1.
Color scheme
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In color theory, a color scheme is the choice of colors used in design for a range of media. For example, the Achromatic use of a background with black text is an example of a basic. Color schemes are used to style and appeal. Colors that create a feeling when used together will commonly accompany each other in color schemes. A basic color scheme will use two colors that look appealing together, the addition of light blue creates an Accented Analogous color scheme. Color schemes can contain different Monochromatic shades of a color, for example. A color scheme in marketing is referred to as a dress and can be sometimes be copyrighted. Color schemes are described in terms of logical combinations of colors on a color wheel. Different types of schemes are used, Monochromatic colors are all the colors of a single hue. Monochromatic color schemes are derived from a single hue, and extended using its shades, tones and tints (that is. As a result, the energy is more subtle and peaceful due to a lack of contrast of hue. For the mixing of colored light, Newtons color wheel is used to describe complementary colors. Newton offered as a conjecture that colors exactly opposite one another on the hue circle cancel out each others hue, this concept was demonstrated more thoroughly in the 19th century. A key assumption in Newtons hue circle was that the fiery or maximum saturated hues are located on the circumference of the circle, while achromatic white is at the center. The split-complementary color scheme is a variation of the color scheme. In addition to the color, it uses the two Analogous colors adjacent to its complement. Split-complementary color scheme has the strong visual contrast as the complementary color scheme. Any color that lacks strong chromatic content is said to beunsaturated, achromatic, pure achromatic colors include black, white and all grays, near neutrals include browns, tans, pastels and darker colors
2.
User interface
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The user interface, in the industrial design field of human–computer interaction, is the space where interactions between humans and machines occur. Examples of this concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology. Generally, the goal of user interface design is to produce a user interface makes it easy, efficient. This generally means that the needs to provide minimal input to achieve the desired output. Other terms for user interface are man–machine interface and when the machine in question is a computer human–computer interface, the user interface or human–machine interface is the part of the machine that handles the human–machine interaction. Membrane switches, rubber keypads and touchscreens are examples of the part of the Human Machine Interface which we can see. In complex systems, the interface is typically computerized. The term human–computer interface refers to this kind of system, in the context of computing the term typically extends as well to the software dedicated to control the physical elements used for human-computer interaction. The engineering of the interfaces is enhanced by considering ergonomics. The corresponding disciplines are human factors engineering and usability engineering, which is part of systems engineering, tools used for incorporating human factors in the interface design are developed based on knowledge of computer science, such as computer graphics, operating systems, programming languages. Nowadays, we use the graphical user interface for human–machine interface on computers. There is a difference between a user interface and an interface or a human–machine interface. A human-machine interface is typically local to one machine or piece of equipment, an operator interface is the interface method by which multiple equipment that are linked by a host control system is accessed or controlled. The system may expose several user interfaces to serve different kinds of users, for example, a computerized library database might provide two user interfaces, one for library patrons and the other for library personnel. The user interface of a system, a vehicle or an industrial installation is sometimes referred to as the human–machine interface. HMI is a modification of the original term MMI, in practice, the abbreviation MMI is still frequently used although some may claim that MMI stands for something different now. Another abbreviation is HCI, but is commonly used for human–computer interaction
3.
Cathode ray tube
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The cathode ray tube is a vacuum tube that contains one or more electron guns and a phosphorescent screen, and is used to display images. It modulates, accelerates, and deflects electron beam onto the screen to create the images, the images may represent electrical waveforms, pictures, radar targets, or others. CRTs have also used as memory devices, in which case the visible light emitted from the fluorescent material is not intended to have significant meaning to a visual observer. In television sets and computer monitors, the front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three beams, one for each additive primary color with a video signal as a reference. A CRT is constructed from an envelope which is large, deep, fairly heavy. The interior of a CRT is evacuated to approximately 0.01 Pa to 133 nPa. evacuation being necessary to facilitate the flight of electrons from the gun to the tubes face. That it is evacuated makes handling an intact CRT potentially dangerous due to the risk of breaking the tube and causing a violent implosion that can hurl shards of glass at great velocity. As a matter of safety, the face is made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions. Flat panel displays can also be made in large sizes, whereas 38 to 40 was about the largest size of a CRT television, flat panels are available in 60. Cathode rays were discovered by Johann Hittorf in 1869 in primitive Crookes tubes and he observed that some unknown rays were emitted from the cathode which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, the earliest version of the CRT was known as the Braun tube, invented by the German physicist Ferdinand Braun in 1897. It was a diode, a modification of the Crookes tube with a phosphor-coated screen. In 1907, Russian scientist Boris Rosing used a CRT in the end of an experimental video signal to form a picture. He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television. The first cathode ray tube to use a hot cathode was developed by John B. Johnson and Harry Weiner Weinhart of Western Electric and it was named by inventor Vladimir K. Zworykin in 1929. RCA was granted a trademark for the term in 1932, it released the term to the public domain in 1950. The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, in oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television and other large CRTs
4.
Phosphor
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A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness, and fluorescent materials, where the emission decay takes place over tens of nanoseconds, Phosphors are often transition metal compounds or rare earth compounds of various types. The most common uses of phosphors are in CRT displays and fluorescent lights, CRT phosphors were standardized beginning around World War II and designated by the letter P followed by a number. Phosphorus, the element named for its light-emitting behavior, emits light due to chemiluminescence. A material can emit light either through incandescence, where all atoms radiate, or by luminescence, in inorganic phosphors, these inhomogeneities in the crystal structure are created usually by addition of a trace amount of dopants, impurities called activators. The wavelength emitted by the center is dependent on the atom itself. The scintillation process in inorganic materials is due to the band structure found in the crystals. An incoming particle can excite an electron from the band to either the conduction band or the exciton band. This leaves a hole behind, in the valence band. Impurities create electronic levels in the forbidden gap, the excitons are loosely bound electron-hole pairs that wander through the crystal lattice until they are captured as a whole by impurity centers. The latter then rapidly de-excite by emitting scintillation light, in case of inorganic scintillators, the activator impurities are typically chosen so that the emitted light is in the visible range or near-UV where photomultipliers are effective. The holes associated with electrons in the band are independent from the latter. Those holes and electrons are captured successively by impurity centers exciting certain metastable states not accessible to the excitons, the delayed de-excitation of those metastable impurity states, slowed down by reliance on the low-probability forbidden mechanism, again results in light emission. Many phosphors tend to lose efficiency gradually by several mechanisms, the degradation of electroluminescent devices depends on frequency of driving current, the luminance level, and temperature, moisture impairs phosphor lifetime very noticeably as well. Harder, high-melting, water-insoluble materials display lower tendency to lose luminescence under operation, examples, BaMgAl10O17, Eu2+, a plasma display phosphor, undergoes oxidation of the dopant during baking. Thin coating of aluminium phosphate or lanthanum phosphate is effective in creation a barrier layer blocking access of oxygen to the BAM phosphor, for the cost of reduction of phosphor efficiency. Addition of hydrogen, acting as an agent, to argon in the plasma displays significantly extends the lifetime of BAM, Eu2+ phosphor. Y2O3, Eu phosphors under electron bombardment in presence of oxygen form a non-phosphorescent layer on the surface, the traps also damage the crystal lattice
5.
Cathode ray
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Cathode rays are streams of electrons observed in vacuum tubes. They were first observed in 1869 by German physicist Johann Hittorf, electrons were discovered as the constituents of cathode rays. In 1897 British physicist J. J. Thomson showed the rays were composed of a previously unknown negatively charged particle, Cathode ray tubes use a focused beam of electrons deflected by electric or magnetic fields to create the image in a classic television set. Cathode rays are made up of charged particles. Cathode rays are so named because they are emitted by the electrode, or cathode. This contrasts with cations, which are charged and go — Greek ἰόν — toward a cathode in solution. To release electrons into the tube, they first must be detached from the atoms of the cathode, modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it. The increased random heat motion of the filament knocks electrons out at the surface of the filament, since the electrons have a negative charge, they are repelled by the cathode and attracted to the anode. They travel in straight lines through the empty tube, the voltage applied between the electrodes accelerates these low mass particles to high velocities. Researchers noticed that objects placed in the tube in front of the cathode could cast a shadow on the glowing wall, and realized that something must be travelling in straight lines from the cathode. After the electrons reach the anode, they travel through the wire to the power supply and back to the cathode. The current in a beam of cathode rays through a tube can be controlled by passing it through a screen of wires to which a small voltage is applied. The electric field of the wires deflects some of the electrons, thus a small voltage on the grid can be made to control a much larger voltage on the anode. This is the used in vacuum tubes to amplify electrical signals. These are used in cathode ray tubes, found in televisions and computer monitors, after the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a distance through low pressure air than through atmospheric pressure air. In 1838, Michael Faraday passed a current through an air filled glass tube and noticed a strange light arc with its beginning at the cathode. In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with a pump, to a pressure of around 10−3 atm and found that, instead of an arc
6.
Monochrome
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Monochrome describes paintings, drawings, design, or photographs in one color or values of one color. A monochromatic object or image reflects colors in shades of limited colors or hues, images using only shades of grey are called grayscale or black-and-white. However, scientifically speaking, monochromatic light refers to light of a narrow band of wavelengths. In computing, monochrome has two meanings, it may mean having only one color which is either on or off, a monochrome computer display is able to display only a single color, often green, amber, red or white, and often also shades of that color. In film photography, monochrome is typically the use of black-and-white film, originally, all photography was done in monochrome. Although color photography was possible even in the late 19th century, easily used color films, if the red channel is eliminated and the green and blue combined then the effect will be similar to that of orthochromatic film or the use of a cyan filter on panchromatic film. The selection of weighting thus allows a range of artistic expression in the final monochromatic image. For production of an image the original color stereogram source may first be reduced to monochrome in order to simplify the rendering of the image. This is sometimes required in cases where an image would render in a confusing manner given the colors and patterns present in the source image. In physics, monochromatic light is electromagnetic radiation of a single frequency, even very controlled sources such as lasers operate in a range of frequencies. In practice, filtered light, diffraction grating separated light and laser light are all referred to as monochromatic. Often light sources can be compared and one be labeled as “more monochromatic”
7.
