A lorgnette is a pair of spectacles with a handle, used to hold them in place, rather than fitting over the ears or nose. The word lorgnette is derived from the French lorgner, to take a sidelong look at, Middle French, from lorgne, squinting, they became popularized by Englishman George Adams when he designed a practical case meant to be carried in the pocket. The lorgnette was used as a piece of jewelry, rather than to enhance vision. Fashionable ladies preferred them to spectacles; these were popular at masquerade parties and used at the opera. They were worn popularly in the 19th century; the lorgnette was employed as a prop and affectation by early 20th century trial lawyer Earl Rogers, one is featured on the front cover dust jacket of his biography, Final Verdict, by his daughter Adela Rogers St. Johns. Musée des Lunettes et Lorgnettes Pierre Marly Monocle
Opera is a form of theatre in which music has a leading role and the parts are taken by singers, but is distinct from musical theater. Such a "work" is a collaboration between a composer and a librettist and incorporates a number of the performing arts, such as acting, scenery and sometimes dance or ballet; the performance is given in an opera house, accompanied by an orchestra or smaller musical ensemble, which since the early 19th century has been led by a conductor. Opera is a key part of the Western classical music tradition. Understood as an sung piece, in contrast to a play with songs, opera has come to include numerous genres, including some that include spoken dialogue such as musical theater, Singspiel and Opéra comique. In traditional number opera, singers employ two styles of singing: recitative, a speech-inflected style and self-contained arias; the 19th century saw the rise of the continuous music drama. Opera originated in Italy at the end of the 16th century and soon spread through the rest of Europe: Heinrich Schütz in Germany, Jean-Baptiste Lully in France, Henry Purcell in England all helped to establish their national traditions in the 17th century.
In the 18th century, Italian opera continued to dominate most of Europe, attracting foreign composers such as George Frideric Handel. Opera seria was the most prestigious form of Italian opera, until Christoph Willibald Gluck reacted against its artificiality with his "reform" operas in the 1760s; the most renowned figure of late 18th-century opera is Wolfgang Amadeus Mozart, who began with opera seria but is most famous for his Italian comic operas The Marriage of Figaro, Don Giovanni, Così fan tutte, as well as Die Entführung aus dem Serail, The Magic Flute, landmarks in the German tradition. The first third of the 19th century saw the high point of the bel canto style, with Gioachino Rossini, Gaetano Donizetti and Vincenzo Bellini all creating works that are still performed, it saw the advent of Grand Opera typified by the works of Auber and Meyerbeer. The mid-to-late 19th century was a golden age of opera and dominated by Giuseppe Verdi in Italy and Richard Wagner in Germany; the popularity of opera continued through the verismo era in Italy and contemporary French opera through to Giacomo Puccini and Richard Strauss in the early 20th century.
During the 19th century, parallel operatic traditions emerged in central and eastern Europe in Russia and Bohemia. The 20th century saw many experiments with modern styles, such as atonality and serialism and Minimalism. With the rise of recording technology, singers such as Enrico Caruso and Maria Callas became known to much wider audiences that went beyond the circle of opera fans. Since the invention of radio and television, operas were performed on these mediums. Beginning in 2006, a number of major opera houses began to present live high-definition video transmissions of their performances in cinemas all over the world. Since 2009, complete performances are live streamed; the words of an opera are known as the libretto. Some composers, notably Wagner, have written their own libretti. Traditional opera referred to as "number opera", consists of two modes of singing: recitative, the plot-driving passages sung in a style designed to imitate and emphasize the inflections of speech, aria in which the characters express their emotions in a more structured melodic style.
Vocal duets and other ensembles occur, choruses are used to comment on the action. In some forms of opera, such as singspiel, opéra comique and semi-opera, the recitative is replaced by spoken dialogue. Melodic or semi-melodic passages occurring in the midst of, or instead of, are referred to as arioso; the terminology of the various kinds of operatic voices is described in detail below. During both the Baroque and Classical periods, recitative could appear in two basic forms, each of, accompanied by a different instrumental ensemble: secco recitative, sung with a free rhythm dictated by the accent of the words, accompanied only by basso continuo, a harpsichord and a cello. Over the 18th century, arias were accompanied by the orchestra. By the 19th century, accompagnato had gained the upper hand, the orchestra played a much bigger role, Wagner revolutionized opera by abolishing all distinction between aria and recitative in his quest for what Wagner termed "endless melody". Subsequent composers have tended to follow Wagner's example, though some, such as Stravinsky in his The Rake's Progress have bucked the trend.
