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Cokin
Cokin is a French manufacturer of optical filters for photography. The system allows filters such as rectangular graduated neutral density filters which are versatile in use. History Cokin are particularly noted for their "Creative Filter System". It was invented by photographer Jean Coquin and introduced in 1978. Based primarily around square filters, these require a holder which is attached to the lens via a simple adapter ring of the appropriate size. Unlike screw-thread circular filters, which are each tied to lenses of a specific diameter, those in the system can be used with any lens, provided they are large enough to cover it sufficiently. (Only the adapter ring may need changing). Production The system includes a wide range of filters including color correction, plain and coloured graduated filters, diffraction, diffusion and polarizers. The material is a polymer, CR-39 sometimes advertised as "organic glass". Cokin produce various differently-sized versions of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cokin
Cokin is a French manufacturer of optical filters for photography. The system allows filters such as rectangular graduated neutral density filters which are versatile in use. History Cokin are particularly noted for their "Creative Filter System". It was invented by photographer Jean Coquin and introduced in 1978. Based primarily around square filters, these require a holder which is attached to the lens via a simple adapter ring of the appropriate size. Unlike screw-thread circular filters, which are each tied to lenses of a specific diameter, those in the system can be used with any lens, provided they are large enough to cover it sufficiently. (Only the adapter ring may need changing). Production The system includes a wide range of filters including color correction, plain and coloured graduated filters, diffraction, diffusion and polarizers. The material is a polymer, CR-39 sometimes advertised as "organic glass". Cokin produce various differently-sized versions of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cokin Filters (Stacked Cases)
Cokin is a French manufacturer of optical filters for photography. The system allows filters such as rectangular graduated neutral density filters which are versatile in use. History Cokin are particularly noted for their "Creative Filter System". It was invented by photographer Jean Coquin and introduced in 1978. Based primarily around square filters, these require a holder which is attached to the lens via a simple adapter ring of the appropriate size. Unlike screw-thread circular filters, which are each tied to lenses of a specific diameter, those in the system can be used with any lens, provided they are large enough to cover it sufficiently. (Only the adapter ring may need changing). Production The system includes a wide range of filters including color correction, plain and coloured graduated filters, diffraction, diffusion and polarizers. The material is a polymer, CR-39 sometimes advertised as "organic glass". Cokin produce various differently-sized versions of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photographic Filter
In photography and cinematography, a filter is a camera accessory consisting of an optical filter that can be inserted into the optical path. The filter can be of a square or oblong shape and mounted in a holder accessory, or, more commonly, a glass or plastic disk in a metal or plastic ring frame, which can be screwed into the front of or clipped onto the camera lens. Filters modify the images recorded. Sometimes they are used to make only subtle changes to images; other times the image would simply not be possible without them. In monochrome photography, coloured filters affect the relative brightness of different colours; red lipstick may be rendered as anything from almost white to almost black with different filters. Others change the colour balance of images, so that photographs under incandescent lighting show colours as they are perceived, rather than with a reddish tinge. There are filters that distort the image in a desired way, diffusing an otherwise sharp image, adding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graduated Neutral Density Filter
A graduated neutral-density filter, also known as a graduated ND filter, split neutral-density filter, or just a graduated filter, is an optical filter that has a variable light transmission. Typically half of the filter is of neutral density which transitions, either abruptly or gradually, into the other half which is clear. It is used to bring an overly-bright part of a scene into the dynamic range of film or sensor. For example, it can be used to darken a bright sky so that both the sky and subject can be properly exposed. ND filters can come in a variety of shapes and sizes and densities and can be used in all types of photographic applications from still photography, motion photography and scientific applications. Center-spot filters are ND graduated filters that are slightly opaque in the center and are clear at edges. These are used for special effects or to compensate for light falloff that is natural with large optics. History Graduated filters were used in the early t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graduated Neutral Density Filter
A graduated neutral-density filter, also known as a graduated ND filter, split neutral-density filter, or just a graduated filter, is an optical filter that has a variable light transmission. Typically half of the filter is of neutral density which transitions, either abruptly or gradually, into the other half which is clear. It is used to bring an overly-bright part of a scene into the dynamic range of film or sensor. For example, it can be used to darken a bright sky so that both the sky and subject can be properly exposed. ND filters can come in a variety of shapes and sizes and densities and can be used in all types of photographic applications from still photography, motion photography and scientific applications. Center-spot filters are ND graduated filters that are slightly opaque in the center and are clear at edges. These are used for special effects or to compensate for light falloff that is natural with large optics. History Graduated filters were used in the early t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Filter
An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which are either dyed in the bulk or have interference coatings. The optical properties of filters are completely described by their frequency response, which specifies how the magnitude and phase of each frequency component of an incoming signal is modified by the filter. Filters mostly belong to one of two categories. The simplest, physically, is the absorptive filter; then there are interference or dichroic filters. Many optical filters are used for optical imaging and are manufactured to be transparent; some used for light sources can be translucent. Optical filters selectively transmit light in a particular range of wavelengths, that is, colours, while absorbing the remainder. They can usually pass long wavelengths only (longpass), short wavelengths only (shortpass), or a band of wavelengths, blocking both lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed in many fields of science, manufacturing (e.g., photolithography), and business, as well as its more direct uses for art, film and video production, recreational purposes, hobby, and mass communication. 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 image sensor, this produces an electrical charge at each pixel, which is electronically processed and stored in a digital image file for subsequent display or processing. The result with photographic emulsion is an invisible latent image, which is later chemically "developed" into a visible image, either negative or positive, depending on the purp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CR-39
Poly(allyl diglycol carbonate) (PADC) is a plastic commonly used in the manufacture of eyeglass lenses alongside the material PMMA (polymethyl methacrylate). The monomer is allyl diglycol carbonate (ADC). The term CR-39 technically refers to the ADC monomer, but is more commonly used to refer to the finished plastic. The abbreviation stands for "Columbia Resin #39", which was the 39th formula of a thermosetting plastic developed by the Columbia Resins project in 1940. The first commercial use of CR-39 monomer (ADC) was to help create glass-reinforced plastic fuel tanks for the B-17 bomber aircraft in World War II, reducing the weight and increasing the range of the bomber. After the war, the Armorlite Lens Company in California is credited with manufacturing the first CR-39 eyeglass lenses in 1947. CR-39 plastic has an index of refraction of 1.498 and an Abbe number of 58. CR-39 is now a trade-marked product of PPG Industries. An alternative use includes a purified version ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
De Facto
''De facto'' ( ; , "in fact") describes practices that exist in reality, whether or not they are officially recognized by laws or other formal norms. It is commonly used to refer to what happens in practice, in contrast with ''de jure'' ("by law"), which refers to things that happen according to official law, regardless of whether the practice exists in reality. History In jurisprudence, it mainly means "practiced, but not necessarily defined by law" or "practiced or is valid, but not officially established". Basically, this expression is opposed to the concept of "de jure" (which means "as defined by law") when it comes to law, management or technology (such as standards) in the case of creation, development or application of "without" or "against" instructions, but in accordance with "with practice". When legal situations are discussed, "de jure" means "expressed by law", while "de facto" means action or what is practiced. Similar expressions: "essentially", "unofficial", "in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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