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Low-dispersion Glass
Low-dispersion glass (LD glass) is a type of glass with reduced chromatic aberration, meaning the refractive index does not change as strongly with different wavelengths of light. In other words, the light passing through the glass has a smaller spread or dispersion between its constituent colors, resulting in a reduced "rainbow effect" at high-contrast edges. Wavelength dispersion in a certain material is characterized by its Abbe number; LD glass has a higher Abbe number than conventional types. Crown glass is an example of a relatively inexpensive low-dispersion glass. Branding Photographic lenses with LD glass have been branded and marketed with different names to indicate the use of low-dispersion elements in the optical design, including: * ''Anomalous Dispersion'' (AD): Minolta * ''Extra-low Dispersion'' or ''Extraordinary Dispersion'' (ED): Nikon, Olympus, Pentax * ''Extraordinary Low Dispersion'' (ELD): Sigma * ''Low Dispersion'' (LD): Tamron * ''Super Low Dispersion'' (S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kron Flint
KRON-TV (channel 4) is a television station licensed to San Francisco, California, United States, serving as the San Francisco Bay Area's outlet for The CW. Owned and operated by The CW's majority owner, Nexstar Media Group, KRON-TV has studios at the ABC Broadcast Center on Front Street in the city's historic Northeast Waterfront, immediately west of The Embarcadero north of the city's Financial District, in the same building as ABC owned-and-operated station KGO-TV, channel 7 (but with completely separate operations from that station). The transmitting antenna is located atop Sutro Tower in San Francisco. History NBC affiliation (1949–2001) In 1948, the Federal Communications Commission (FCC) authorized a construction permit by the Chronicle Publishing Company, publishers of the ''San Francisco Chronicle'' daily newspaper, for a new television station in San Francisco, KRON-TV. Chronicle Publishing was founded by brothers Charles and Michael de Young. The company already ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canon Inc
Canon Inc. (; Hepburn: ) is a Japanese multinational corporation headquartered in Ōta, Tokyo, specializing in optical, imaging, and industrial products, such as lenses, cameras, medical equipment, scanners, printers, and semiconductor manufacturing equipment. Canon has a primary listing on the Tokyo Stock Exchange and is a constituent of the TOPIX Core 30 and Nikkei 225 indexes. It used to have a secondary listing on the New York Stock Exchange. Name The company was originally named (). In 1934, it produced the ''Kwanon'', a prototype for Japan's first-ever 35mm camera with a focal-plane-based shutter. In 1947, the company name was changed to ''Canon Camera Co., Inc.'', shortened to ''Canon Inc.'' in 1969. The name Canon comes from Buddhist bodhisattva (), previously transliterated as Kuanyin, Kwannon, or Kwanon in English. History 1933–1970 The origins of Canon date back to the founding of Precision Optical Instruments Laboratory in Japan in 1933 by Takeshi Mitarai, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depth Of Field
The depth of field (DOF) is the distance between the nearest and the farthest objects that are in acceptably sharp focus (optics), focus in an image captured with a camera. See also the closely related depth of focus. Factors affecting depth of field For cameras that can only focus on one object distance at a time, depth of field is the distance between the nearest and the farthest objects that are in acceptably sharp focus in the image. "Acceptably sharp focus" is defined using a property called the "circle of confusion". The depth of field can be determined by focal length, distance to subject (object to be imaged), the acceptable circle of confusion size, and aperture. Limitations of depth of field can sometimes be overcome with various techniques and equipment. The approximate depth of field can be given by: \text \approx \frac for a given maximum acceptable circle of confusion , focal length , f-number , and distance to subject . As distance or the size of the acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wildlife Photography
Wildlife photography is a genre of photography concerned with documenting various forms of wildlife in their natural habitat. As well as requiring photography skills, wildlife photographers may need field craft skills. For example, some animals and birds are difficult to approach and thus a knowledge of the animal's and birds behavior is needed in order to be able to predict its actions. Photographing some species may require stalking skills or the use of a hide/blind for concealment. While wildlife photographs can be taken using basic equipment, successful photography of some types of wildlife requires specialist equipment, such as macro lenses for insects, long focal length lenses for birds and underwater cameras for marine life. History In the early days of photography, it was difficult to get a photograph of wildlife due to slow lenses and the low sensitivity of photographic media. Earlier photos of animals were often of captive ones. These included photos of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sports Photography
Sports photography refers to the genre of photography that covers all types of sports. In the majority of cases, professional sports photography is a branch of ''photojournalism,'' while amateur sports photography, such as photos of children playing association football, is a branch of ''vernacular photography.'' The main application of professional sports photography is for editorial purposes. Dedicated sports photographers usually work for newspapers, major wire agencies or sports magazines. However, sports photography is also used for advertising purposes both to build a brand and to promote a sport in a way that cannot be accomplished by editorial means. Equipment Equipment typically used for sports photography includes a Digital single-lens reflex camera, digital single-lens reflex (DSLR) camera or Mirrorless interchangeable-lens camera, Mirrorless Camera with high Burst mode (photography), continuous shooting speeds and interchangeable lenses ranging from 14mm to 400m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shutter Speed