RGB color model
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The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three primary colors, red, green and blue. Before the electronic age, the RGB color model already had a theory behind it. Thus an RGB value does not define the same color across devices without some kind of color management, typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of technologies, computer and mobile phone displays, video projectors, multicolor LED displays. Color printers, on the hand are not RGB devices. This article discusses concepts common to all the different color spaces that use the RGB color model, to form a color with RGB, three light beams must be superimposed. Each of the three beams is called a component of color, and each of them can have an arbitrary intensity, from fully off to fully on. The RGB color model is additive in the sense that the three beams are added together, and their light spectra add, wavelength for wavelength. This is essentially opposite to the color model that applies to paints, inks, dyes. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, a secondary color is formed by the sum of two primary colors of equal intensity, cyan is green+blue, magenta is red+blue, and yellow is red+green. The RGB color model itself does not define what is meant by red, green and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green and blue primaries are defined, the normal three kinds of light-sensitive photoreceptor cells in the human eye respond most to yellow, green, and violet light. As an example, suppose that light in the range of wavelengths enters the eye. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more, the difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously. The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, to reproduce the color photograph, three matching projections over a screen in a dark room were necessary
8.
Teletext
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Teletext is a television information retrieval service created in the United Kingdom in the early 1970s by the Philips Lead Designer for VDUs, John Adams. It offers a range of text-based information, typically including news, weather, paged subtitle information is also transmitted within the television signal. It is closely linked to the PAL broadcast system used in Europe, other teletext systems have been developed to work with the SECAM and NTSC systems, but teletext failed to gain widespread acceptance in North America and other areas where NTSC is used. In contrast, teletext is nearly ubiquitous across Europe as well as other regions. Common teletext services include TV schedules, regularly updated current affairs and sport news, Teletext is broadcast in numbered pages. For example, a list of news headlines appear on page 110. The broadcaster constantly sends out pages in sequence, there will typically be a delay of a few seconds from requesting the page and it being broadcast and displayed, the time being entirely dependent in the number of pages being broadcast. More sophisticated receivers use a memory to store some or all of the teletext pages as they are broadcast. For this reason, some pages are broadcast more than once in each cycle, Teletext is also used for carrying special packets interpreted by TVs and video recorders, containing information about channels, programming, etc. Transmitting and displaying subtitles was relatively easy and it requires limited bandwidth, at a rate of perhaps a few words per second. However, it was found that by combining even a slow data rate with a memory, whole pages of information could be sent. In the early 1970s work was in progress in Britain to develop such a system, the goal was to provide UK rural homes with electronic hardware that could download pages of up-to-date news, reports, facts and figures targeting U. K. agriculture. The original idea was the brainchild of Philips Laboratories in 1970, in 1971, CAL engineer John Adams created a design and proposal for UK broadcasters. A major objective for Adams during the development stage was to make Teletext affordable to the home user. In reality, there was no scope to make an economic Teletext system with 1971 technology, however, as low cost was essential to the projects long term success, this obstacle had to be overcome. Meanwhile, the General Post Office, whose telecommunications division later became British Telecom, had been researching a similar concept since the late 1960s, unlike Teledata which was a one-way service carried in the existing TV signal, Viewdata was a two-way system using telephones. Since the Post Office owned the telephones, this was considered to be an excellent way to more customers to use the phones. In 1972 the BBC demonstrated their system, now known as Ceefax, the Independent Television Authority announced their own service in 1973, known as ORACLE
9.
WYSIWYG
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WYSIWYG is an acronym for what you see is what you get. WYSIWYG implies a user interface allows the user to view something very similar to the end result while the document is being created. In general, WYSIWYG implies the ability to manipulate the layout of a document without having to type or remember names of layout commands. The actual meaning depends on the perspective, e. g. WYSIWYG also describes ways to manipulate 3D models in stereo-chemistry, computer-aided design. Modern software does a job of optimizing the screen display for a particular type of output. For example, a processor is optimized for output to a typical printer. The software often emulates the resolution of the printer in order to get as close as possible to WYSIWYG, however, that is not the main attraction of WYSIWYG, which is the ability of the user to be able to visualize what they are producing. In many situations, the differences between what the user sees and what the user gets are unimportant. A preview mode, in which the attempts to present a representation that is as close to the final result as possible. Before the adoption of WYSIWYG techniques, text appeared in editors using the standard typeface. Users were required to enter special non-printing control codes to indicate that text should be in boldface, italics. In this environment there was little distinction between text editors and word processors. These applications typically used an arbitrary markup language to define the codes/tags, each program had its own special way to format a document, and it was a difficult and time-consuming process to change from one word processor to another. The use of tags and codes remains popular today in some applications due to their ability to store complex formatting information. When the tags are made visible in the editor, however, they occupy space in the text and so disrupt the desired layout. The Alto monitor was designed so that one page of text could be seen and then printed on the first laser printers. Bravo was released commercially and the software included in the Xerox Star can be seen as a direct descendant of it. The first release, named BRUNO, ran on the HP1000 minicomputer taking advantage of HPs first bitmapped computer terminal the HP2640, BRUNO was then ported to the HP-3000 and re-released as HP Draw
10.
Word processor
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A word processor is an electronic device or computer software application, that performs the task of composing, editing, formatting, and printing of documents. Later models introduced innovations such as spell-checking programs, and improved formatting options, as of 2009 there were only two U. S. companies, Classic and AlphaSmart, which still made them. Many older machines, however, remain in use, since 2009, Sentinel has offered a machine described as a word processor, but it is more accurately a highly specialised microcomputer used for accounting and publishing. Most are powerful systems consisting of one or more programs that can produce a combination of images, graphics and text, the latter handled with type-setting capability. In its simplest form, a processor is like an Expensive Typewriter or Typewriter machine, with the improvement of being able to proofread. Microsoft Word is the most widely used word processing software according to a tracking system built into the software. Microsoft estimates that half a billion people use the Microsoft Office suite. Many other word processing applications exist, including WordPerfect and open source applications OpenOffice. org Writer, LibreOffice Writer, AbiWord, KWord, web-based word processors, such as Office Online or Google Docs are a relatively new category. Word processors evolved dramatically once they became software programs rather than dedicated machines and they can usefully be distinguished from text editors, the category of software they evolved from. A text editor is a program that is used for typing, copying, pasting, text editors do not format lines or pages. Text editors are now used mainly by programmers, website designers, computer system administrators and they are also useful when fast startup times, small file sizes, editing speed, and simplicity of operation are valued, and when formatting is unimportant. Due to their use in managing complex software projects, text editors can sometimes provide better facilities for managing large writing projects than a word processor. Word processing added to the editor the ability to control type style and size, to manage lines, to format documents into pages. Functions now taken for granted were added incrementally, sometimes by purchase of independent providers of add-on programs, spell checking, grammar checking and mail merge were some of the most popular add-ons for early word processors. Word processors are capable of hyphenation, and the management. More advanced features found in recent word processors include, Collaborative editing, allowing users to work on the same document. Management, editing, and positioning of visual material, and sometimes sound files, automatically managed cross-references to pages or notes. Version control of a document, permitting reconstruction of its evolution, styles, which automate consistent formatting of text body, titles, subtitles, highlighted text, and so on
11.
OLED
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An organic light-emitting diode is a light-emitting diode in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes, typically, at least one of these electrodes is transparent, OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld game consoles and PDAs. A major area of research is the development of white OLED devices for use in lighting applications. There are two families of OLED, those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates an electrochemical cell which has a slightly different mode of operation. OLED displays can use either passive-matrix or active-matrix addressing schemes, an OLED display works without a backlight, thus, it can display deep black levels and can be thinner and lighter than a liquid crystal display. In low ambient light conditions, an OLED screen can achieve a higher contrast ratio than an LCD, andré Bernanose and co-workers at the Nancy-Université in France made the first observations of electroluminescence in organic materials in the early 1950s. They applied high alternating voltages in air to such as acridine orange. The proposed mechanism was either direct excitation of the dye molecules or excitation of electrons, in 1960 Martin Pope and some of his co-workers at New York University developed ohmic dark-injecting electrode contacts to organic crystals. They further described the energetic requirements for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern OLED devices, the proposed mechanism was field-accelerated electron excitation of molecular fluorescence. Also in 1965, W. Helfrich and W. G and their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules. Roger Partridge made the first observation of electroluminescence from polymer films at the National Physical Laboratory in the United Kingdom, the device consisted of a film of poly up to 2.2 micrometers thick located between two charge injecting electrodes. The results of the project were patented in 1975 and published in 1983, hong Kong-born American physical chemist Ching W. Tang and his co-worker Steven Van Slyke at Eastman Kodak built the first practical OLED device in 1987. This was a revolution for the technology, Universal Display Corporation holds the majority of patents concerning the commercialization of OLEDs. A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a substrate, the organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over part or all of the molecule. These materials have conductivity ranging from insulators to conductors, and are therefore considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals of organic semiconductors are analogous to the valence, originally, the most basic polymer OLEDs consisted of a single organic layer
12.