The changing role of the orchestra in opera is described in more detail below. The Italian word opera means "work", both in the sense of the labour done and the result produced; the Italian word derives from the Latin opera, a singular noun meaning "work" and the plural of the noun opus. According to the Oxford English Dictionary, the Italian word was first used in the sense "composition in which poetry and music are combined" in 1639. Dafne by Jacopo Peri was the earliest composition considered opera, it was writt
Nacre known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer. It is strong and iridescent. Nacre is found in some of the most ancient lineages of bivalves and cephalopods. However, the inner layer in the great majority of mollusc shells is porcellaneous, not nacreous, this results in a non-iridescent shine, or more in non-nacreous iridescence such as flame structure as is found in conch pearls; the outer layer of pearls and the inside layer of pearl oyster and freshwater pearl mussel shells are made of nacre. Other mollusc families that have a nacreous inner shell layer include marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae. Nacre is composed of hexagonal platelets of aragonite 10–20 µm wide and 0.5 µm thick arranged in a continuous parallel lamina. Depending on the species, the shape of the tablets differ. Whatever the shape of the tablets, the smallest units they contain are irregular rounded granules.
These layers are separated by sheets of organic matrix composed of elastic biopolymers. This mixture of brittle platelets and the thin layers of elastic biopolymers makes the material strong and resilient, with a Young's modulus of 70 GPa. Strength and resilience are likely to be due to adhesion by the "brickwork" arrangement of the platelets, which inhibits transverse crack propagation; this structure, at multiple length sizes increases its toughness, making it as strong as silicon. The statistical variation of the platelets has a negative effect on the mechanical performance because statistical variation precipitates localization of deformation. However, the negative effects of statistical variations can be offset by interfaces with large strain at failure accompanied by strain hardening. On the other hand, the fracture toughness of nacre increases with moderate statistical variations which creates tough regions where the crack gets pinned. But, higher statistical variations generates weak regions which allows the crack to propagate without much resistance causing the fracture toughness decreases.
Nacre appears iridescent because the thickness of the aragonite platelets is close to the wavelength of visible light. These structures interfere constructively and destructively with different wavelengths of light at different viewing angles, creating structural colours; the crystallographic c-axis points perpendicular to the shell wall, but the direction of the other axes varies between groups. Adjacent tablets have been shown to have different c-axis orientation randomly oriented within ~20° of vertical. In bivalves and cephalopods, the b-axis points in the direction of shell growth, whereas in the monoplacophora it is the a-axis, this way inclined; the interlocking of bricks of nacre has large impact on both the deformation mechanism as well as its toughness. In addition, the mineral–organic interface results in enhanced resilience and strength of the organic interlayers. Nacre formation is not understood; the initial onset assembly, as observed in Pinna nobilis, is driven by the aggregation of nanoparticles within an organic matrix that arrange in fibre-like polycrystalline configurations.
The particle number increases successively and, when critical packing is reached, they merge into early-nacre platelets. Nacre growth is mediated by organics, controlling the onset and form of crystal growth. Individual aragonite "bricks" are believed to grow to the full height of the nacreous layer, expand until they abut adjacent bricks; this produces the hexagonal close-packing characteristic of nacre. Bricks may nucleate on randomly dispersed elements within the organic layer, well-defined arrangements of proteins, or may grow epitaxially from mineral bridges extending from the underlying tablet. Nacre differs from fibrous aragonite – a brittle mineral of the same form – in that the growth in the c-axis is slow in nacre, fast in fibrous aragonite. Nacre is secreted by the epithelial cells of the mantle tissue of various molluscs; the nacre is continuously deposited onto the inner surface of the shell, the iridescent nacreous layer known as mother of pearl. The layers of nacre smooth the shell surface and help defend the soft tissues against parasites and damaging debris by entombing them in successive layers of nacre, forming either a blister pearl attached to the interior of the shell, or a free pearl within the mantle tissues.
