensor in question. Given the same 3,2 aspect ratio as 35mms 36 mm ×24 mm area, this is equivalent to the ratio of heights or ratio of widths, the ratio of sensor areas is the square of the crop factor. If it is desired to capture an image with the field of view and image quality but different cameras. The term format factor is also used, and is a more neutral term that corresponds to the German word for this concept. Of course, the focal length of a photographic lens is fixed by its optical construction. Most DSLRs on the market have nominally APS-C-sized image sensors, smaller than the standard 36 ×24 mm film frame, for example, many Canon DSLRs use an APS-C sensor that measures 22.2 mm ×14.8 mm. Because of this crop, the field of view is reduced by a factor proportional to the ratio between the smaller sensor size and the 35 mm film format size. For most DSLR cameras, this factor is 1. 3–2. 0× and this narrowing of the FOV is a disadvantage to photographers when a wide FOV is desired. Ultra-wide lens designs become merely wide, wide-angle lenses become normal, however, the crop factor can be an advantage to photographers when a narrow FOV is desired. It allows photographers with long-focal-length lenses to fill the frame more easily when the subject is far away. A300 mm lens on a camera with a 1.6 crop factor delivers images with the same FOV that a 35 mm film camera would require a 480 mm long focus lens to capture. Due to the statistics of photon shot noise, the properties of signal-to-noise ratio. Since crop factor is proportional to the square root of sensor area. The larger sensor has the smaller crop factor and the higher signal-to-noise ratio, most SLR camera and lens manufacturers have addressed the concerns of wide-angle lens users by designing lenses with shorter focal lengths, optimized for the DSLR formats. In most cases, these lenses are designed to cast an image circle that would not cover a 24×36 mm frame. Because they cast an image circle, the lenses can be optimized to use less glass and are sometimes physically smaller and lighter than those designed for full-frame cameras. Such lenses usually project an image circle than lenses that were designed for the full-frame 35 mm format
36.
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
37.
F-number
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The f-number of an optical system such as a camera lens is the ratio of the systems focal length to the diameter of the entrance pupil. It is a number that is a quantitative measure of lens speed. It is also known as the ratio, f-ratio, f-stop. The f-number is commonly indicated using a hooked f with the format f/N, the f-number N or f# is given by, N = f D where f is the focal length, and D is the diameter of the entrance pupil. It is customary to write f-numbers preceded by f/, which forms a mathematical expression of the pupil diameter in terms of f and N. Ignoring differences in light transmission efficiency, a lens with a greater f-number projects darker images, the brightness of the projected image relative to the brightness of the scene in the lenss field of view decreases with the square of the f-number. Doubling the f-number decreases the brightness by a factor of four. To maintain the same photographic exposure when doubling the f-number, the time would need to be four times as long. Most lenses have a diaphragm, which changes the size of the aperture stop. The entrance pupil diameter is not necessarily equal to the aperture stop diameter, a 100 mm focal length f/4 lens has an entrance pupil diameter of 25 mm. A200 mm focal length f/4 lens has a pupil diameter of 50 mm. The 200 mm lenss entrance pupil has four times the area of the 100 mm lenss entrance pupil, a T-stop is an f-number adjusted to account for light transmission efficiency. The word stop is sometimes confusing due to its multiple meanings, a stop can be a physical object, an opaque part of an optical system that blocks certain rays. In photography, stops are also a used to quantify ratios of light or exposure. The one-stop unit is known as the EV unit. On a camera, the setting is traditionally adjusted in discrete steps. Each stop is marked with its corresponding f-number, and represents a halving of the light intensity from the previous stop. This corresponds to a decrease of the pupil and aperture diameters by a factor of 1/2 or about 0.7071, each element in the sequence is one stop lower than the element to its left, and one stop higher than the element to its right
38.