Liquid-crystal display
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A liquid-crystal display is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome and they use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements. LCDs are used in a range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays. Small LCD screens are common in consumer devices such as digital cameras, watches, calculators. LCD screens are used on consumer electronics products such as DVD players, video game devices. LCD screens have replaced heavy, bulky cathode ray tube displays in all applications. LCD screens are available in a range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to huge. Since LCD screens do not use phosphors, they do not suffer image burn-in when an image is displayed on a screen for a long time. LCDs are, however, susceptible to image persistence, the LCD screen is more energy-efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery-powered electronic equipment more efficiently than CRTs can be, by 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes. Without the liquid crystal between the filters, light passing through the first filter would be blocked by the second polarizer. Before an electric field is applied, the orientation of the molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic device, the surface alignment directions at the two electrodes are perpendicular to other, and so the molecules arrange themselves in a helical structure. This induces the rotation of the polarization of the incident light, and this light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, color LCD systems use the same technique, with color filters used to generate red, green, and blue pixels. The optical effect of a TN device in the state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage. When no image is displayed, different arrangements are used, for this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers
13.
World Wide Web
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The World Wide Web is an information space where documents and other web resources are identified by Uniform Resource Locators, interlinked by hypertext links, and can be accessed via the Internet. English scientist Tim Berners-Lee invented the World Wide Web in 1989 and he wrote the first web browser computer program in 1990 while employed at CERN in Switzerland. The Web browser was released outside of CERN in 1991, first to research institutions starting in January 1991. The World Wide Web has been central to the development of the Information Age and is the primary tool billions of people use to interact on the Internet, Web pages are primarily text documents formatted and annotated with Hypertext Markup Language. In addition to formatted text, web pages may contain images, video, audio, embedded hyperlinks permit users to navigate between web pages. Multiple web pages with a theme, a common domain name. Website content can largely be provided by the publisher, or interactive where users contribute content or the content depends upon the user or their actions, websites may be mostly informative, primarily for entertainment, or largely for commercial, governmental, or non-governmental organisational purposes. In the 2006 Great British Design Quest organised by the BBC and the Design Museum, Tim Berners-Lees vision of a global hyperlinked information system became a possibility by the second half of the 1980s. By 1985, the global Internet began to proliferate in Europe, in 1988 the first direct IP connection between Europe and North America was made and Berners-Lee began to openly discuss the possibility of a web-like system at CERN. Such a system, he explained, could be referred to using one of the meanings of the word hypertext. At this point HTML and HTTP had already been in development for two months and the first Web server was about a month from completing its first successful test. While the read-only goal was met, accessible authorship of web content took longer to mature, with the concept, WebDAV, blogs, Web 2.0. The proposal was modelled after the SGML reader Dynatext by Electronic Book Technology, a NeXT Computer was used by Berners-Lee as the worlds first web server and also to write the first web browser, WorldWideWeb, in 1990. By Christmas 1990, Berners-Lee had built all the necessary for a working Web, the first web browser. The first web site, which described the project itself, was published on 20 December 1990, jones stored it on a magneto-optical drive and on his NeXT computer. On 6 August 1991, Berners-Lee published a summary of the World Wide Web project on the newsgroup alt. hypertext. This date is confused with the public availability of the first web servers. The first server outside Europe was installed at the Stanford Linear Accelerator Center in Palo Alto, California, accounts differ substantially as to the date of this event
14.
GIF
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The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It also supports animations and allows a separate palette of up to 256 colors for each frame, GIF images are compressed using the Lempel–Ziv–Welch lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985, controversy over the licensing agreement between the software patent holder, Unisys, and CompuServe in 1994 spurred the development of the Portable Network Graphics standard. By 2004 all the relevant patents had expired, CompuServe introduced the GIF format in 1987 to provide a color image format for their file downloading areas, replacing their earlier run-length encoding format, which was black and white only. The original version of the GIF format was called 87a, in 1989, CompuServe released an enhanced version, called 89a, which added support for animation delays, transparent background colors, and storage of application-specific metadata. The 89a specification also supports incorporating text labels as text, but as there is control over display fonts. The two versions can be distinguished by looking at the first six bytes of the file, which, CompuServe encouraged the adoption of GIF by providing downloadable conversion utilities for many computers. By December 1987, for example, an Apple IIGS user could view pictures created on an Atari ST or Commodore 64, GIF was one of the first two image formats commonly used on Web sites, the other being the black-and-white XBM. In September 1995 Netscape Navigator 2.0 added Animated GIF support, the feature of storing multiple images in one file, accompanied by control data, is used extensively on the Web to produce simple animations. As a noun, the word GIF is found in the editions of many dictionaries. In 2012, the American wing of the Oxford University Press recognized GIF as a verb as well, meaning to create a GIF file, as in GIFing was perfect medium for sharing scenes from the Summer Olympics. The presss lexicographers voted it their word of the year, saying that GIFs have evolved into a tool with serious applications including research, in May 2015 Facebook added GIF support, even though they originally didnt support them on their site. The creators of the format pronounced the word as jif with a soft G /ˈdʒɪf/ as in gin, the word is now also widely pronounced with a hard G /ˈɡɪf/ as in gift. The American Heritage Dictionary cites both, indicating jif as the pronunciation, while Cambridge Dictionary of American English offers only the hard-G pronunciation. Merriam-Websters Collegiate Dictionary and the OED cite both pronunciations, but place gif in the default position, the New Oxford American Dictionary gave only jif in its 2nd edition but updated it to jif, gif in its 3rd edition. The disagreement over the pronunciation led to heated Internet debate, the White House and TV program Jeopardy. Also waded into the debate during 2013, GIFs are suitable for sharp-edged line art with a limited number of colors. This takes advantage of the formats lossless compression, which favors flat areas of color with well defined edges
15.
Portable Network Graphics
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Portable Network Graphics is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format, PNG supports palette-based images, grayscale images, and full-color non-palette-based RGB/RGBA images. PNG was designed for transferring images on the Internet, not for professional-quality print graphics, a PNG file contains a single image in an extensible structure of chunks, encoding the basic pixels and other information such as textual comments and integrity checks. PNG files nearly always use file extension PNG or png and are assigned MIME media type image/png, PNG was approved for this use by the Internet Engineering Steering Group on 14 October 1996, and was published as an ISO/IEC standard in 2004. In this thread, Oliver Fromme, author of the popular DOS JPEG viewer QPEG, proposed the PING name, meaning PING is not GIF, although GIF allows for animation, it was decided that PNG should be a single-image format. In 2001, the developers of PNG published the Multiple-image Network Graphics format, MNG achieved moderate application support, but not enough among mainstream web browsers and no usage among web site designers or publishers. In 2008, certain Mozilla developers published the Animated Portable Network Graphics format with similar goals,1 October 1996, Version 1.0 of the PNG specification was released, and later appeared as RFC2083. It became a W3C Recommendation on 1 October 1996,31 December 1998, Version 1.1, with some small changes and the addition of three new chunks, was released. 11 August 1999, Version 1.2, adding one extra chunk, was released,10 November 2003, PNG became an International Standard. This version of PNG differs only slightly from version 1.2, the original PNG specification was authored by an ad-hoc group of computer graphics experts and enthusiasts. Discussions and decisions about the format were done exclusively via email, a chunk consists of four parts, length, chunk type/name, chunk data and CRC. The CRC is a network-byte-order CRC-32 computed over the type and chunk data. Chunk types are given a case sensitive ASCII type/name, compare FourCC. The case of the different letters in the name is a bit field that provides the decoder with some information on the nature of chunks it does not recognize, the case of the first letter indicates whether the chunk is critical or not. If the first letter is uppercase, the chunk is critical, if not, critical chunks contain information that is necessary to read the file. If a decoder encounters a critical chunk it does not recognize, the case of the second letter indicates whether the chunk is public or private. Uppercase is public and lowercase is private and this ensures that public and private chunk names can never conflict with each other. The third letter must be uppercase to conform to the PNG specification and it is reserved for future expansion
16.
Alpha compositing
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In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, for example, compositing is used extensively when combining computer-rendered image elements with live footage. In order to combine these image elements correctly, it is necessary to keep an associated matte for each element. To store matte information, the concept of a channel was introduced by Alvy Ray Smith in the late 1970s. In a 2D image element, which stores a color for each pixel, additional data is stored in the alpha channel with a value between 0 and 1. A value of 0 means that the pixel does not have any information and is transparent. A value of 1 means that the pixel is opaque because the geometry completely overlapped the pixel, if an alpha channel is used in an image, there are two common representations that are available, straight alpha, and premultiplied alpha. With straight alpha, the RGB components represent the color of the object or pixel, with premultiplied alpha, the RGB components represent the color of the object or pixel, adjusted for its opacity by multiplication. A more obvious advantage of this is that, in certain situations, however, the most significant advantages of using premultiplied alpha are for correctness and simplicity rather than performance, premultiplied alpha allows correct filtering and blending. In addition, premultiplied alpha allows regions of alpha blending. Assuming that the color is expressed using straight RGBA tuples. If the color were fully green, its RGBA would be, however, if this pixel uses premultiplied alpha, all of the RGB values are multiplied by 0.5 and then the alpha is appended to the end to yield. In this case, the 0.5 value for the G channel actually indicates 100% green intensity, for this reason, knowing whether a file uses straight or premultiplied alpha is essential to correctly process or composite it. Premultiplied alpha has some advantages over normal alpha blending because premultiplied alpha blending is associative. Moreover, premultiplied alpha has a representation for transparent pixels. Ordinary interpolation without premultiplied alpha leads to RGB information leaking out of fully transparent regions, when interpolating or filtering images with abrupt borders between transparent and opaque regions, this can result in borders of colors that were not visible in the original image. Errors also occur in areas of semitransparancy because the RGB components are not correctly weighted, with the existence of an alpha channel, it is possible to express compositing image operations using a compositing algebra. For example, given two image elements A and B, the most common compositing operation is to combine the images such that A appears in the foreground and this can be expressed as A over B
17.
