1996 RAVENSBURGER MIX N MATCH color game translucent discs vintage SEALED RARE

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Seller: sidewaysstairsco ✉️ (1,180) 100%, Location: Santa Ana, California, US, Ships to: US & many other countries, Item: 194886044235 1996 RAVENSBURGER MIX N MATCH color game translucent discs vintage SEALED RARE. Check out our other new and used items>>>>>HERE! (click me) FOR SALE: A fun and educational game of color 1996 RAVENSBURGER MIX N MATCH DETAILS: Players: 2-4 Ages: 4-8 Duration: Approximately 20 minutes Author: Christine Welz Made In: Germany Product No: 24 365 5 Contents: 8 Red (Magenta) Game Discs 8 Blue Game Discs 8 Yellow Game Discs 1 Game Board 1 Color Die 6 Prize Bears Game Rules A game of colors! Ravensburger's Mix N Match is a game of primary and secondary colors.  Players mix and match awesome looking primary colored translucent game discs to make secondary colors. For example if you mix the color blue with yellow - you get the color green. This simple yet challenging game encourages the learning of color combinations in a fun and hands-on way. You can you play the game as intended or arrange the translucent colored discs in a way to create fun designs and/or patterns - it's a game or activity! The game is designed for 2 to 4 players. Each game lasts for approximately 20 minutes. Discover and Learn Mix N Match is part of Ravensburger's "Discover and Learn" series. This particular collection of games includes some of the most successful play and learn style games. These games offer children a chance to play, have fun and at the same time learn important skills. R etired and hard to find! Ravensburger's Mix N Match was released in 1996 and has been retired (no longer made and sold in stores) for a long time now - making it a hard to find game, especially in this condition, and a rare Ravensburger product. Authored by Christine Welz! Mix N Match was fathomed by imaginative Ravensburger game designer, Christine Welz. Welz created/authored wonderful and educational games for kids exclusively for Ravensburger throughout the '90s. Christine had a hand in producing Balancing Bears (Rigolours), Pack And Stack, Treasure Quest, and Ferkel Vor! to name just a few. Original The Wee Loft sticker tag! The plastic shrink wrap has an old original price tag from The Wee Loft attached. The Wee Loft is a high end European toy shop, with two U.S. locations (Corona del Mar, California and Dana Point, California), that specializes in toys that stimulate creativity and imagination in children. CONDITION: New; sealed. Please see photos. *To ensure safe delivery all items are carefully packaged before shipping out* THANK YOU FOR LOOKING. QUESTIONS? JUST ASK. *ALL PHOTOS AND TEXT ARE INTELLECTUAL PROPERTY OF SIDEWAYS STAIRS CO. ALL RIGHTS RESERVED.* "Ravensburger AG is a German game and toy company, publishing house and market leader in the European jigsaw puzzle market.... History The company was founded by Otto Robert Maier with seat in Ravensburg, a town in Upper Swabia in southern Germany. He began publishing in 1883 with his first author contract. He started publishing instruction folders for craftsmen and architects, which soon acquired him a solid financial basis. His first board game appeared in 1884, named "Journey around the world". At the turn of the 20th century, his product line broadened to include picture books, books, children’s activity books, Art Instruction manuals, non-fiction books, and reference books as well as children’s games, Happy Families and activity kits. In 1900, the Ravensburger blue triangle trademark was registered with the Imperial Patent office. As of 1912, many board and activity games had an export version that was distributed to Western Europe, the countries of the Danube Monarchy as well as Russia. Before the First World War, Ravensburger had around 800 products. The publishing house was damaged during the Second World War and continued to produce games in the years of the reconstruction. The company focused on children's games and books and specialized books for art, architecture and hobbies, and from 1962 grew strongly. The company started to produce jigsaw puzzle games in 1964, and in the same year opened subsidiaries in Austria, France, Italy, the Netherlands, Switzerland and the United Kingdom. In 1977 the company split into a book publishing arm and a game publishing arm. Today there are approximately 1800 available books and 850 games as well as puzzles, hobby products and CD-ROM titles at Ravensburger and its subsidiaries, which include Alea for "hobby and ardent game players" and F.X. Schmid for games, playing cards and children's books. Ravensburger products are exported to more than fifty countries. Ravensburger also expanded to video games and television shows in the late 1990s by forming Ravensburger Interactive Media (Sold in 2002 to JoWooD Productions) and Ravensburger Film + TV (later renamed as RTV Family Entertainment in 2000, and spun-off as Your Family Entertainment in 2006), respectively. Under the label, F.X. Schmid, Ravensburger produce one of the only two packs of true Tarock cards in Germany: a 54-card pack of the Tarot Nouveau pattern with genre scenes and used for playing the Tarot game of Cego popular in the Black Forest region. In September 2010, Ravensburger broke Educa's record for the world's largest jigsaw puzzle of 24000 pieces.[1] Ravensburger's new puzzle design by late pop artist Keith Haring titled, "Keith Haring: Double Retrospect" breaks the Guinness Book of World Records measuring 17' × 6' (5.18 m x 1.82 m) built from 32000 pieces and comes with its own dolly cart for toting. Currently, the largest commercial puzzle in the world is Grafika's "Travel by Art" with 54000 pieces.[2][3] Ravensburger's currently largest puzzles are "Memorable Disney Moments" and "Making Mickey Magic" with 40320 pieces.[4] Swedish toy train company BRIO was acquired by the Ravensburger Group on 8 January 2015.[5] In 2017, Ravensburger acquired American game company Wonder Forge.[6] The company's North American division, Ravensburger NA, is based in Seattle, Washington and releases approximately 25 games per year, the most successfully of which so far is Villainous, based on various Disney properties.[7] Ravensbuger NA sold about 3 million copies of games in 2018.