The process is called encystation and it continues as long as the mollusc lives. The form of nacre varies from group to group. In bivalves, the nacre layer is formed of single crystals in a hexagonal close packing. In gastropods, crystals are twinned, in cephalopods, they are pseudohexagonal monocrystals, which are twinned; the main commercial sources of mother of pearl have been the pearl oyster, freshwater pearl mussels, to a lesser extent the abalone, popular for their sturdiness and beauty in the latter half of the 19th century. Used for pearl buttons during the 1900s, were the shells of the great green turban snail Turbo marmoratus and the large top snail, Tectus niloticus; the international trade in mother of pearl is governed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, an agreement signed by more than 170 countries. Nacre has been used for centuries for a variety o
Field of view
The field of view is the extent of the observable world, seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. In the context of human vision, the term "field of view" is only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles or virtual reality goggles. Note that eye movements are allowed in the definition but do not change the field of view. If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human is the visual field, it is defined as "the number of degrees of visual angle during stable fixation of the eyes". Note that eye movements are excluded in the definition. Different animals have different visual fields, among others, on the placement of the eyes. Humans have a over 210-degree forward-facing horizontal arc of their visual field, while some birds have a complete or nearly complete 360-degree visual field.
The vertical range of the visual field in humans is around 150 degrees. The range of visual abilities is not uniform across the visual field, varies from animal to animal. For example, binocular vision, the basis for stereopsis and is important for depth perception, covers 114 degrees of the visual field in humans; some birds have a scant 20 degrees of binocular vision. Color vision and the ability to perceive shape and motion vary across the visual field; the physiological basis for, the much higher concentration of color-sensitive cone cells and color-sensitive parvocellular retinal ganglion cells in the fovea – the central region of the retina, together with a larger representation in the visual cortex – in comparison to the higher concentration of color-insensitive rod cells and motion-sensitive magnocellular retinal ganglion cells in the visual periphery, smaller cortical representation. Since cone cells require brighter light sources to be activated, the result of this distribution is further that peripheral vision is much more sensitive at night relative to foveal vision.
Many optical instruments binoculars or spotting scopes, are advertised with their field of view specified in one of two ways: angular field of view, linear field of view. Angular field of view is specified in degrees, while linear field of view is a ratio of lengths. For example, binoculars with a 5.8 degree field of view might be advertised as having a field of view of 102 mm per meter. As long as the FOV is less than about 10 degrees or so, the following approximation formulas allow one to convert between linear and angular field of view. Let A be the angular field of view in degrees. Let M be the linear field of view in millimeters per meter. Using the small-angle approximation: A ≈ 360 ∘ 2 π ⋅ M 1000 ≈ 0.0573 × M M ≈ 2 π ⋅ 1000 360 ∘ ⋅ A ≈ 17.45 × A In machine vision the lens focal length and image sensor size sets up the fixed relationship between the field of view and the working distance. Field of view is the area of the inspection captured on the camera’s imager; the size of the field of view and the size of the camera’s imager directly affect the image resolution.
Working distance is the distance between the back of the target object. In remote sensing, the solid angle through which a detector element is sensitive to electromagnetic radiation at any one time, is called instantaneous field of view or IFOV. A measure of the spatial resolution of a remote sensing imaging system, it is expressed as dimensions of visible ground area, for some known sensor altitude. Single pixel IFOV is related to concept of resolved pixel size, ground resolved distance, ground sample distance and modulation transfer function. In astronomy, the field of view is expressed as an angular area viewed by the instrument, in square degrees, or for higher magnification instruments, in square arc-minutes. For reference the Wide Field Channel on the Advanced Camera for Surveys on the Hubble Space Telescope has a field of view of 10 sq. arc-minutes, the High Resolution Channel of the same instrument has a field of view of 0.15 sq. arc-minutes. Ground-based survey telescopes have much wider fields of view.