Stylish
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A user style may be more or less selective, targeting one specific web page, or several, or all of the pages on one or more domains, or every page on the web. Mozilla-based web browsers and Chromium-based browsers are supported with multiple implementations of the extension, a similar but unrelated extension provides the same functionality in Apple Safari. Firefox for Android users can download the add-on, but creating and editing styles is not supported. All can download and install stylesheets from a website, where members can upload. User styles are CSS style sheets designed to alter the appearance of one, some, Stylish for Firefox can additionally style the skin of the browser itself, but the Android version does not support this because the user interface is built in native Android code. The styles are applied only to the targets specified, individual user styles can be enabled or disabled without having to restart the browser. User styles are added to the CSS rules provided by the site, the most common uses are ad-blocking, applying a new color scheme, and eliminating unwanted page elements. There are three classes of user styles, site styles change the appearance of a particular web site. Global styles change the appearance of all web sites, app styles change the appearance of the Firefox user interface, only supported on Firefox. It is similar to the userChrome. css CSS file used by Firefox, Stylish is often compared to Greasemonkey, another Mozilla extension that allows client-side manipulation of web pages. Greasemonkeys user scripts are essentially dynamically inserted JavaScript that can alter a pages appearance or functionality, while Stylish uses CSS, userstyles. org holds user-submitted styles, most of which can be converted to Greasemonkey scripts. These also have the option of being added to Greasemonkey
18.
Spatial anti-aliasing
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In digital signal processing, spatial anti-aliasing is the technique of minimising the distortion artifacts known as aliasing when representing a high-resolution image at a lower resolution. Anti-aliasing is used in photography, computer graphics, digital audio. Anti-aliasing means removing signal components that have a higher frequency than is able to be resolved by the recording device. This removal is done before sampling at a lower resolution, when sampling is performed without removing this part of the signal, it causes undesirable artifacts such as the black-and-white noise near the top of figure 1-a below. In digital photography, optical anti-aliasing filters are made of birefringent materials, the anti-aliasing filter essentially blurs the image slightly in order to reduce the resolution to or below that achievable by the digital sensor. In computer graphics, anti-aliasing improves the appearance of polygon edges, however, it incurs a performance cost for the graphics card and uses more video memory. The level of anti-aliasing determines how smooth polygon edges are, Figure 1-a illustrates the visual distortion that occurs when anti-aliasing is not used. Near the top of the image, where the checker-board is very small, in contrast, Figure 1-b shows an anti-aliased version of the scene. The checker-board near the top blends into grey, which is usually the effect when the resolution is insufficient to show the detail. Even near the bottom of the image, the edges appear much smoother in the anti-aliased image, Figure 1-c shows another anti-aliasing algorithm, based on the sinc filter, which is considered better than the algorithm used in 1-b. Figure 2 shows magnified portions of Figure 1-a and 1-c for comparison, in Figure 1-c, anti-aliasing has interpolated the brightness of the pixels at the boundaries to produce grey pixels since the space is occupied by both black and white tiles. These help make Figure 1-c appear much smoother than Figure 1-a at the original magnification, anti-aliasing is often applied in rendering text on a computer screen, to suggest smooth contours that better emulate the appearance of text produced by conventional ink-and-paper printing. Particularly with fonts displayed on typical LCD screens, it is common to use subpixel rendering techniques like ClearType, sub-pixel rendering requires special colour-balanced anti-aliasing filters to turn what would be severe colour distortion into barely-noticeable colour fringes. Pixel geometry affects all of this, whether the anti-aliasing and sub-pixel addressing are done in software or hardware and it is a fairly fast function, but it is relatively low-quality, and gets slower as the complexity of the shape increases. For purposes requiring very high-quality graphics or very complex vector shapes, note, The DrawPixel routine above cannot blindly set the colour value to the percent calculated. It must add the new value to the value at that location up to a maximum of 1. Otherwise, the brightness of each pixel will be equal to the darkest value calculated in time for that location which produces a bad result. In this approach, the image is regarded as a signal
19.
Blackle
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Blackle is a website powered by Google Custom Search and created by Heap Media, which aims to save energy by displaying a black background and using grayish-white font color for search results. Blackle claims having saved nearly 6 MWh of electrical energy up to December 2016, for comparison, the average American household consumes 11 MWh of electrical energy per year. The concept behind Blackle is that computer monitors can be made to use less energy by displaying much darker colors, Blackle is based on a study which tested a variety of CRT and LCD monitors. There is dispute over whether there really are any energy saving effects, especially for users of LCD screens, where there is a constant backlight. This concept was first brought to the attention of Heap Media by a blog post, the homepage of Blackle provides a count of the number of watt hours claimed to have been saved by enabling this concept
20.
Color
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Color or colour is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them and this reflection is governed by the objects physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, there may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a colours colorfulness). The photo-receptivity of the eyes of species also varies considerably from our own. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red, papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or simply color science and it includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its wavelength and its intensity, when the wavelength is within the visible spectrum, it is known as visible light. Most light sources emit light at different wavelengths, a sources spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, in each such class the members are called metamers of the color in question. The table at right shows approximate frequencies and wavelengths for various pure spectral colors, the wavelengths listed are as measured in air or vacuum. A common list identifies six main bands, red, orange, yellow, green, blue, Newtons conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Some objects not only light, but also transmit light or emit light themselves. This effect is known as color constancy, opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with roughly equal strength, they appear white, if they absorb all wavelengths, they appear black. Opaque objects that reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences
21.
Shades of red
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Varieties of the color red may differ in hue, chroma or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a red or other hue mixed with white, a large selection of these various colors is shown below. At right is displayed the web color pink, a tint of red. The pink is considered to be a basic color term on its own. At right is displayed the tone of salmon that is called salmon in Crayola crayons. This color was introduced by Crayola in 1949, see the List of Crayola crayon colors. The color coral pink is displayed at right, an orange color. The web color salmon is displayed at right, the color displayed at right, Red, RGB red, or electric red is the brightest possible red that can be reproduced on a computer monitor. This color is an approximation of a red spectral color. It is one of the three colors of light in the RGB color model, along with green and blue. Portable devices such as mobile phones might have even narrower gamut due to this purity–power tradeoff and their red may be less colorful and this color is also the color called red in the X11 web colors, which were originally formulated in 1987. It is also called color wheel red and it is at precisely zero degrees on the HSV color wheel, also known as the RGB color wheel. Pigment red is the red that is achieved by mixing process magenta. This is the red that is shown in the diagram located at the bottom of the following website offering tintbooks for CMYK printing. The purpose of the CMYK color system is to provide the maximum possible gamut of colors capable of being reproduced in printing. Psychedelic art made people used to brighter colors of red, the result approximates the electric red shown above. The color defined as red in the NCS or Natural Color System is shown at right, the Natural Color System is a color system based on the four unique hues or psychological primary colors red, yellow, green, and blue. The NCS is based on the opponent process theory of vision, the Natural Color System is widely used in Scandinavia
22.
Shades of orange
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In optics, orange has a wavelength between approximately 585 and 620 nm and a hue of 30° in HSV color space. In the RGB color space it is a tertiary color numerically halfway between gamma-compressed red and yellow, as can be seen in the RGB color wheel, the complementary color of orange is azure. Orange pigments are largely in the ochre or cadmium families, varieties of the color orange may differ in hue, chroma or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being an orange or other hue mixed with white, a large selection of these various colors is shown below. At right is the orange, also known as color wheel orange. This is the tone of orange that is a pure chroma on the HSV color wheel, the complementary color of orange is azure. At right is the web color called orange and it is defined in CSS as the hex triplet FFA500. The web color called dark orange is at the right, at right is displayed the color that is called orange in Pantone. The source of color is the Pantone Textile Paper eXtended color list. At right is displayed the color that is called orange by Crayola, orange was one of the original colors formulated by Crayola in 1903. Displayed at right is the web color papaya whip, a tint of orange. Papaya whip is a representation of the color that would result if mashed papayas were blended with ice cream, whipped cream. At right is displayed the color peach, the first recorded use of peach as a color name in English was in 1588. Displayed at right is the light orange. This color was formulated for Crayola colored pencils, at right is displayed the color apricot. Apricot has been in use as a name since 1851. Displayed at right is the color melon and this color is a representation of the color of the interior flesh of a cantaloupe, the most commonly consumed melon. The first recorded use of melon as a name in English was in 1892
23.
Shades of yellow
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Varieties of the color yellow may differ in hue, chroma or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a yellow or other hue mixed with white, a large selection of these various colors is shown below. Displayed at right is the web color light yellow, displayed at right is the web color cream, a pale tint of yellow. Displayed at right is the web color lemon chiffon Lemon chiffon is a color that is reminiscent of the color of lemon chiffon cake. The color box at right shows the most intense yellow representable in 8-bit RGB color model and this color is also called color wheel yellow. It is at precisely 60 degrees on the HSV color wheel, process yellow, also known as canary yellow, is one of the three colors typically used as subtractive primary colors, along with magenta and cyan. Process yellow is not an RGB color, and in the CMYK color model there is no fixed conversion from CMYK primaries to RGB, different formulations are used for printers ink, so there can be variations in the printed color that is pure yellow ink. The first recorded use of yellow as a color name in English was in 1789. The color defined as yellow in the NCS or Natural Color System is shown at right, the Natural Color System is a color system based on the four unique hues or psychological primary colors red, yellow, green, and blue. The NCS is based on the opponent process theory of vision, the “Natural Color System” is widely used in Scandinavia. The color defined as yellow in the Munsell color system is shown at right, in order for all the colors to be spaced uniformly, it was found necessary to use a color wheel with five primary colors—red, yellow, green, blue, and purple. The Munsell colors displayed are only approximate as they have adjusted to fit into the sRGB gamut. The color that is called yellow in Pantone is displayed at right, the source of this color is the Pantone Textile Paper eXtended color list, color #C, EC, M, PC, U, or CP—Yellow. The color that is called yellow in Crayola crayons is displayed at right, Yellow was one of the original Crayola colors formulated in 1903. The color unmellow yellow is shown at right, the color unmellow yellow was formulated by Crayola in 1990. The color unmellow yellow is a fluorescent yellow to Laser Lemon. In crayons, the color may look a little bit orange-ish, the color is supposed to be fluorescent, but there is no mechanism to display fluorescence on a flat computer screen. Lemon is a color somewhat resembling yellow and named after the fruit, the color lemon is a representation of the color of the outer skin of a lemon
24.