[7] Notable board games Games sold under the "Ravensburger" imprint:     Dingbats     Emoji     Enchanted Forest     Havannah     Java     Journey through Europe     Know Interactive Board Game     Labyrinth (board game)     Make 'n' Break     Malefiz     Mexica     The Name of the Rose (2008)[8]     Nobody is perfect     Quest     Reversi     Rivers, Roads & Rails     Scotland Yard     Star Wars     Tactil     Take It Easy     Tikal     Top Secret Spies     Villainous     What Do You Hear? Games sold under the "Alea" label:     Broom Service     Castles of Burgundy     Chinatown     Las Vegas     Princes of Florence     Puerto Rico     Ra     San Juan Games sold under the F.X. Schmid label:     Auf Achse     Torres Games sold under the "Ravensburger Digital" label:     Concentration in various editions" (wikipedia.org) "A tile-based game is a game that uses tiles as one of the fundamental elements of play. Traditional tile-based games use small tiles as playing pieces for gambling or entertainment games. Some board games use tiles to create their board, giving multiple possibilities for board layout, or allowing changes in the board geometry during play. Each tile has a back (undifferentiated) side and a face side. Domino tiles are usually rectangular, twice as long as they are wide and at least twice as wide as they are thick, though games exist with square tiles, triangular tiles and even hexagonal tiles.... Traditional games     Anagrams     Chinese dominoes     Dominoes     Mahjong Commercial games     Okey     Quad-Ominos     Qwirkle     Rummikub     Scrabble Games using non-rectangular tiles     Bendomino     Blokus     Gheos     Heroscape     Hive     Tantrix     Triominos Board games     Alhambra     Azul (board game)     Betrayal at House on the Hill     Carcassonne     Domineering     Fjords     Forbidden Island     Galaxy Trucker     Gold Mine     Rallyman: GT     Saboteur     The Settlers of Catan     Tsuro     Tsuro Of The Seas     Zombies!!!" (wikipedia.org) "Marek Richard Mann (also: Marek Mann) (* May 4, 1942 in Lemberg) is a German painter, graphic artist, illustrator and children's book author. Life [Edit | Edit source text] From 1962 to 1968 he studied graphics with Henryk Tomaszewski and Waclaw Waskowski, book illustration with Jan Marcin Szancer and painting with Juliusz Studnicki and Stanislaw Poznanski at the Academy of Fine Arts Warsaw. In 1968 he completed this with a master's degree. From 1967 to 1975 he worked as a painter, graphic artist and illustrator. From 1975 to 2016, Marek Mann worked as a freelance painter and graphic artist in Cologne. He designs posters, covers for plates, book covers, illustrates magazines and books, including 48 children's books, of which he is mostly also an author. As a jazz drummer, Mann participated in numerous concerts and music recordings. The "Jam Session" cycle is a connection between his two passions. [1] Marek Mann has been living and working in Brazil since 2016. Works " (wikipedia.org) "This is a list of games that used to be played by children, some of which are still being played today. Traditional children's games do not include commercial products such as board games but do include games which require props such as hopscotch or marbles (toys go in List of toys unless the toys are used in multiple games or the single game played is named after the toy; thus "jump rope" is a game, while "Jacob's ladder" is a toy). Despite being transmitted primarily through word of mouth due to not being considered suitable for academic study or adult attention, traditional games have, "not only failed to disappear but have also evolved over time into new versions."[1] Traditional children's games are defined, "as those that are played informally with minimal equipment, that children learn by example from other children, and that can be played without reference to written rules. These games are usually played by children between the ages of 7 and 12, with some latitude on both ends of the age range."[2] "Children's traditional games (also called folk games) are those that are passed from child to child, generation to generation, informally by word of mouth," and most children's games include at least two of the following six features in different proportion: physical skill, strategy, chance, repetition of patterns, creativity, and vertigo.... Tag games     Tag[4][5]         Ball tag         Chain tag         Cops and robbers (Cowboys and Indians)         Freeze tag[6]         Ghost in the graveyard         Kiss chase         Stuck in the mud     Blind man's buff[5]     British bulldogs (Sharks and minnows)     Capture the flag (Stealing Sticks)     Duck, duck, goose     Duck on a rock     Kabaddi     Kick the can     Marco Polo     Monkey on Woodchips (Grounders)     Patintero     Pie     Poison     Puss in the corner[6]     Ringolevio     Statues (red light, green light; Grandmother's Footsteps)     Tumbang preso     What's the time, Mr Wolf?     Chor Police Hiding games     Hide-and-go-seek[4][5]     Sardines[7] Games with equipment     Ball games[4][5]     Ball in a Cup     Baseball     Basketball     Beanbag toss     Catch     Conkers     Continuous cricket     Dandy shandy     Dodgeball     Football     Four Square (Kingey)     French cricket     Gaga     Handball     Hoop rolling     Horseshoes     Hula hoop     Kickball     Kick-to-kick     Lagori     Marbles[4][5]     Minkey     Mumblety-peg[8][9][a]     Musical Chairs     Paddle ball     Paper football     Punchball     Queenie[10]     Silent ball     Soccer hockey     Spinning top     Spud     Stickball     String games[5] (cat's cradle)     Stoop ball     Tennis     Tetherball     Tug of war Jumping games     Ampe, from Ghana     Double Dutch (jump rope)     Hopscotch[4][5]     Jumping Jacks     Jumping rope[4][5] (Skipping rope)     Jumpsies (also known as Chinese jump rope, elastics, or gummitwist)     Leapfrog[4][11] Memory games     Chinese whispers (Telephone[4])     Concentration     Here Comes an Old Soldier from Botany Bay (Old Soldier)     I packed my bag     Kim's Game Parlour games     Hunt the Thimble[4] (Hot and Cold)     Huckle buckle beanstalk[12] (Hot buttered beans[12])     I spy     Truth or Dare?     Wink Murder Hand games     Bloody knuckles     Chopsticks     Clapping games[4][5]         Concentration 64 (clapping, memory game)         Double Double This This         Down Down Baby         Down by the Banks     Hand games[4]     Mary Mack     Pat-a-cake     Red hands     Rock paper scissors     Thumb war Other traditional children's games     Buck buck (High Cockalorum)     Bulleribock (Sweden)     Button, button, who's got the button?     