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Roof Pentaprism
A pentaprism is a five-sided reflecting prism used to deviate a beam of light by a constant 90°, even if the entry beam is not at 90° to the prism. The beam reflects inside the prism ''twice'', allowing the transmission of an image through a right angle without inverting it (that is, without changing the image's handedness) as an ordinary right-angle prism or mirror would. The reflections inside the prism are not caused by total internal reflection, since the beams are incident at an angle less than the critical angle (the minimum angle for total internal reflection). Instead, the two faces are coated to provide mirror surfaces. The two opposite transmitting faces are often coated with an antireflection coating to reduce spurious reflections. The fifth face of the prism is not used optically but truncates what would otherwise be an awkward angle joining the two mirrored faces. In cameras A variant of this prism is the roof pentaprism which is commonly used in the viewfinde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaprism
A pentaprism is a five-sided reflecting prism used to deviate a beam of light by a constant 90°, even if the entry beam is not at 90° to the prism. The beam reflects inside the prism ''twice'', allowing the transmission of an image through a right angle without inverting it (that is, without changing the image's handedness) as an ordinary right-angle prism or mirror would. The reflections inside the prism are not caused by total internal reflection, since the beams are incident at an angle less than the critical angle (the minimum angle for total internal reflection). Instead, the two faces are coated to provide mirror surfaces. The two opposite transmitting faces are often coated with an antireflection coating to reduce spurious reflections. The fifth face of the prism is not used optically but truncates what would otherwise be an awkward angle joining the two mirrored faces. In cameras A variant of this prism is the roof pentaprism which is commonly used in the viewfinder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentamirror
A pentamirror is an optical device used in the viewfinder systems of various single-lens reflex cameras instead of the pentaprism. It is used to reverse again the laterally reversed image coming from the reflex mirror. Instead of the solid block of glass of the prism in pentaprism system, here 3 mirrors are used to perform the same task. This is cheaper and lighter, but generally produces a viewfinder image of lower quality and brightness. This optical device is often (more precisely) referred to as ''roof pentamirror'' because of the roof-like ridge.Paul R. Yoder. ''Opto-Mechanical Systems Design'', 2005page 435 See also *Pentaprism A pentaprism is a five-sided reflecting prism used to deviate a beam of light by a constant 90°, even if the entry beam is not at 90° to the prism. The beam reflects inside the prism ''twice'', allowing the transmission of an image through a r ... * Single-lens reflex camera Notes External linksUnderstanding Viewfinders [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Construction
Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and comes from Latin ''constructio'' (from ''com-'' "together" and ''struere'' "to pile up") and Old French ''construction''. To construct is the verb: the act of building, and the noun is construction: how something is built, the nature of its structure. In its most widely used context, construction covers the processes involved in delivering buildings, infrastructure, industrial facilities and associated activities through to the end of their life. It typically starts with planning, financing, and design, and continues until the asset is built and ready for use; construction also covers repairs and maintenance work, any works to expand, extend and improve the asset, and its eventual demolition, dismantling or decommissioning. The constructio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Right Angle
In geometry and trigonometry, a right angle is an angle of exactly 90 Degree (angle), degrees or radians corresponding to a quarter turn (geometry), turn. If a Line (mathematics)#Ray, ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin ''angulus rectus''; here ''rectus'' means "upright", referring to the vertical perpendicular to a horizontal base line. Closely related and important geometrical concepts are perpendicular lines, meaning lines that form right angles at their point of intersection, and orthogonality, which is the property of forming right angles, usually applied to Euclidean vector, vectors. The presence of a right angle in a triangle is the defining factor for right triangles, making the right angle basic to trigonometry. Etymology The meaning of ''right'' in ''right angle'' possibly refers to the Classical Latin, Latin adjective ''rectus'' 'erect, straight, upright, perp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plumb-bob
A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum. It is typically made of stone, wood, or lead, but can also be made of other metals. If it is used for decoration, it may be made of bone or ivory. The instrument has been used since at least the time of ancient EgyptDenys A. Stocks. Experiments in Egyptian archaeology: stoneworking technology in ncient Egypt'. Routledge; 2003. . p. 180. to ensure that constructions are "plumb", or vertical. It is also used in surveying, to establish the nadir with respect to gravity of a point in space. It is used with a variety of instruments (including levels, theodolites, and steel tapes) to set the instrument exactly over a fixed survey marker or to transcribe positions onto the ground for placing a marker. Etymology The ''plu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surveying
Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is called a land surveyor. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designed positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales. Surveyors work with elements of geodesy, geometry, trigonometry, regression analysis, physics, engineering, metrology, programming languages, and the law. They use equipment, such as total stations, robotic total stations, theodolites, GNSS receivers, retroreflectors, 3D scanners, LiDAR sensors, radios, inclinometer, handheld tablets, optical and digital levels, subsurface locators, d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medium Format (film)
Medium format has traditionally referred to a film format in photography and the related cameras and equipment that use film. Nowadays, the term applies to film and digital cameras that record images on media larger than the used in 35 mm photography (though not including 127 sizes), but smaller than (which is considered large format photography). In digital photography, medium format refers either to cameras adapted from medium-format film photography uses or to cameras making use of sensors larger than that of a 35 mm film frame. Some of the benefits of using medium-format digital cameras include higher resolution sensors, better low-light capabilities compared to a traditional 35mm DSLR, and a wider dynamic range. Characteristics Medium-format cameras made since the 1950s are generally less automated than smaller cameras made at the same time. For example, autofocus became available in consumer 35 mm cameras in 1977, but did not reach medium format until ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bronica
Bronica also Zenza Bronica (in Japanese: ) was a Japanese manufacturer of classic medium-format roll film cameras and photographic equipment based in Tokyo, Japan. Their single-lens reflex (SLR) system-cameras competed with Pentax, Hasselblad, Mamiya and others in the medium-format camera market. History Before introduction of the first of what would become a dynasty of Zenza Bronica cameras in 1959, the Latinized Zenza Bronica name was already a popular Japanese luxury goods brand of the Shinkodo Works (in Japanese: ) since 1947, specialized in the production of intricate crafted and decorated personal accessories, such as metal cigarette lighters and cases, cosmetic compacts, and watches, of diverse styles and designs. The company's founder Zenzaburō Yoshino (in Japanese: , b. 25 January 1911 — d. 23 November 1988), wherefrom the Latinized Zenza Bronica brand name is derived, was the third son born into a Japanese rice merchant family. At an early age Yoshino showed deep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Camera
A system camera or camera body is a camera with interchangeable components that constitutes the core of a system. Early representatives include Leica I Schraubgewinde (1930), Exakta (1936) and the Nikon F (1959). System cameras are often single-lens reflex (SLR) or twin-lens reflex (TLR) but can also be rangefinder cameras or, more recently, mirrorless interchangeable-lens cameras. Even point-and-shoot cameras usually include a tripod socket. A system camera includes at the very least a camera body and separate, interchangeable lenses, whence the alternative name interchangeable-lens camera (ILC). In addition it often includes: * Electronic flash units matching the camera's capabilities. * PC socket or tripod-adapter mounts for external flash units, rather than just a hot shoe * Mechanical, electric, or IR/ RF remote shutter release. * Extensive supplementary equipment for macro photography and photomicrography. * Adapters for third-party or legacy lenses, including tilt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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