Shades of green
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Varieties of the color green may differ in hue, chroma or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a green or other hue mixed with white, a large selection of these various colors is shown below. Green is common in nature, especially in plants, many plants are green mainly because of a complex chemical known as chlorophyll which is involved in photosynthesis. Many shades of green have been named after plants or are related to plants, due to varying ratios of chlorophylls, the plant kingdom exhibits many shades of green in both hue and value. Artichoke is a color that is a representation of the color of a raw fresh uncooked artichoke, another name for this color is artichoke green. The first recorded use of green as a color name in English was in 1905. This is the color called green in Pantone. The source is Pantone 18-0125 TPX Asparagus is a tone of green that is named after the vegetable, Crayola created this color in 1993 as one of the 16 to be named in the Name the Color Contest. It is also the color of a wild asparagus plant blowing in the wind of the 1949 classic film Sands of Iwo Jima, another name for this color is asparagus green. The first recorded use of green as a color name in English was in 1805. Avocado is a color that is a representation of the color of the surface of an avocado. The color avocado is a dark yellow-green color, avocado was a common color for metal surfaces, as well as the color harvest gold, during the whole decade of the 1970s. They were both also popular colors for shag carpets, both colors went out of style by the early 1980s. Dark green is a shade of green. A different shade of green has been designated as green for certain computer uses. Fern green is a color that resembles ferns, a Crayola crayon named fern was created in 1998, which is a lighter shade of the top color shown on the right. The first recorded use of green as a color name in English was in 1902. Forest green refers to a green color said to resemble the color of the trees, the first recorded use of forest green as the name of a color in the English language was in 1810
25.
Shades of cyan
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This article is about notable tints and shades of the color cyan, a greenish blue. Cyan is one of the subtractive primary colors- cyan, magenta, the first recorded use of cyan blue as a color name in English was in 1879. As such, the CMYK printing process was invented in the 1890s, process cyan is not an RGB color, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for ink, so there can be variations in the printed color that is pure cyan ink. A typical formulation of process cyan is shown in the box at right. The source of the color shown at right is the color magenta that is shown in the located at the bottom of the following website offering tintbooks for CMYK printing. The X11 name for this color is cyan, the HTML name for the color is aqua. They are both composed of the mixture of blue and green light, and are exactly the same color. See also Air Force blue#Aero Aero blue is a fluorescent cyan color, Aero blue was used as rainshower in one of the Sharpie permanent markers but not as bright on the marker. However, there is no mechanism for showing fluorescence on a computer screen, aquamarine is a color that is a bluish tint of cerulean toned toward cyan. It is named after the mineral aquamarine, a gemstone found in granite rocks. The first recorded use of aquamarine as a name in English was in 1598. Blue-green has been a Crayola color since 1930, displayed at right is the color caribbean current. At right is displayed the color celeste, bleu celeste is a rarely occurring tincture in heraldry. This tincture is sometimes also called ciel or simply celeste and it is depicted in a lighter shade than the range of shades of the more traditional tincture azure, which is the standard blue used in heraldry. It has been used rarely since the 17th century, gaining popularity after the First World War, the first recorded use of cerulean as a color name in English was in 1590. The word is derived from the Latin word caeruleus, dark blue, blue, or blue-green. Charleston green is a dark shade of cyan
26.
Shades of blue
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Varieties of the color blue may differ in hue, chroma, or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a blue or other hue mixed with white, a large selection of these various colors is shown below. In this section, the term tint is used in its sense as used in color theory. Baby blue is known as one of the pastel colors, with a hue code of 199, this color is a tone of azure. The first recorded use of blue as a color name in English was in 1892. The web color blue is displayed in the color box at right. Variations of this color are known as sky blue, baby blue, within the X11 color system, with a hue code of 194, this color is closer to cyan than to blue. The first recorded use of blue as a color term in English is in the year 1915. Shown in the right is the color periwinkle, or periwinkle blue, another name for this color is lavender blue. The color is a mixture of white and blue and it is named after the Periwinkle flower and is also commonly referred to as a tone of light blue. The web color blue is shown on the right. The first recorded use of blue as a color name in English was in 1774. Displayed at right is the color morning blue and it is a representation of the color of the morning sky. The year the first recorded use of morning blue as a name in English is unknown. Source of color, ISCC-NBS Dictionary of Color Names --Color Sample of Morning Blue The color defined as blue in the RGB color model and this color is the brightest possible blue that can be reproduced on a computer screen, and is the color named blue in X11. It is one of the three colors used on the RGB color space, along with red and green. This color is called color wheel blue. It is at precisely 240 degrees on the HSV color wheel and it is a spectral color which lies at, or near, the short-wave end of the traditional blue and possibly was classified as indigo by Newton
27.
Indigo
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Indigo is a deep and rich color close to the color wheel blue, as well as to some variants of ultramarine. The color indigo is named after the indigo dye derived from the plant Indigofera tinctoria, the first known recorded use of indigo as a color name in English was in 1289. Species of Indigofera were cultivated in Peru, India, East Asia, the earliest direct evidence for the use of indigo dates to around 4000 BCE and comes from Huaca Prieta, in contemporary Peru. Pliny mentions India as the source of the dye, imported in small quantities via the Silk Road, the Greek term for the dye was Ἰνδικὸν φάρμακον, which, adopted to Latin as indicum and via Portuguese gave rise to the modern word indigo. El Salvador has lately been the biggest producer of indigo, Indigo was actually a plant that got its name because it came from the Indus Valley, discovered some 5,000 years ago, where it was called nila, meaning dark blue. And by the 7th Century BC, people starting using the plant as a dye — the Mesopotamians were even carving out recipes for making indigo dye onto clay tablets for record-keeping. By 1289, knowledge of the dye made its way to Europe, but it wasn’t until 1640 when demand started to pick up for indigo. Spanish explorers discovered an American species of Indigo and began to cultivate the product in Guatemala, the English and French subsequently began to encourage indigo cultivation in their colonies in the West Indies. Indigo dye could be made from two different types of plants — the indigo plant, which produced the best results, the British were producing indigo with woad, a plant that yielded a lesser quality dye, but a plant they could grow. They even tried to hold their monopoly on indigo dye by managing to ban the indigo plant for years, but eventually the British began to focus on tea and other crops — and meanwhile, the French started to get their fair share of the market. The French had gone to war with Britain, so the British could hardly rely on the French for this precious blue dye, consequently, the British had to turn to their colonies in America. It was Eliza Lucas from South Carolina who figured out how to grow the indigo plant, the same indigo dye is contained in the woad plant, Isatis tinctoria, for a long time the main source of blue dye in Europe. Woad was replaced by true indigo as trade routes opened up, the Early Modern English word indigo referred to the dye, and not to the color itself, and indigo is not traditionally part of the basic color-naming system. Modern sources place indigo in the spectrum between 420 and 450 nanometers, which lies on the side of color wheel blue. However, the correspondence of this definition with colors of actual indigo dyes is disputed, isaac Newton introduced indigo as one of the seven base colors of his work. In a pivotal experiment in the history of optics, the young Newton shone a narrow beam of sunlight through a prism to produce a band of colors on the wall. He linked the seven prismatic colors to the seven notes of a major scale, as shown in his color wheel, with orange. Indigo is therefore counted as one of the colors of the rainbow
28.
Shades of violet
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There are numerous variations of the color violet, a sampling of which are shown below. The tertiary color on the HSV color wheel halfway between blue and magenta is called color wheel violet. This tone of violet—an approximation of the color violet at about 417 nanometers as plotted on the CIE chromaticity diagram—is shown at right. This tone of violet is actually somewhat toward indigo assuming indigo is accepted as a separate spectrum color, another name for this color is near violet. The color at right, electric violet, is the closest approximation to middle spectrum violet that can be made on a screen, given the limitations of the sRGB color gamut. Other names for this color are middle violet or simply violet, displayed at right is the color vivid violet, a color approximately equivalent to the violet seen at the extreme edge of human visual perception. When plotted on the CIE chromaticity diagram, it can be seen that this is a hue corresponding to that of a stimulus of approximately 380 nm on the spectrum. Thus another name for this color is extreme violet, the so-called web color violet is in actuality not really a tint of violet, a spectral color, but is a non-spectral color. This same color appears as violet in the X11 color names, mauve is a color that is named after the mallow flower. Another name for the color is mallow with the first recorded use of mallow as a name in English in 1611. Since the color mauve has a hue code of 276, it may be regarded as a tone of violet. At right is displayed the color lavender and this color may also be called lavender or floral lavender to distinguish it from the web color lavender. It is the color of the part of the lavender flower. The first recorded use of the word lavender as a term in English was in 1705. Since the color lavender has a hue code of 275, it may be regarded as a tone of violet. At right is displayed the color French violet, which is the tone of violet that is called violet in the Pourpre. com color list, the color African violet is displayed at right. The source of color is the Pantone Textile Paper eXtended color list. The color Chinese violet is displayed at right, the first recorded use of Chinese violet as a color name in English was in 1912
29.