The photographic plates used by the UK Schmidt Telescope had a field of view of 30 sq. degrees. The 1.8 m Pan-STARRS telescope, with the most advanced digital camera to date has a field of view of 7 sq. degrees. In the near infra-red WFCAM on UKIRT has a field of view of 0.2 sq. degrees and the VISTA telescope has a field of view of 0.6 sq. degrees. Until digital cameras could only cover a small field of view compared to photographic plates, although they beat photographic plates in quantum efficiency
Binoculars or field glasses are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes when viewing distant objects. Most are sized to be held using both hands, although sizes vary from opera glasses to large pedestal mounted military models. Unlike a telescope, binoculars give users a three-dimensional image: for nearer objects the two views, presented to each of the viewer's eyes from different viewpoints, produce a merged view with an impression of depth. From the invention of the telescope in the 17th century the advantages of mounting two of them side by side for binocular vision seems to have been explored. Most early binoculars used Galilean optics; the Galilean design has the advantage of presenting an erect image but has a narrow field of view and is not capable of high magnification. This type of construction is still used in cheap models and in opera glasses or theater glasses; the Galilean design is used in low magnification binocular surgical and jewelers' loupes because they can be short and produce an upright image without extra or unusual erecting optics, reducing expense and overall weight.
They have large exit pupils making centering less critical and the narrow field of view works well in those applications. These are mounted on an eyeglass frame or custom-fit onto eyeglasses. An improved image and higher magnification is achieved in binoculars employing Keplerian optics, where the image formed by the objective lens is viewed through a positive eyepiece lens. Since the Keplerian configuration produces an inverted image, different methods are used to turn the image right way up. In aprismatic binoculars with Keplerian optics each tube has one or two additional lenses between the objective and the ocular; these lenses are used to erect the image. The binoculars with erecting lenses had a serious disadvantage: they are too long; such binoculars were popular in the 1800s, but became obsolete shortly after the Karl Zeiss company introduced improved prism binoculars in the 1890s. Optical prisms added to the design are another way to turn the image right way up in a Porro prism or roof-prisms design.
Porro prism binoculars are named after Italian optician Ignazio Porro who patented this image erecting system in 1854, refined by makers like the Carl Zeiss company in the 1890s. Binoculars of this type use a pair of Porro prisms in a Z-shaped configuration to erect the image; this results in binoculars that are wide, with objective lenses that are well separated and offset from the eyepieces, giving a better sensation of depth. Porro prism designs have the added benefit of folding the optical path so that the physical length of the binoculars is less than the focal length of the objective. Binoculars using roof prisms may have appeared as early as the 1870s in a design by Achille Victor Emile Daubresse. In 1897 Moritz Hensoldt began marketing roof prism binoculars. Most roof prism binoculars use either the Abbe-Koenig prism or the Schmidt-Pechan prism designs to erect the image and fold the optical path, they have objective lenses that are in line with the eyepieces. Roof-prisms designs create an instrument, narrower and more compact than Porro prisms.
There is a difference in image brightness. Porro-prism binoculars will inherently produce a brighter image than Schmidt-Pechan roof-prism binoculars of the same magnification, objective size, optical quality, because this roof-prism design employs silvered surfaces that reduce light transmission by 12% to 15%. Roof-prisms designs require tighter tolerances for alignment of their optical elements; this adds to their expense since the design requires them to use fixed elements that need to be set at a high degree of collimation at the factory. Porro prisms binoculars need their prism sets to be re-aligned to bring them into collimation; the fixed alignment in roof-prism designs means the binoculars will not need re-collimation. Binoculars are designed for specific applications; these different designs require certain optical parameters which may be listed on the prism cover plate of the binoculars. Those parameters are: Given as the first number in a binocular description, magnification is the ratio of the focal length of the objective divided by the focal length of the eyepiece.
This gives the magnifying power of binoculars. A magnification factor of 7, for example, produces an image 7 times larger than the original seen from that distance; the desirable amount of magnification depends upon the intended application, in most binoculars is a permanent, non-adjustable feature of the device. Hand-held binoculars have magnifications ranging from 7x to 10x, so they will be less susceptible to the effects of shaking hands. A larger magnification leads to a smaller field of view and may require a tripod for image stability; some specialized binoculars for astronomy or military use have magnifications ranging from 15x to 25x. Given as the second number in a binocular description, the diameter of the objective lens determines the resolution and how much light can be gathered to form an image; when two different binoculars have equal magnification, equal quality, produce a sufficiently matched exit pupil, the larger objective diameter produces a "brighter" and sharper