Counting out[4][5]     Crack the whip     Game of dares[13]     Floor is Lava     Follow the leader     Four corners (game)     House[14]     Hurray     Jinx     Keep Away (Monkey in the middle)     Knock, Knock, Ginger (Ding dong ditch)     Knucklebones[5] (jackstones,[4] Jacks[5])     Limbo     London Bridge     Mother May I?     Ninja     Oshikura Manju     Pencil fighting     Piljke     Pitching pennies     Poohsticks     Red Rover     Ring a Ring o' Roses     Seven Up     Simon says[14]     Singing games     Skully     Sleeping lions     Stone skipping     Tic-tac-toe     Tip-cat     Wrestling" (wikipedia.org) "About The Wee Loft Growing up in Europe, our standards are high when it comes to the beauty, uniqueness and durability of childhood toys. That’s why The Wee Loft has provided the very finest in classic and modern toys for more than 37 years.   Once a very literal “wee loft” in an old brick building in Whittier, California, today we’re blessed with two charming shops in Dana Point and Corona Del Mar. Come visit us in person or peruse our online catalog. We’re confident you’ll come away with a few new treasures and a little more childhood magic.   Our Promise   At The Wee Loft, we’re committed to the health and happiness of our children – and your children. We hand-select each item in our stores and online catalog to ensure quality and uniqueness. Our toys, like our expert staff, are dedicated to sparking happiness and creativity in our littlest friends.   Whether you’re shopping online or in one of our two beautiful stores, our staff is ready to help you select the perfect, age-appropriate item or gift. With complimentary giftwrap, birthday and holiday wish-list registry, product assembly, local home delivery and special order service, we’re committed to making childhood magical – and your life easier!" (theweeloft.com) "A set of primary colors consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printing, and paintings. Perceptions associated with a given combination of primary colors can be predicted by an appropriate mixing model (e.g., additive, subtractive) that reflects the physics of how light interacts with physical media, and ultimately the retina. Primary colors can also be conceptual (not necessarily real), either as additive mathematical elements of a color space or as irreducible phenomenological categories in domains such as psychology and philosophy. Color space primaries are precisely defined and empirically rooted in psychophysical colorimetry experiments which are foundational for understanding color vision. Primaries of some color spaces are complete (that is, all visible colors are described in terms of their primaries weighted by nonnegative primary intensity coefficients) but necessarily imaginary[1] (that is, there is no plausible way that those primary colors could be represented physically, or perceived). Phenomenological accounts of primary colors, such as the psychological primaries, have been used as the conceptual basis for practical color applications even though they are not a quantitative description in and of themselves. Sets of color space primaries are generally arbitrary, in the sense that there is no one set of primaries that can be considered the canonical set. Primary pigments or light sources are selected for a given application on the basis of subjective preferences as well as practical factors such as cost, stability, availability etc. The concept of primary colors has a long, complex history. The choice of primary colors has changed over time in different domains that study color. Descriptions of primary colors come from areas including philosophy, art history, color order systems, and scientific work involving the physics of light and perception of color. Art education materials commonly use red, yellow, and blue as primary colors, sometimes suggesting that they can mix all colors. From the perspective of modern color science, no set of real colorants or lights can mix all possible colors. ... Additive mixing of light A photograph of the red, green, and blue elements (subpixels) of an LCD. Additive mixing explains how light from these colored elements can be used for photorealistic color image reproduction. The perception elicited by multiple light sources co-stimulating the same area of the retina is additive, i.e., predicted via summing the spectral power distributions (the intensity of each wavelength) of the individual light sources assuming a color matching context.[2]: 17–22  For example, a purple spotlight on a dark background could be matched with coincident blue and red spotlights that are both dimmer than the purple spotlight. If the intensity of the purple spotlight was doubled it could be matched by doubling the intensities of both the red and blue spotlights that matched the original purple. The principles of additive color mixing are embodied in Grassmann's laws.[3] Additive mixing is sometimes described as "additive color matching"[4] to emphasize the fact the predictions based on additivity only apply assuming the color matching context. Additivity relies on assumptions of the color matching context such as the match being in the foveal field of view, under appropriate luminance, etc.[5] Additive mixing of coincident spot lights was applied in the experiments used to derive the CIE 1931 colorspace (see color space primaries section). The original monochromatic primaries of the wavelengths of 435.8 nm (violet), 546.1 nm (green), and 700 nm (red) were used in this application due to the convenience they afforded to the experimental work.[6] Small red, green, and blue elements (with controllable brightness) in electronic displays mix additively from an appropriate viewing distance to synthesize compelling colored images. This specific type of additive mixing is described as partitive mixing.[2]: 21–22  Red, green, and blue light are popular primaries for partitive mixing since primary lights with those hues provide a large triangular chromaticity gamut.