SPIE
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SPIE is an American not-for-profit professional society for optics and photonics technology, founded in 1955. SPIE is most known for Photonics West, held in San Francisco, the society publishes peer-reviewed scientific journals, conference proceedings, monographs, tutorial texts, field guides, and reference volumes in print and online. In 2015, the society provided more than $5.2 million in support of optics education, on July 1,1955 SPIE was founded as the Society of Photographic Instrumentation Engineers in California to specialize in the application of photographic instrumentation. In 1964 the society changed its name to the Society of Photo-Optical Instrumentation Engineers, in 1977 SPIE moved its headquarters to Bellingham, Washington, and in 1981 the Society began doing business as SPIE—The International Society for Optical Engineering to reflect a changing membership. In 2007, the society ended its DBA and is now referred to simply as SPIE, SPIE has members from around the world, including North and South America, Europe, Africa, and Asia, with central offices in North America and Europe. SPIE Conferences and Exhibitions connect optical science and the optics industry, the society is affiliated with over 140 meetings and events each year. The societys first publication, SPIE Newsletter, was launched in 1957, in 1959, the society published its first book, SPIE Photographic Instrumentation Catalog. The newsletter morphed into the society’s first journal, now known as Optical Engineering, throughout the years, SPIE has created many publications including journals, magazines, newspapers, websites, and books. SPIE publishes, Ten scientific online journals SPIE Technical Paper Proceedings At least 25 original technical books per year via SPIE Press All SPIE journals are peer-reviewed, journal of Applied Remote Sensing, is an online-only, quarterly published journal on remote sensing. Journal of Biomedical Optics, is published monthly with the latest on optical technology in health care, journal of Electronic Imaging, co-published bi-monthly with the Society for Imaging Science and Technology, publishes papers on electronic imaging science and technology. Optical Engineering, the monthly journal of the society, with papers on research and development in all areas of optics, photonics. Its origins date back to 1989 with the publication of The New Physical Optics Notebook, the SPIE Digital Library publishes online technical papers from SPIE Journals and Conference Proceedings from 1962 to the present, as well as eBooks published by SPIE Press. There are more than 450,000 articles with more than 18,000 new research papers added annually, RSS Feeds are available on different topics. SPIE started a new Open Access program January 2013 to promote knowledge transfer, education, All new articles published in SPIE journals for which authors pay voluntary page charges are freely accessible to anyone. The SPIE Career Center is a recruitment resource for companies and professionals in the optics and photonics community, candidates can post their CV/resume online, search the job board, and access additional resources for career advancement. Employers and recruiters can post their jobs online and conduct targeted resume searches, SPIE provides more than 1,100 educational courses and workshops in various formats including at SPIE conferences, online, via DVDs and videos, and in-company training courses. SPIE has been approved as a provider of Continuing Education Units by IACET, The International Association for Continuing Education. The societys membership includes more than 18,500 professionals, students and those distinguished through outstanding contributions in the relevant technologies are eligible for election as SPIE Fellows
39.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
40.
Addison-Wesley
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Addison-Wesley is a publisher of textbooks and computer literature. It is an imprint of Pearson PLC, a global publishing, in addition to publishing books, Addison-Wesley also distributes its technical titles through the Safari Books Online e-reference service. Addison-Wesleys majority of sales derive from the United States and Europe, the Addison-Wesley Professional Imprint produces content including books, eBooks, and video for the professional IT worker including developers, programmers, managers, system administrators. Classic titles include The Art of Computer Programming, The C++ Programming Language, The Mythical Man-Month, Addison-Wesley Professional is also a partner with Safari Books Online. Its first computer book was Programs for an Electronic Digital Computer, by Wilkes, Wheeler, in 1977, Addison-Wesley acquired W. A. Benjamin Company, and merged it with the Cummings division of the company to form Benjamin Cummings. It was purchased by the publishing and education company, Pearson PLC in 1988. The trade publishing division of Addison-Wesley was sold to Perseus Books Group in 1997, Pearson acquired the educational division of Simon & Schuster in 1998, and merged it with Addison Wesley Longman to form Pearson Education and subsequently rebranded to Pearson in 2011. Pearson moved the former Addison Wesley Longman offices from Reading, Massachusetts to Boston in 2004 and its current executives hail from the original Addison-Wesley with a storied history of their own. Addison-Wesley Secondary Math, An Integrated Approach, Focus on Algebra The Art of Computer Programming by Donald Knuth The Feynman Lectures on Physics by Richard Feynman, Robert B. Leighton, and Matthew Sands Concrete Mathematics, A Foundation For Computer Science by Ronald Graham, Donald Knuth, exploratory data analysis by John W. Tukey, based on a course taught at Princeton. The Mythical Man-Month by Fred P. Brooks
41.
Focal Press
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Focal Press is a publisher of media technology books and it is an imprint of Taylor & Francis. It was founded in 1938 by Andor Kraszna-Krausz, a Hungarian photographer who immigrated to England in 1937, Elsevier acquired Focal Press in 1983. Focal Press was acquired by Taylor & Francis from Elsevier in July 2012
42.
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
43.
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
44.
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