Shades of purple
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There are numerous variations of the color purple, a sampling of which are shown below. In common English usage, purple is a range of hues of color occurring between red and blue. In color theory, purple colors are any colors on the line of purples on the CIE chromaticity diagram, the first recorded use of purple as a color name in English was in 975 AD. Therefore, Tyrian purple was also called imperial purple, Tyrian purple may have been discovered as early as the time of the Minoan civilization. Alexander the Great, the emperor of the Seleucid Empire, the imperial robes of Roman emperors were Tyrian purple trimmed in metallic gold thread. The badge of office of a Roman Senator was a stripe of Tyrian purple on their white toga, Tyrian purple was continued in use by the emperors of the Eastern Roman Empire until its final collapse in 1453. The actual tone could vary depending on how it was formulated, lesser royal houses that wanted to economize could mix the Tyrian purple dye with the much cheaper indigo to create a color closer to violet. Han purple is a type of pigment found in China between 500 BC and AD220. It was used in the decoration of the Terracotta Army, the color royal purple is shown at right. This tone of purple is bluer than the ancient Tyrian purple, the first recorded use of royal purple as a color name in English was in 1661. In 1990, royal purple was formulated as one of the Crayola crayon colors, mauveine was first named in 1856. Chemist Sir William Henry Perkin, then eighteen, was attempting to create artificial quinine, an unexpected residue caught his eye, which turned out to be the first aniline dye—specifically, Perkins mauve or mauveine is sometimes called aniline purple. Perkin was so successful in recommending his discovery to the industry that his biography by Simon Garfield is titled Mauve. As mauveine faded easily, our understanding of mauve is as a lighter. Mauveine was named after the mauve colored mallow flower, even though it is a deeper tone of purple than mauve. The term Mauve in the late 19th century could refer to either the deep, Mauve came into great vogue when in 1862 Queen Victoria appeared at the Royal Exhibition in a mauve silk gown—dyed with mauveine. By 1890, this color had become so pervasive in fashion that author Thomas Beer used it in the title of his book about the 1890s, The Mauve Decade. This red-violet color, called purple by artists, is the pigment color that would be on a pigment color color wheel between pigment violet and pigment magenta
30.
Shades of magenta
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This article is about notable tints and shades of the color magenta. These various colors are shown below, Magenta is a color made up of equal parts of red and blue light. This would be the definition of the color as defined for computer display. It is a pure chroma on the RGB color wheel midway between violet and rose, in HSV color space, magenta has a hue of 300°. Magenta is not a spectral but a color, it cannot be generated by light of a single wavelength. Humans, being trichromats, can see as far as 380 nanometers into the spectrum. The hue magenta is the complement of green, magenta pigments absorb green light, thus magenta, besides being called original magenta, magenta dye color is also called rich magenta to distinguish it from the colors printers magenta and electric magenta, shown below. Magenta was one of the first aniline dyes, discovered shortly after the Battle of Magenta, the color was originally called fuchsine or roseine, but for marketing purposes in 1860 the color name was changed to magenta after the battle. Hence, the color is named indirectly after the town, as such, the CMYK printing process was invented in the 1890s, when newspapers began to publish color comic strips. Process magenta is not an RGB color, and there is no fixed conversion from CMYK primaries to RGB, different formulations are used for printers ink, so there can be variations in the printed color that is pure magenta ink. A typical formulation of process magenta is shown in the box at right. The source of the color shown at right is the color magenta that is shown in the located at the bottom of the following website offering tintbooks for CMYK printing. Magenta, shown at the right, is one of the three colors in the RGB color model, used to make all the colors on computer. It is made by a mixture of red and blue light at equal intensity and it is called magenta on X11 list of color names, and fuchsia on the HTML color list. The web colors magenta and fuchsia are exactly the same color, sometimes the web color magenta is called electric magenta or electronic magenta. Amaranth is a color that is a representation of the color of the flower of the amaranth plant. The color amaranth purple is displayed at right, at right is displayed a Crayola color formulated in 1949, it was originally called brilliant rose but the name was changed in 1958 to magenta. This color has a hue angle of 329, which is close to the hue angle of the color rose, displayed at right is the Crayola color shocking pink
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Shades of pink
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This article is about notable tints and shades of the color pink. These various colors are shown below, at right is displayed the web color pink. At right is displayed the web color light pink, the name of the web color is written as lightpink in HTML for computer display. Although this color is called pink, as can be ascertained by inspecting its hex code, it is actually a slightly deeper, not a lighter. A more accurate name for it in terms of color nomenclature would therefore be medium light pink. At right is displayed the web color hot pink, the name of the web color is written as hotpink in HTML for computer display. At right is displayed the web color deep pink, the name of the web color is written as deeppink in HTML for computer display. Displayed at right is the color champagne pink, the source of this color is the Pantone Textile Paper eXtended color list, color #12-1107 TPX—Champagne Pink. At right is displayed the color pink lace, the color name pink lace for this pale tone of rose pink has been in use since 2001, when it was promulgated as one of the colors on the Xona. com Color List. This color is suggestive of the color of womens lingerie. The color piggy pink is displayed at right, the color piggy pink is a representation of the color of a pink pig. The color piggy pink was formulated by Crayola in 1998, the color was originally called pig pink, but later the name was changed to piggy pink. At right is displayed the pale pink, a light. At right is displayed the color pink, a light shade of pink. The first recorded use of pink as a color name in English was in 1928. This is a recent tradition, however, and until the 1940s the convention was exactly the opposite, pink was used for boys while girls were dressed in blue. Spanish pink is the color that is called Rosa in the Guía de coloraciones by Rosa Gallego and Juan Carlos Sanz, at right is displayed the color cameo pink, a medium light tone of rose pink. The first recorded use of pink as a color name in English was in 1912
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Shades of brown
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Brown is a composite color which can be produced by combining red, yellow, and black, or by a combination of orange and black—as can be seen in the color box at right. The color brown shown at right has a hue code of 30, in the RGB color model used to create all the colors on computer and television screens, brown is made by combining red and green light at different intensities. Brown color names are not very precise, and some shades, such as beige, can refer to a wide variety of colors. Browns are usually described as light or dark, reddish, yellowish, there are no standardized names for shades of brown, the same shade may have different names on different color lists, and sometimes the one name can refer to several very different colors. The X11 color list of web colors lists seventeen different shades of brown, brown colors are dark or muted shades of reds, oranges, and yellows which are created on computer and television screens using the RGB color model and in printing with the CMYK color model. Browns can also be created by mixing two complementary colors from the RYB color model, below is a list of some of the common brown colors. The web color called brown is displayed at right, the historical and traditional name for this color is red-brown. The color shown above at the top right at the head of this article is the color normally and traditionally regarded as brown—a medium dark orange and its h code is 30, which signifies a shade of orange. The color to the right that was chosen as the web color brown—a medium dark red—is the color traditionally called red-brown. That this color is a shade of red and not orange can be ascertained by inspecting its h code. The first recorded use of red-brown as a name in English was in 1682. Beaver is a color that is a representation of the color of the fur of a beaver. The first recorded use of beaver as a name in English was in 1705. The color beaver was formulated as one of the Crayola colors in 1998, etymologically, its believed that the words brown and beaver ultimately stem from the same root word. Beige is a color that is a representation of the color of unbleached wool, buff is a pale yellow-brown color that got its name from the colour of buffed leather. According to the Oxford English Dictionary, buff as a descriptor of a colour was first used in the London Gazette of 1686, burnt umber is made by heating raw umber, which dehydrates the iron oxides and changes them partially to the more reddish hematite. It is used for oil and water color paint. The first recorded use of burnt umber as a name in English was in 1650
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Shades of white
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Shades of white are colors that differ only slightly from pure white. Variations of white include what are commonly termed off-white colors, which may be considered part of a color scheme. In color theory, a shade is a pure color mixed with black, strictly speaking, a “shade of white” would be a neutral gray. This article is also about off-white colors that vary from white in hue. Colors often considered shades of white include, cream, eggshell, ivory, Navajo white, even the lighting of a room, however, can cause a pure white to be perceived as off-white. Off-white colors were pervasively paired with beiges in the 1930s, whiteness measures the degree to which a surface is white in colorimetry. Below is a showing the computer web color shades of white. An achromatic white is a color in which the red, green. The web colors white and white smoke are achromatic colors, a chromatic shade of white is a white color in which the red, green, and blue codes are not exactly equal, but are close to each other, which is what makes it a shade of white. A white visual stimulation will be void of hue and grayness, white is the lightest possible color. The web color ghost white is a tint of white associated with what it is imagined the color of a ghost might be, there is no evidence that this color name was in use before the X11 color names were formulated in 1987. The web color white smoke is displayed on the left, there is no evidence that this color name was in use before the X11 color names were formulated in 1987. The Crayola crayon color baby powder was introduced in 1994 as part of its specialty Magic Scent crayon collection, the web color snow is displayed at left. The first recorded use of snow as a name in English was in 1000. The color snow was included as one of the X11 colors when they were formulated in 1987, ivory is an off-white color that resembles ivory, the material out of which the teeth and tusks of animals are made. It has a slight tint of yellow. The first recorded use of ivory as a name in English was in 1385. The color ivory was included as one of the X11 colors when they were formulated in 1987, the web color floral white is displayed at left
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Shades of gray