[7] The exact colors chosen for additive primaries are a compromise between the available technology (including considerations such as cost and power usage) and the need for large chromaticity gamut. For example, in 1953 the NTSC specified primaries that were representative of the phosphors available in that era for color CRTs. Over decades, market pressures for brighter colors resulted in CRTs using primaries that deviated significantly from the original standard.[8] Currently, ITU-R BT.709-5 primaries are typical for high-definition television.[9] Subtractive mixing of ink layers See also: CMYK color model A magnified representation of small partially overlapping spots of cyan, magenta, yellow, and key (black) halftones in CMYK process printing. Each row represents the pattern of partially overlapping ink "rosettes" so that the patterns would be perceived as blue, green, and red when viewed on white paper from a typical viewing distance. The overlapping ink layers mix subtractively while additive mixing predicts the color appearance from the light reflected from the rosettes and white paper in between them. The subtractive color mixing model predicts the resultant spectral power distribution of light filtered through overlaid partially absorbing materials, often in the context of an underlying reflective surface such as white paper.[2]: 22–23 [10] Each layer partially absorbs some wavelengths of light from the illumination spectrum while letting others pass through, resulting in a colored appearance. The resultant spectral power distribution is predicted by sequentially taking the product of the spectral power distributions of the incoming light and transmissivity at each filter.[11] Overlapping layers of ink in printing mix subtractively over reflecting white paper, while the reflected light mixes in a partitive way to generate color images.[2]: 30–33 [12] The typical number of inks in such a printing process ranges from 3 to 6 (e.g., CMYK process, Pantone hexachrome). In general, using fewer inks as primaries results in more economical printing but using more may result in better color reproduction.[13] Cyan (C), magenta (M), and yellow (Y) are good chromatic subtractive primaries in that idealized filters with those hues can be overlaid to yield a surprisingly large chromaticity gamut.[14] A black key (K) ink (from the older "key plate") is also used in CMYK systems instead of mixing C, M and Y primaries due to both being more efficient in terms of time and expense and less likely to introduce visible defects.[15] Before the color names cyan and magenta were in common use, these primaries were often known as blue and red, respectively, and their exact color has changed over time with access to new pigments and technologies.[16] Organizations such as Fogra,[17] European Color Initiative and SWOP publish colorimetric CMYK standards for the printing industry.[18] Traditional red, yellow, and blue primary colors Color Mixing Guide, John L. King 1925, cover and plates describing yellow, red, and blue color mixing. A representation of Johannes Itten's color wheel showing his red, yellow, and blue as primary colors within the central equilateral triangle.[19] Color theorists since the seventeenth century, and many artists and designers since that time, have taken red, yellow, and blue to be the primary colors (see history below). This RYB system, in "traditional color theory", is often used to order and compare colors, and sometimes proposed as a system of mixing pigments to get a wide range of, or "all", colors.[20] O'Connor describes the role of RYB primaries in traditional color theory:[21]     A cornerstone component of traditional color theory, the RYB conceptual color model underpins the notion that the creation of an exhaustive gamut of color nuances occurs via intermixture of red, yellow, and blue pigments, especially when applied in conjunction with white and black pigment color. In the literature relating to traditional color theory and RYB color, red, yellow, and blue are often referred to as primary colors and represent exemplar hues rather than specific hues that are more pure, unique, or proprietary variants of these hues. ... Traditional color theory is based on experience with pigments, more than on the science of light. In 1920, Snow and Froehlich explained, "It does not matter to the makers of dyes if, as the physicist says, red light and green light in mixture make yellow light, when they find by experiment that red pigment and green pigment in mixture produce gray. No matter what the spectroscope may demonstrate regarding the combination of yellow rays of light and blue rays of light, the fact remains that yellow pigment mixed with the blue pigment produces green pigment. ..."[22] The widespread adoption of teaching of RYB as primary colors in post-secondary art schools in the twentieth century has been attributed to the influence of the Bauhaus, where Johannes Itten developed his ideas on color during his time there in the 1920s, and of his book on color[23][24] published in 1961.[19] In discussing color design for the web, Jason Beaird writes, "The reason many digital artists still keep a red, yellow, and blue color wheel handy is because the color schemes and concepts of traditional color theory are based on that model. ... Even though I design mostly for the Web—a medium that's displayed in RGB—I still use red, yellow, and blue as the basis for my color selection. I believe that color combinations created using the red, yellow, and blue color wheel are more aesthetically pleasing, and that good design is about aesthetics."[25] Of course, the notion that all colors can be mixed from RYB primaries is not true, just as it is not true in any system of real primaries.[26] For example, if the blue pigment is a deep Prussian blue, then a muddy desaturated green may be the best that can be had by mixing with yellow.[27] To achieve a larger gamut of colors via mixing, the blue and red pigments used in illustrative materials such as the Color Mixing Guide in the image are often closer to peacock blue (a blue-green or cyan) and carmine (color) (or crimson or magenta), respectively.[27][28][29] Printers traditionally used inks of such colors, known as "process blue" and "process red", before modern color science and the printing industry converged on the process colors (and names) cyan and magenta[27][29] (this is not to say that RYB is the same as CMY, or that it is exactly subtractive, but that there is a range of ways to conceptualize traditional RYB as a subtractive system in the framework of modern color science). Mixing pigments in limited palettes An 1896 self-portrait by Anders Zorn clearly showing a four-pigment palette of what are thought to be white, yellow ochre, vermillion, and black pigments.