In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph. The amount of light that reaches the Photographic film, film or image sensor is proportional to the exposure time. of a second will let half as much light in as . Introduction The camera's shutter speed, the lens's aperture or f-stop, and the scene's luminance together determine the amount of light that reaches the film or sensor (the exposure (photography), exposure). Exposure value (EV) is a quantity that accounts for the shutter speed and the f-number. Once the sensitivity to light of the recording surface (either film or sensor) is set in numbers expressed in "Film speed#ISO, ISOs" (e.g. 200 ISO, 400 ISO), the light emitted by the scene photographed can be controlled through aperture and shutter-speed to match the film or sensor sensitivit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F-number
An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Professional, p. 183. The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and Exposure (photography), exposure of a photograph. The f-number is dimensionless number, dimensionless and is usually expressed using a lower-case Ƒ, hooked f with the format ''N'', where ''N'' is the f-number. The f-number is also known as the inverse relative aperture, because it is the Multiplicative inverse, inverse of the relative aperture, defined as the aperture diameter divided by focal length. The relative aperture indicates how much light can pass through the lens at a given focal length. A lower f-number means a larger relative apertur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aspheric Lens
An aspheric lens or asphere (often labeled ''ASPH'' on eye pieces) is a lens whose surface profiles are not portions of a sphere or cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens. The asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations such as astigmatism, compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and sometimes cheaper than the multi-lens design. Aspheric elements are used in the design of multi-element wide-angle and fast normal lenses to reduce aberrations. They are also used in combination with reflective elements (catadioptric systems) such as the aspherical Schmidt corrector plate used in the Schmidt cameras and the Schmidt–Cassegrain telescopes. Small molded aspheres are often used for collimating diode lasers. Aspher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spherical Aberration
In optics, spherical aberration (SA) is a type of aberration found in optical systems that have elements with spherical surfaces. This phenomenon commonly affects lenses and curved mirrors, as these components are often shaped in a spherical manner for ease of manufacturing. Light rays that strike a spherical surface off-centre are refracted or reflected more or less than those that strike close to the centre. This deviation reduces the quality of images produced by optical systems. The effect of spherical aberration was first identified in the 11th century by Ibn al-Haytham who discussed it in his work Kitāb al-Manāẓir. Overview A spherical lens has an aplanatic point (i.e., no spherical aberration) only at a lateral distance from the optical axis that equals the radius of the spherical surface divided by the index of refraction of the lens material. Spherical aberration makes the focus of telescopes and other instruments less than ideal. This is an important effect, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focal Length
The focal length of an Optics, optical system is a measure of how strongly the system converges or diverges light; it is the Multiplicative inverse, inverse of the system's optical power. A positive focal length indicates that a system Convergence (optics), converges light, while a negative focal length indicates that the system Divergence (optics), diverges light. A system with a shorter focal length bends the Ray (optics), rays more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a thin lens in air, a positive focal length is the distance over which initially Collimated beam, collimated (parallel) rays are brought to a Focus (optics), focus, or alternatively a negative focal length indicates how far in front of the lens a point source must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system's optical power. In mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephoto Lens
A telephoto lens, also known as telelens, is a specific type of a long-focus lens used in photography and cinematography, in which the physical length of the lens is shorter than the focal length. This is achieved by incorporating a special lens 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. Construction A simple photographic lens may be constructed using one lens element of a given focal length; to focus on an object at infinity, the distance from this single lens to focal plane of the camera (where the sensor or film is) has to be adjusted to the focal length of that lens. For example, g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achromatic Doublet
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane. Wavelengths in between these two then have better focus error than could be obtained with a simple lens. The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion. Typically, one element is a negative (concave) element made out of flint glass such as F2, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass such as BK7, which has lower dispersion. The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other. In the most common type (shown), the positive power of the crown lens element is not quite e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