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Variations of gray or grey include achromatic grayscale shades, which lie exactly between white and black, and nearby colors with low colorfulness. A selection of a number of various colors is shown below. Below is a showing the computer web color grays. An achromatic gray is a color in which the red, green. The web colors gray, gainsboro, light gray, dark gray, a chromatic gray is a gray color in which the red, green, and blue codes are not exactly equal, but are close to each other, which is what makes it a shade of gray. The colors white and black are not usually thought of as shades of gray, since achromatic colors have no hue, the hue code is left blank for achromatic colors. A white visual stimulation will be void of hue and grayness, white is the lightest possible color. Black is the color of objects that do not emit or reflect light in any part of the visible spectrum, black is the darkest possible color. Achromatic grays are colors in which the rgb values are exactly equal, since achromatic grays have no hue, the hue code is indicated with a dash. Achromatic grays are the axis of the sphere, with white at the north pole. The various tones of gray are along the axis of the color sphere from white at the top of the axis to black at the bottom of the axis. At right is displayed the web color gainsboro, gainsboro is a pale tone of gray. There is no evidence the name gainsboro was used as a name before it was included as one of the X11 colors when they were formulated in 1987. At right is displayed the web color light gray, displayed at right is the web color silver. This color is a representation of the color of the metal silver This is supposed to be a color, however. At right is displayed the color gray, or gray in the X11 color names. The coordinates in the X11 were set at 190 to avoid gray being displayed as white on 2-bit grayscale displays, see the chart Color names that clash between X11 and HTML/CSS in the X11 color names article to see those colors which are different in HTML/CSS and X11. At right is displayed the dark medium gray, or dark gray in the X11 color names
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Shades of black
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Shades of black are colors that differ only slightly from pure black. These colors have a low lightness, from photometric point of view, a color which differs slightly from black always has low relative luminance. Black and dark colors are powerful accent colors that suggest weight, dignity, formality. In color theory, a shade is a pure color mixed with black and it decreases its lightness while nearly conserving its chromaticity. Strictly speaking, a “shade of black” is always a pure black itself, unlike these, many off-black colors possess a hue and a colorfulness. Colors often considered shades of black onyx, black olive, charcoal, and jet. A black visual stimulation will be void of hue and grayness, Black is the darkest possible color. A black body is a physical body that absorbs all incident electromagnetic radiation. To the human eye it seems black, midnight blue is a dark shade of blue named for its resemblance to the identifiably blue color of a moonlit night sky on or near the night of a full moon. This is the X11 web color midnight blue and this color was originally called midnight. The first recorded use of midnight as a name in English was in 1915. At right is displayed the web color dim gray and this color is a dark tone of gray. The color name dim gray first came into use in 1987, after the invention of the World Wide Web in 1991, these colors became known as the X11 web colors. Displayed at right is the color ebony and this color is a representation of the color of the wood ebony, a tropical hardwood widely used to make fine furniture, notably for French kings. The first use of ebony as a name in English was in 1590. The color displayed at left matches the color called taupe referenced below in the 1930 book A Dictionary of Color. However, the word taupe is currently used to refer to lighter shades of taupe. The first use of taupe as a name in English was in the early 19th century
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Colorimetry
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Colorimetry is the science and technology used to quantify and describe physically the human color perception. Colorimetric equipment is similar to that used in spectrophotometry, some related equipment is also mentioned for completeness. A tristimulus colorimeter measures the values of a color. A spectroradiometer measures the spectral radiance or irradiance of a light source. A spectrophotometer measures the reflectance, transmittance, or relative irradiance of a color sample. A spectrocolorimeter is a spectrophotometer that can calculate tristimulus values, a densitometer measures the degree of light passing through or reflected by a subject. A color temperature meter measures the temperature of an incident illuminant. In digital imaging, colorimeters are tristimulus devices used for color calibration, accurate color profiles ensure consistency throughout the imaging workflow, from acquisition to output. Reflected color can be measured using a spectrophotometer, which takes measurements in the region of a given color sample. If the custom of taking readings at 10 nanometer increments is followed and these readings are typically used to draw the samples spectral reflectance curve —the most accurate data that can be provided regarding its characteristics. The readings by themselves are not as useful as their tristimulus values. For this purpose, a spectrocolorimeter may be used, a spectrocolorimeter is simply a spectrophotometer that can estimate tristimulus values by numerical integration. On the other hand, tristimulus colorimeters are purpose-built, cheaper, the CIE recommends using measurement intervals under 5 nm, even for smooth spectra. Sparser measurements fail to accurately characterize spiky emission spectra, such as that of the red phosphor of a CRT display, photographers and cinematographers use information provided by these meters to decide what color balancing should be done to make different light sources appear to have the same color temperature. Internally the meter is typically a silicon photodiode tristimulus colorimeter, photometry Radiometry Schanda, János D. Colorimetry. Gardner, James L. Comparison of Calibration Methods for Tristimulus Colorimeters, journal of Research of the National Institute of Standards and Technology. Overview of the development and applications of colorimetry, optronik - Photometers An informative brochure with background information and specifications of their equipment. The section provides information on numerical scales and indices that are used throughout the world to remove subjective measurements, TS NIST Publications related to colorimetry
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Electromagnetic spectrum
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The electromagnetic spectrum is the collective term for all known frequencies and their linked wavelengths of the known photons. The electromagnetic spectrum of an object has a different meaning, and is instead the characteristic distribution of radiation emitted or absorbed by that particular object. Visible light lies toward the end, with wavelengths from 400 to 700 nanometres. The limit for long wavelengths is the size of the universe itself, until the middle of the 20th century it was believed by most physicists that this spectrum was infinite and continuous. Nearly all types of radiation can be used for spectroscopy, to study. Other technological uses are described under electromagnetic radiation, for most of history, visible light was the only known part of the electromagnetic spectrum. The ancient Greeks recognized that light traveled in straight lines and studied some of its properties, the study of light continued, and during the 16th and 17th centuries conflicting theories regarded light as either a wave or a particle. The first discovery of electromagnetic radiation other than visible light came in 1800 and he was studying the temperature of different colors by moving a thermometer through light split by a prism. He noticed that the highest temperature was beyond red and he theorized that this temperature change was due to calorific rays that were a type of light ray that could not be seen. The next year, Johann Ritter, working at the end of the spectrum. These behaved similarly to visible light rays, but were beyond them in the spectrum. They were later renamed ultraviolet radiation, during the 1860s James Maxwell developed four partial differential equations for the electromagnetic field. Two of these equations predicted the possibility of, and behavior of, analyzing the speed of these theoretical waves, Maxwell realized that they must travel at a speed that was about the known speed of light. This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave, maxwells equations predicted an infinite number of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the electromagnetic spectrum. Maxwells predicted waves included waves at very low compared to infrared. Hertz found the waves and was able to infer that they traveled at the speed of light, Hertz also demonstrated that the new radiation could be both reflected and refracted by various dielectric media, in the same manner as light. For example, Hertz was able to focus the waves using a lens made of tree resin, in a later experiment, Hertz similarly produced and measured the properties of microwaves
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Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
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Rainbow
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A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc, Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. However, the observer sees only an arc formed by illuminated droplets above the ground. In a primary rainbow, the arc shows red on the outer part and this rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. In a double rainbow, an arc is seen outside the primary arc. A rainbow is not located at a distance from the observer. Thus, a rainbow is not an object and cannot be physically approached, indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems under or at the end of a rainbow, Rainbows span a continuous spectrum of colours. Rainbows can be caused by many forms of airborne water and these include not only rain, but also mist, spray, and airborne dew. Rainbows can be observed there are water drops in the air. Because of this, rainbows are seen in the western sky during the morning. The most spectacular rainbow displays happen when half the sky is dark with raining clouds. The result is a rainbow that contrasts with the darkened background. During such good visibility conditions, the larger but fainter secondary rainbow is often visible and it appears about 10° outside of the primary rainbow, with inverse order of colours. The rainbow effect is commonly seen near waterfalls or fountains. In addition, the effect can be created by dispersing water droplets into the air during a sunny day. Rarely, a moonbow, lunar rainbow or nighttime rainbow, can be seen on strongly moonlit nights, as human visual perception for colour is poor in low light, moonbows are often perceived to be white. It is difficult to photograph the complete semicircle of a rainbow in one frame, for a 35 mm camera, a wide-angle lens with a focal length of 19 mm or less would be required
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Visible spectrum
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The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century
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Spectral color
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A spectral color is a color that is evoked by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths, also known as monochromatic light. Every wavelength of light is perceived as a spectral color, in a continuous spectrum. The spectrum is divided into named colors, though any division is somewhat arbitrary. Traditional colors include, red, orange, yellow, green, blue, and violet. The division used by Isaac Newton, in his wheel, was, red, orange, yellow, green, blue, indigo and violet. In modern divisions of the spectrum, indigo is often omitted, if luminance is counted, then spectral colors form a surface, otherwise their locus is a curve in a two-dimensional chromaticity space. Theoretically, only RGB-implemented colors which might be really spectral are its primaries, red, green, some samples in the table below provide only rough approximations of spectral and near-spectral colors. Ranges of wavelengths and frequencies are only approximate, among some of the colors that are not spectral colors are, Grayscale colors, such as white, gray, and black. Any color obtained by mixing a gray-scale color and another color, violet-red colors, which in color theory include line of purples colors, and other variations of purple and red. Impossible colors, which can not be seen under normal viewing of light, such as over-saturated colors or colors that are seemingly brighter than white
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Chromophore