[30] The first known use of red, yellow, and blue as "simple" or "primary" colors, by Chalcidius, ca. AD 300, was possibly based on the art of paint mixing.[31] Mixing pigments for the purpose of creating realistic paintings with diverse color gamuts is known to have been practiced at least since Ancient Greece (see history section). The identity of a/the set of minimal pigments to mix diverse gamuts has long been the subject of speculation by theorists whose claims have changed over time, for example Pliny's white, black, one or another red, and "sil", which might have been yellow or blue; Robert Boyle's white, black, red, yellow, and blue; and variations with more or fewer "primary" color or pigments. Some writers and artists have found these schemes difficult to reconcile with the actual practice of painting.[32]: 29–38  Nonetheless, it has long been known that limited palettes consisting of a small set of pigments are sufficient to mix a diverse gamut of colors.[33][34][35][36][37] The set of pigments available to mix diverse gamuts of color (in various media such as oil, watercolor, acrylic, gouache, and pastel) is large and has changed throughout history.[38][39] There is no consensus on a specific set of pigments that are considered primary colors – the choice of pigments depends entirely on the artist's subjective preference of subject and style of art as well as material considerations like lightfastness and mixing behavior.[40] A variety of limited palettes have been employed by artists for their work.[41][42] The color of light (i.e., the spectral power distribution) reflected from illuminated surfaces coated in paint mixes is not well approximated by a subtractive or additive mixing model.[43] Color predictions that incorporate light scattering effects of pigment particles and paint layer thickness require approaches based on the Kubelka–Munk equations[44] but even such approaches are not expected to predict the color of paint mixtures precisely due to inherent limitations.[45] Artists typically rely on mixing experience and "recipes"[46][47] to mix desired colors from a small initial set of primaries and do not use mathematical modeling. MacEvoy explains why artists often chose a palette closer to RYB than to CMY: "Because the 'optimal' pigments in practice produce unsatisfactory mixtures; because the alternative selections are less granulating, more transparent, and mix darker values; and because visual preferences have demanded relatively saturated yellow to red mixtures, obtained at the expense of relatively dull green and purple mixtures. Artists jettisoned 'theory' to obtain the best color mixtures in practice."[48] Color space primaries A conceptual visualization of a color matching experiment. A circular foveal bipartite field (about the size one's thumbnail an arm's length away[49]) is presented to the observer in a dark surround. One part of the field is illuminated by a monochromatic test stimulus. The participant adjusts the intensities of the three coincident monochromatic primary lights (which are usually red, green and blue hues) on either field until both the test stimulus and match stimulus appear as the exact same color. In this case the participant has added red to the 480 nm test stimulus and has almost matched the match stimulus made of only the green and blue lights of comparable intensities. The specific monochromatic primaries shown here are from the Stiles-Burch 1955 experiment.[50] The CIE RGB,[51][52] CIE XYZ[53] color matching functions and LMS cone fundamentals.[54][55] The curves are all for 2° fields. Color space primaries are derived from canonical colorimetric experiments that represent a standardized model of an observer (i.e., a set of color matching functions) adopted by Commission Internationale de l'Eclairage (CIE) standards. The abbreviated account of color space primaries in this section is based on descriptions in Colorimetry - Understanding The CIE System.[56] The CIE 1931 standard observer is derived experiments in which participants observing a foveal 2° bipartite field with a dark surround. Half of the field is illuminated with a monochromatic test stimulus (ranging from 380 nm to 780 nm) and the other half is the matching stimulus illuminated with three coincident monochromatic primary lights: 700 nm for red (R), 546.1 nm for green (G), and 435.8 nm for blue (B).[56]: 29  These primaries correspond to CIE RGB color space. The intensities of the primary lights could be adjusted by the participant observer until the matching stimulus matched the test stimulus, as predicted by Grassman's laws of additive mixing. Different standard observers from other color matching experiments have been derived since 1931. The variations in experiments include choices of primary lights, field of view, number of participants etc.[57] but the presentation below is representative of those results. Matching was performed across many participants in incremental steps along the range of test stimulus wavelengths (380 nm to 780 nm) to ultimately yield the color matching functions: r ¯ ( λ ) {\displaystyle {\overline {r}}(\lambda )} {\overline {r}}(\lambda ), g ¯ ( λ ) {\displaystyle {\overline {g}}(\lambda )} {\overline {g}}(\lambda ) and b ¯ ( λ ) {\displaystyle {\overline {b}}(\lambda )} {\overline {b}}(\lambda ) that represent the relative intensities of red, green, and blue light to match each wavelength ( λ {\displaystyle \lambda } \lambda ). These functions imply that [ C ] {\displaystyle [C]} [C] units of the test stimulus with any spectral power distribution, P ( λ ) {\displaystyle P(\lambda )} P(\lambda), can be matched by [R], [G], and [B] units of each primary where:[56]: 28      Eq. 1 [ C ] = ∫ 380 n m 780 n m r ¯ ( λ ) P ( λ ) d λ ⋅ [ R ] + ∫ 380 n m 780 n m g ¯ ( λ ) P ( λ ) d λ ⋅ [ G ] + ∫ 380 n m 780 n m b ¯ ( λ ) P ( λ ) d λ ⋅ [ B ] {\displaystyle [C]=\int _{380\,nm}^{780\,nm}{\overline {r}}(\lambda )P(\lambda )d\lambda \cdot [R]+\int _{380\,nm}^{780\,nm}{\overline {g}}(\lambda )P(\lambda )d\lambda \cdot [G]+\int _{380\,nm}^{780\,nm}{\overline {b}}(\lambda )P(\lambda )d\lambda \cdot [B]} {\displaystyle [C]=\int _{380\,nm}^{780\,nm}{\overline {r}}(\lambda )P(\lambda )d\lambda \cdot [R]+\int _{380\,nm}^{780\,nm}{\overline {g}}(\lambda )P(\lambda )d\lambda \cdot [G]+\int _{380\,nm}^{780\,nm}{\overline {b}}(\lambda )P(\lambda )d\lambda \cdot [B]} Each integral term in the above equation is known as a tristimulus value and measures amounts in the adopted units. No set of real primary lights can match another monochromatic light under additive mixing so at least one of the color matching functions is negative for each wavelength. A negative tristimulus value corresponds to that primary being added to the test stimulus instead of the matching stimulus to achieve a match. The negative tristimulus values made certain types of calculations difficult, so the CIE put forth new color matching functions x ¯ ( λ ) {\displaystyle {\overline {x}}(\lambda )} {\overline {x}}(\lambda ), y ¯ ( λ ) {\displaystyle {\overline {y}}(\lambda )} {\overline {y}}(\lambda ), and z ¯ ( λ ) {\displaystyle {\overline {z}}(\lambda )} {\overline {z}}(\lambda ) defined by the following linear transformation:[56]: 30      Eq. 2 [ x ¯ ( λ ) y ¯ ( λ ) z ¯ ( λ ) ] = [ 2.768892 1.751748 1.130160 1.000000 4.590700 0.060100 0 0.056508 5.594292 ] [ r ¯ ( λ ) g ¯ ( λ ) b ¯ ( λ ) ] {\displaystyle {\begin{bmatrix}{\overline {x}}(\lambda )\\{\overline {y}}(\lambda )\\{\overline {z}}(\lambda )\end{bmatrix}}={\begin{bmatrix}2.768892&1.751748&1.130160\\1.000000&4.590700&0.060100\\0&0.056508&5.594292\\\end{bmatrix}}{\begin{bmatrix}{\overline {r}}(\lambda )\\{\overline {g}}(\lambda )\\{\overline {b}}(\lambda )\end{bmatrix}}} {\displaystyle {\begin{bmatrix}{\overline {x}}(\lambda )\\{\overline {y}}(\lambda )\\{\overline {z}}(\lambda )\end{bmatrix}}={\begin{bmatrix}2.768892&1.751748&1.130160\\1.000000&4.590700&0.060100\\0&0.056508&5.594292\\\end{bmatrix}}{\begin{bmatrix}{\overline {r}}(\lambda )\\{\overline {g}}(\lambda )\\{\overline {b}}(\lambda )\end{bmatrix}}} These new color matching functions correspond to imaginary primary lights X, Y, and Z (CIE XYZ color space). All colors can be matched by finding the amounts [X], [Y], and [Z] analogously to [R], [G], and [B] as defined in Eq. 1. The functions x ¯ ( λ ) {\displaystyle {\overline {x}}(\lambda )} {\overline {x}}(\lambda ), y ¯ ( λ ) {\displaystyle {\overline {y}}(\lambda )} {\overline {y}}(\lambda ), and z ¯ ( λ ) {\displaystyle {\overline {z}}(\lambda )} {\overline {z}}(\lambda ) based on the specifications that they should be nonnegative for all wavelengths, y ¯ ( λ ) {\displaystyle {\overline {y}}(\lambda )} {\overline {y}}(\lambda ) be equal to photometric luminance, and that [ X ] = [ Y ] = [ Z ] {\displaystyle [X]=[Y]=[Z]} {\displaystyle [X]=[Y]=[Z]} for an equienergy (i.e., a uniform spectral power distribution) test stimulus.[56]: 30  Derivations use the color matching functions, along with data from other experiments, to ultimately yield the cone fundamentals: l ¯ ( λ ) {\displaystyle {\overline {l}}(\lambda )} {\displaystyle {\overline {l}}(\lambda )}, m ¯ ( λ ) {\displaystyle {\overline {m}}(\lambda )} {\displaystyle {\overline {m}}(\lambda )} and s ¯ ( λ ) {\displaystyle {\overline {s}}(\lambda )} {\displaystyle {\overline {s}}(\lambda )}. These functions correspond to the response curves for the three types of color photoreceptors found in the human retina: long-wavelength (L), medium-wavelength (M), and short-wavelength (S) cones. The three cone fundamentals are related to the original color matching functions by the following linear transformation (specific to a 10° field):[56]: 227      Eq. 3 [ l ¯ ( λ ) m ¯ ( λ ) s ¯ ( λ ) ] = [ 0.192325269 0.749548882 0.0675726702 0.0192290085 0.949098496 0.113830196 0 0.0105107859 0.991427669 ] [ r ¯ ( λ ) g ¯ ( λ ) b ¯ ( λ ) ] {\displaystyle {\begin{bmatrix}{\overline {l}}(\lambda )\\{\overline {m}}(\lambda )\\{\overline {s}}(\lambda )\end{bmatrix}}={\begin{bmatrix}0.192325269&0.749548882&0.0675726702\\0.0192290085&0.949098496&0.113830196\\0&0.0105107859&0.991427669\\\end{bmatrix}}{\begin{bmatrix}{\overline {r}}(\lambda )\\{\overline {g}}(\lambda )\\{\overline {b}}(\lambda )\end{bmatrix}}} {\displaystyle {\begin{bmatrix}{\overline {l}}(\lambda )\\{\overline {m}}(\lambda )\\{\overline {s}}(\lambda )\end{bmatrix}}={\begin{bmatrix}0.192325269&0.749548882&0.0675726702\\0.0192290085&0.949098496&0.113830196\\0&0.0105107859&0.991427669\\\end{bmatrix}}{\begin{bmatrix}{\overline {r}}(\lambda )\\{\overline {g}}(\lambda )\\{\overline {b}}(\lambda )\end{bmatrix}}} The L, M, and S primaries correspond to imaginary lights that stimulate only the L, M, and S cones respectively. These primaries are the basis for LMS color space, which has significant physiological relevance as these three photoreceptors mediate trichromatic color vision in humans. The R, G, and, B primaries as described here are real in that they represent physical lights but incomplete since some colors cannot be matched with primary intensity coefficients that are all nonnegative. The X, Y, Z and the L, M, S primaries are imaginary, since none can be represented by real lights or colorants, and complete since all colors can be defined in terms of primary intensity coefficients that are all nonnegative. Other color spaces such as sRGB[58] and scRGB[59] are partially defined in terms of linear transformations from CIE XYZ which have their own specific primaries. The choice of which color space to use is essentially arbitrary and depends on the utility to a specific application.[1] The color-matching context is always three dimensional (as seen in all the previously described color spaces) but more general color appearance models like CIECAM02 describe color in more dimensions[60] and can be used to predict how colors appear under different viewing conditions. Humans are normally trichromats and use three (or more) primaries for color reproduction applications requiring a diverse gamuts.[61] Some humans are monochromats or dichromats, corresponding to specific forms of color blindness in which color vision is mediated by only one or two of the types of color receptors. Participants with color blindness in color matching experiments were essential in the determination of cone fundamentals.[62] There is one scholarly report of a functional human tetrachromat.[63] Most other mammals are dichromats[64] while birds and many fish are tetrachromats.