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Wratten Number
Wratten numbers are a labeling system for optical filters, usually for photographic use comprising a number sometimes followed by a letter. The number denotes the color of the filter, but is arbitrary and does not encode any information (the 80A–80D are blue, the next filters in numerical order, 81A–81EF, are orange); letters almost always increase with increasing strength (the exception being 2B, 2A, 2C, 2E). They are named for the founder of the first photography company, British inventor Frederick Wratten. Wratten and partner C.E.K. Mees sold their company to Eastman Kodak in 1912, and Kodak started manufacturing Wratten filters. They remain in production, and are sold under license through the Tiffen corporation. Wratten filters are much used in observational astronomy by amateur astronomers. Color filters for visual observing made by GSO, Baader, Lumicon, or other companies are actually Wratten filters mounted in standard or 2 in (nominal, 48 mm actual) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kodak Wratten Filter 80A
The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorporated in New Jersey. Kodak provides packaging, functional printing, graphic communications, and professional services for businesses around the world. Its main business segments are Print Systems, Enterprise Inkjet Systems, Micro 3D Printing and Packaging, Software and Solutions, and Consumer and Film. It is best known for photographic film products. Kodak was founded by George Eastman and Henry A. Strong on May 23, 1892. During most of the 20th century, Kodak held a dominant position in photographic film. The company's ubiquity was such that its " Kodak moment" tagline entered the common lexicon to describe a personal event that deserved to be recorded for posterity. Kodak began to struggle financially in the late 1990s, as a result of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achromat
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. 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 equalled by the negative power of the flint lens element. Together they form a weak positive lens that will b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tungsten Lighting
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidation. Current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections. Incandescent bulbs are manufactured in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, and work equally well on either alternating current or direct current. As a result, the incandescent bulb became widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting. Incandescent bulbs are much less efficient than other types of electric lighting, converting less ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). The Kelvin scale is an absolute thermodynamic temperature scale, meaning it uses absolute zero as its null (zero) point. Historically, the Kelvin scale was developed by shifting the starting point of the much-older Celsius scale down from the melting point of water to absolute zero, and its increments still closely approximate the historic definition of a degree Celsius, but since 2019 the scale has been defined by fixing the Boltzmann constant to be exactly . Hence, one kelvin is equal to a change in the thermodynamic temperature that results in a change of thermal energy by . The temperature in degree Celsius is now defined as the temperature in kelvins minus 273.15, meaning t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Bars
SMPTE color bars are a television test pattern used where the NTSC video standard is utilized, including countries in North America. The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guideline (EG) 1-1990. Its components are a known standard, and created by test pattern generators. Comparing it as received to the known standard gives video engineers an indication of how an NTSC video signal has been altered by recording or transmission and what adjustments must be made to bring it back to specification. It is also used for setting a television monitor or receiver to reproduce NTSC chrominance and luminance information correctly. A precursor to the SMPTE test pattern was conceived by Norbert D. Larky (1927–2018) and David D. Holmes (1926–2006) of RCA Laboratories and first published in RCA Licensee Bulletin LB-819 on February 7, 1951. U.S. patent 2,742,525 Color Test Pattern Generator (now expired) was awarded on April 17, 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMPTE
The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and executives working in the media and entertainment industry. As an internationally recognized standards organization, SMPTE has published more than 800 technical standards and related documents for broadcast, filmmaking, digital cinema, audio recording, information technology (IT), and medical imaging. SMPTE also publishes the ''SMPTE Motion Imaging Journal'', provides networking opportunities for its members, produces academic conferences and exhibitions, and performs other industry-related functions. SMPTE membership is open to any individual or organization with an interest in the subject matter. In the US, SMPTE is a 501(c)(3) organization, 501(c)3 non-profit charitable organization. History The Motion Picture and Television Engineers was founded in 1913 by Cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Photography
''Top:'' tree photographed in the near infrared range. ''Bottom:'' same tree in the visible part of the spectrum. In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). ("Infrared filter" may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.) When these filters are used together with infrared-sensitive film or sensors, "in-camera effects" can be obtained; false-color or black-and-white images with a dreamlike or sometimes lurid appearance kn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionization, ionize atoms, it can cause chemical reactions and causes many substances to glow or fluorescence, fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wood's Glass
Wood's glass is an optical filter glass invented in 1903 by American physicist Robert Williams Wood (1868–1955), which allows ultraviolet and infrared light Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ... to pass through, while blocking most visible light. History Wood's glass was developed as a light filter used in communications during World War I. The glass filter worked both in infrared daylight communication and ultraviolet night communications by removing the visible components of a light beam, leaving only the "invisible radiation" as a signal beam. Wood's glass was commonly used to form the envelope for fluorescent and incandescent ultraviolet bulbs ("black lights"). In recent years, due to its disadvantages, other filter materials have largely replaced it."...a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Lenses
Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic or therapeutic reasons. In 2010, the worldwide market for contact lenses was estimated at $6.1 billion, while the US soft lens market was estimated at $2.1 billion.Nichols, Jason J., et a"ANNUAL REPORT: Contact Lenses 2010" January 2011. Multiple analysts estimated that the global market for contact lenses would reach $11.7 billion by 2015. , the average age of contact lens wearers globally was 31 years old, and two-thirds of wearers were female.Morgan, Philip B., et al"International Contact Lens Prescribing in 2010" ''Contact Lens Spectrum''. October 2011. People choose to wear contact lenses for many reasons. Aesthetics and cosmetics are main motivating factors for people who want to avoid wearing glasses or to change the appearance or c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "'' kerat-''" from the Greek word κέρας, ''horn''. Structure The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vessels with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