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A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed within a certain spectrum of visible light. The chromophore is a region in the molecule where the difference between two separate molecular orbitals falls within the range of the visible spectrum. Visible light that hits the chromophore can thus be absorbed by exciting an electron from its state into an excited state. In biological molecules that serve to capture or detect light energy, in the conjugated chromophores, the electrons jump between energy levels that are extended pi orbitals, created by a series of alternating single and double bonds, often in aromatic systems. Common examples include retinal, various food colorings, fabric dyes, pH indicators, lycopene, β-carotene, various factors in a chromophores structure go into determining at what wavelength region in a spectrum the chromophore will absorb. Lengthening or extending a conjugated system with more unsaturated bonds in a molecule will tend to shift absorption to longer wavelengths, woodward-Fieser rules can be used to approximate ultraviolet-visible maximum absorption wavelength in organic compounds with conjugated pi-bond systems. Some of these are metal complex chromophores, which contain a metal in a complex with ligands. Examples are chlorophyll, which is used by plants for photosynthesis and hemoglobin, the highly conjugated pi-bonding system of the macrocycle ring absorbs visible light. The nature of the metal can also influence the absorption spectrum of the metal-macrocycle complex or properties such as excited state lifetime. The tetrapyrrole moiety in organic compounds which is not macrocyclic but still has a conjugated pi-bond system still acts as a chromophore, examples of such compounds include bilirubin and urobilin, which exhibit a yellow color. An auxochrome is a group of atoms attached to the chromophore which modifies the ability of the chromophore to absorb light. Halochromism occurs when a substance changes color as the pH changes and this is a property of pH indicators, whose molecular structure changes upon certain changes in the surrounding pH. This change in structure affects a chromophore in the pH indicator molecule, because of their limited extent, the aromatic rings only absorb light in the ultraviolet region, and so the compound appears colorless in the 0-8 pH range. However, as the pH increases beyond 8.2, that central carbon becomes part of a double bond becoming sp2 hybridized and this makes the three rings conjugate together to form an extended chromophore absorbing longer wavelength visible light to show a fuchsia color. At pH ranges outside 0-12, other molecular structure changes result in other color changes, visual phototransduction Woodwards rules Chromatophore Pigment Photophore Fluorophore Litmus Biological pigment Causes of Color, physical mechanisms by which color is generated. High Speed Nano-Sized Electronics May be Possible with Chromophores - Azonano. com
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Structural coloration
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Structural coloration is the production of colour by microscopically structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments. For example, peacock feathers are pigmented brown, but their microscopic structure makes them also reflect blue, turquoise, and green light. Structural coloration was first observed by English scientists Robert Hooke and Isaac Newton, Young described iridescence as the result of interference between reflections from two or more surfaces of thin films, combined with refraction as light enters and leaves such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively, different colours therefore appear at different angles. Some cuts of meat also show structural coloration due to the exposure of the arrangement of the muscular fibres. Many of these photonic mechanisms correspond to elaborate structures visible by electron microscopy, in plants, brilliant colours are produced by structures within cells. In his 1704 book Opticks, Isaac Newton described the mechanism of the other than the brown pigment of peacock tail feathers. Thomas Young extended Newtons particle theory of light by showing that light could behave as a wave. He showed in 1803 that light could diffract from sharp edges or slits, Colours of the latter kind are often spoken of as structural colours, they are caused by the structure of the coloured surfaces. The metallic lustre of the feathers of birds, such as the humming birds, is due to the presence of excessively fine striae upon the surface of the feathers. Structural coloration is caused by interference effects rather than by pigments, Colours are produced when a material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the colours wavelength. Structural coloration is responsible for the blues and greens of the feathers of birds, as well as many butterfly wings. These are often iridescent, as in peacock feathers and nacreous shells such as of pearl oysters and this is because the reflected colour depends on the viewing angle, which in turn governs the apparent spacing of the structures responsible. Structural colours can be combined with pigment colours, peacock feathers are pigmented brown with melanin, iridescence, as explained by Thomas Young in 1803, is created when extremely thin films reflect part of the light falling on them from their top surfaces. The rest of the light goes through the films, and a part of it is reflected from their bottom surfaces. The two sets of reflected waves travel back upwards in the same direction, when the waves are one or more whole wavelength apart – in other words at certain specific angles, they add, giving a strong reflection. At other angles and phase differences, they can subtract, giving weak reflections, the thin film therefore selectively reflects just one wavelength – a pure colour – at any given angle, but other wavelengths – different colours – at different angles. So, as a structure like a butterflys wing or birds feather moves
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Animal coloration
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Animal coloration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are coloured, while others are hard to see. In some species, such as the peacock, the male has strong patterns, conspicuous colours and is iridescent, there are several separate reasons why animals have evolved colours. Camouflage enables an animal to remain hidden from view, some animals use flashes of colour to divert attacks by startling predators. Zebras may possibly use motion dazzle, confusing a predators attack by moving a bold pattern rapidly, some animals are coloured for physical protection, with pigments in the skin to protect against sunburn, while some frogs can lighten or darken their skin for temperature regulation. Finally, animals can be coloured incidentally, for example, blood is red because the haem pigment needed to carry oxygen is red. Animals coloured in these ways can have striking natural patterns, Animals produce colour in different ways. Pigments are particles of coloured material, chromatophores are cells containing pigment, which can change their size to make their colour more or less visible. Some animals, including butterflies and birds, have microscopic structures in scales, bristles or feathers which give them brilliant iridescent colours. Other animals including squid and some fish can produce light. Animals often use two or more of these together to produce the colours and effects they need. Animal coloration has been a topic of interest and research in biology for centuries, so each of those threads in the Microscope appears a large long body, consisting of a multitude of bright reflecting parts. According to Charles Darwins 1859 theory of selection, features such as coloration evolved by providing individual animals with a reproductive advantage. For example, individuals with slightly better camouflage than others of the species would, on average. Henry Walter Batess 1863 book The Naturalist on the River Amazons describes his extensive studies of the insects in the Amazon basin, the book introduced the concept of frequency-dependent selection, as when edible mimics are less frequent than the distasteful models whose colours and patterns they copy. In the book, Poulton also coined the term aposematism for warning coloration, which he identified in widely differing animal groups including mammals, bees and wasps, beetles, and butterflies. Frank Evers Beddards 1892 book, Animal Coloration, acknowledged that natural selection existed but examined its application to camouflage, mimicry, the book was in turn roundly criticised by Poulton. Hugh Bamford Cotts 500-page book Adaptive Coloration in Animals, published in wartime 1940, systematically described the principles of camouflage, the book contains hundreds of examples, over a hundred photographs and Cotts own accurate and artistic drawings, and 27 pages of references
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Spectral power distribution
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In radiometry, photometry and color science, a spectral power distribution measurement describes the power per unit area per unit wavelength of an illumination. More generally, the spectral power distribution can refer to the concentration, as a function of wavelength. Knowledge of the SPD is crucial for optical-sensor system applications, optical properties such as transmittance, reflectivity, and absorbance as well as the sensor response are typically dependent on the incident wavelength. The approximation is valid when the area and wavelength interval are small, the ratio of spectral concentration at a given wavelength to the concentration of a reference wavelength provides the relative SPD. The SPD can be used to determine the response of a sensor at a specified wavelength and this compares the output power of the sensor to the input power as a function of wavelength. The spectral power distribution over the spectrum from a source can have varying concentrations of relative SPDs. The interactions between light and matter affect the absorption and reflectance properties of materials and subsequently produces a color that varies with source illumination and this stems from the optical phenomenon called Rayleigh scattering which produces a concentration of shorter wavelengths and hence the blue color appearance. The human visual response relies on trichromacy to process color appearance, the spectral makeup of the source can also coincide with color temperature producing differences in color appearance due to the sources temperature. Spectral Power Distribution Curves, GE Lighting
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Color vision
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Color vision is the ability of an organism or machine to distinguish objects based on the wavelengths of the light they reflect, emit, or transmit. In essence, different people see the same illuminated object or light source in different ways, isaac Newton discovered that white light splits into its component colours when passed through a dispersive prism. Newton also found that he could recombine these colours by passing them through a different prism to make white light, the characteristic colours are, from long to short wavelengths, red, orange, yellow, green, blue, and purple. In very low levels, vision is scotopic, light is detected by rod cells of the retina. Rods are maximally sensitive to wavelengths near 500 nm, and play little, if any, in brighter light, such as daylight, vision is photopic, light is detected by cone cells which are responsible for colour vision. Cones are sensitive to a range of wavelengths, but are most sensitive to wavelengths near 555 nm, between these regions, mesopic vision comes into play and both rods and cones provide signals to the retinal ganglion cells. The shift in colour perception from dim light to daylight gives rise to differences known as the Purkinje effect, the perception of white is formed by the entire spectrum of visible light, or by mixing colours of just a few wavelengths in animals with few types of colour receptors. In humans, white light can be perceived by combining wavelengths such as red, green, perception of color begins with specialized retinal cells containing pigments with different spectral sensitivities, known as cone cells. In humans, there are three types of cones sensitive to three different spectra, resulting in color vision. Each individual cone contains pigments composed of opsin apoprotein, which is linked to either 11-cis-hydroretinal or more rarely 11-cis-dehydroretinal. The cones are conventionally labeled according to the ordering of the wavelengths of the peaks of their spectral sensitivities, short, medium and these three types do not correspond well to particular colors as we know them. For example, while the L cones have been referred to simply as red receptors, similarly, the S- and M-cones do not directly correspond to blue and green, although they are often described as such. The RGB color model, therefore, is a convenient means for representing color, two complementary theories of color vision are the trichromatic theory and the opponent process theory. Ewald Hering proposed the opponent process theory in 1872 and it states that the visual system interprets color in an antagonistic way, red vs. green, blue vs. yellow, black vs. white. Both theories are now accepted as valid, describing different stages in visual physiology, green ←→ Magenta and Blue ←→ Yellow are scales with mutually exclusive boundaries. In the same way that there cannot exist a slightly negative positive number, a range of wavelengths of light stimulates each of these receptor types to varying degrees. Yellowish-green light, for example, stimulates both L and M cones equally strongly, but only stimulates S-cones weakly, the brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light. The opsins present in the L and M cones are encoded on the X chromosome, the OPN1LW gene, which codes for the opsin present in the L cones, is highly polymorphic