[65] Psychological primaries Ewald Hering's illustration[66] of the psychological primaries. Red/green and yellow/blue form opponent pairs (top). Each color can be psychologically mixed to make other colors (bottom) with both members of the other pair but not with its opponent according to Hering. Main article: Opponent process The opponent process was proposed by Ewald Hering in which he described the four "simple" or "primary" colors (einfache or grundfarben) as red, green, yellow and blue.[67] To Hering, colors appeared either as these pure colors or as "psychological mixes" of two of them. Furthermore, these colors were organized in "opponent" pairs, red vs. green and yellow vs. blue so that mixing could occur across pairs (e.g., a yellowish green or a yellowish red) but not within a pair (i.e., greenish red cannot be imagined). An achromatic opponent process along black and white is also part of Hering's explanation of color perception. Hering asserted that we did not know why these color relationships were true but knew that they were.[68] Red, green, yellow, and blue (sometimes with white and black[69]) are known as the psychological primaries. Although there is a great deal of evidence for the opponent process in the form of neural mechanisms,[70] there is currently no clear mapping of the psychological primaries to neural substrates.[71] The psychological primaries were applied by Richard S. Hunter as the primaries for Hunter L,a,b colorspace that led to the creation of CIELAB.[72] The Natural Color System is also directly inspired by the psychological primaries.[73] History Philosophy Philosophical writing from ancient Greece has described notions of primary colors but they can be difficult to interpret in terms of modern color science. Theophrastus (ca. 371–287 BCE) described Democritus’ position that the primary colors were white, black, red, and green.[74]: 4  In Classical Greece, Empedocles identified white, black, red, and, (depending on the interpretation) either yellow or green as primary colors.[74]: 8  Aristotle described a notion in which white and black could be mixed in different ratios to yield chromatic colors;[74]: 12  this idea had considerable influence in Western thinking about color. François d'Aguilon's notion of the five primary colors (white, yellow, red, blue, black) was influenced by Aristotle's idea of the chromatic colors being made of black and white.[74]: 87 The 20th century philosopher Ludwig Wittgenstein explored color-related ideas using red, green, blue, and yellow as primary colors.[75] [76] The color scheme of François d'Aguilon, where the two simple colors of white (albus) and black (niger) are mixed to the "noble" colors of yellow (flavus), red (rubeus), and blue (caeruleus). Orange (aureus), purple (purpureus), and green (viridis) are each combinations of two noble colors.[77] Light and color vision Isaac Newton used the term "primary color" to describe the colored spectral components of sunlight.[78][79] A number of color theorists did not agree with Newton's work, David Brewster advocated that red, yellow, and blue light could be combined into any spectral hue late into the 1840s.[80][81] Thomas Young proposed red, green, and violet as the three primary colors, while James Clerk Maxwell favored changing violet to blue.[82] Hermann von Helmholtz proposed "a slightly purplish red, a vegetation-green, slightly yellowish, and an ultramarine-blue" as a trio.[83] Newton, Young, Maxwell, and Helmholtz were all prominent contributors to "modern color science"[84]: 1–39  that ultimately described the perception of color in terms of the three types of retinal photoreceptors. Colorants John Gage's The Fortunes Of Apelles provides a summary of the history of primary colors[32] as pigments in painting and describes the evolution of the idea as complex. Gage begins by describing Pliny The Elder's account of notable Greek painters who used four primaries.[85] Pliny distinguished the pigments (i.e., substances) from their apparent colors: white from Milos (ex albis), red from Sinope (ex rubris), Attic yellow (sil) and atramentum (ex nigris). Sil was historically confused as a blue pigment between the 16th and 17th centuries leading to claims about white, black, red, and blue being the fewest colors required for painting. Thomas Bardwell, an 18th century Norwich portrait painter, was skeptical of practical relevance of Pliny's account.[86] Robert Boyle, the Irish chemist, introduced the term primary color in English in 1664 and claimed that there were five primary colors (white, black, red, yellow, and blue).[33][87] The German painter Joachim von Sandrart eventually proposed removing white and black from the primaries and that one only needed red, yellow, blue, and green to paint "the whole creation".[32]: 36  Partial list of authors describing red, yellow, and blue as the (chromatic) primary colors before 18th century (adapted from Shamey and Kuehni)[74]: 108  Year     Author     Color terms     Descriptive term Ca. 325     Chalcidius     Pallidus, rubeus, cyaneus     Generic colors Ca. 1266     Roger Bacon     Glaucus, rubeus, viriditas     Principal species Ca. 1609     Anselmus de Boodt     Flavus, ruber, caeruleus     Principal colors Ca. 1613     François d'Aguilon     Flavus, rubeus, caeruleus     Simple colors Ca. 1664     Robert Boyle     Yellow, red, blue     Simple, primary Ca. 1680     André Félibien     Jaune, rouge, bleu     Principal, primitive Red, yellow, and blue as primaries became a popular notion in the 18th and 19th centuries. Jacob Christoph Le Blon, an engraver, was the first to use separate plates for each color in mezzotint printmaking: yellow, red, and blue, plus black to add shades and contrast. Le Blon used primitive in 1725 to describe red, yellow, and blue in a very similar sense as Boyle used primary.[84]: 6  Moses Harris, an entomologist and engraver, also describes red, yellow, and blue as "primitive" colors in 1766.[88] Léonor Mérimée described red, yellow, and blue in his book on painting (originally published in French in 1830) as the three simple/primitive colors that can make a "great variety" of tones and colors found in nature.[89] George Field, a chemist, used the word primary to describe red, yellow, and blue in 1835.[90] Michel Eugène Chevreul, also a chemist, discussed red, yellow, and blue as "primary" colors in 1839.[91] [92] Color order systems Johann Heinrich Lambert's "Farbenpyramide" tetrahedron published in 1772. Gamboge (yellow), carmine (red), and Prussian blue pigments are used the corner swatches of each "level" of lightness with mixtures filling the others and white at the top.[93] Philipp Otto Runge's sketch showing bl (blue), g (yellow) and r (red) as the fundamental colors.[94] Historical perspectives[74][95] on color order systems[96] ("catalogs" of color) that were proposed in the 18th and 19th centuries describe them as using red, yellow and blue pigments as chromatic primaries. Tobias Mayer (a German mathematician, physicist, and astronomer) described a triangular bipyramid with red, yellow and blue at the 3 vertices in the same plane, white at the top vertex and black and the bottom vertex in a public lecture in 1758.[74]: 115  There are 11 planes of colors between the white and black vertices inside the triangular bipyramid. Mayer did not seem to distinguish between colored light and colorant though he used vermilion, orpiment (King’s yellow), and Bergblau (azurite) in partially complete colorings of planes in his solid.[97]: 79  Johann Heinrich Lambert (a Swiss mathematician, physicist, and astronomer) proposed a triangular pyramid with gamboge, carmine, and Prussian blue as primaries and only white at the top vertex (since Lambert could produce a mixture that was sufficiently black with those pigments).[74]: 123  Lambert's work on this system was published in 1772.[98] Philipp Otto Runge (the Romantic German painter) firmly believed in the theory of red, yellow and blue as the primary colors[97]: 87  (again without distinguishing light color and colorant). His color sphere was ultimately described in an essay titled Farben-Kugel[97] (color ball) published by Goethe in 1810.[97]: 84  His spherical model of colors equally spaced red, yellow and blue longitudinally with orange, green and violet in between them and white and black at opposite poles.[97]: 85  Red, yellow, and blue as primary colors Numerous authors teach that red, yellow, and blue (RYB) are the primary colors, in art education materials since at least the 19th century, following the ideas tabulated above from earlier centuries.[99][100][101] A wide variety of contemporary educational sources also describe the RYB primaries. These sources range from children's books,[102] art material manufacturers[103] to painting[104] and color guides.[105] Art education materials often suggest that RYB primaries can be mixed to create all other colors.[106][107] Criticism Albert Munsell, an American painter (and creator of the Munsell color system), referred to the notion RYB primaries as "mischief", "a widely accepted error", and underspecified in his book A Color Notation, first published in 1905.[108] Itten's ideas about RYB primaries have been criticized[109] as ignoring modern color science[74]: 282  with demonstrations that some of Itten's claims about mixing RYB primaries are impossible." (wikipedia.org) "A secondary color is a color made by mixing of two primary colors in a given color space.... Additive secondaries Main article: Additive color Light (RGB) Main article: RGB color model For the human eye, good primary colors of light are red, green, and blue. Combining lights of these colors produces a large range of visible colors.                green     (●)     +     red     (●)     =     yellow     (●) red     (●)     +     blue     (●)     =     magenta     (●) blue     (●)     +     green     (●)     =     cyan     (●)   That is, the primary and secondary RGB colors (with secondary colors in boldface) are:   green       yellow       red       magenta       blue       cyan Combining RGB colors means adding light (thus the term "additive color"), and the combinations are brighter. When all three primaries are combined in equal amounts, the result is white. The RGB secondary colors produced by the addition of light turn out to be good primary colors for pigments, the mixing of which subtracts light. Subtractive secondaries Main article: Subtractive color Pigments, such as inks and paint, display color by absorbing some wavelengths of light and reflecting the remainder. When pigments are combined, they absorb the combination of their colors, and reflect less. Thus, combining pigments results in a darker color. This is called subtractive color-mixing, as mixing pigments subtracts wavelengths from the light that is reflected. Printing (CMYK) Main article: CMYK color model The mixture of equal amounts of these colors produce the secondary colors red, blue, and "lime" green (the RGB primary colors of light), as follows:                yellow     (●)     +     magenta     (●)     =     red     (●) magenta     (●)     +     cyan     (●)     =     blue     (●) cyan     (●)     +     yellow     (●)     =     green     (●)   That is, the primary and secondary CMY colors (with secondary colors in boldface) are:   yellow       red       magenta       blue       cyan       green       yellow Ideally, combining three perfect primary colors in equal amounts would produce black, but this is impossible to achieve in practice. Therefore a "key" pigment, usually black, is added to printing to produce dark shades more efficiently. This combination is referred to as CMYK, where K stands for Key. Traditional painting (RYB) Main article: RYB color model Before the discovery of CMY, at least as far back as Goethe, the best primary colors were thought to be red, yellow, and blue. Mixing these pigments in equal amounts produces orange, green, and purple:[1]                yellow     (●)     +     red     (●)     =     orange     (●) red     (●)     +     blue     (●)     =     purple     (●) blue     (●)     +     yellow     (●)     =     green     (●)   That is, the primary and secondary RYB colors (with secondary colors in boldface) are:[2]   yellow       orange       red       purple       blue       green       yellow" (wikipedia.org) "In the visual arts, color theory is a body of practical guidance to color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, secondary color, and tertiary color. Understanding color theory dates to antiquity. Aristotle (d. 322 BCE) and Claudius Ptolemy (d. 168 CE) already discussed which and how colors can be produced by mixing other colors. The influence of light on color was investigated and revealed further by al-Kindi (d. 873) and Ibn al-Haytham (d.1039). Ibn Sina (d. 1037), Nasir al-Din al-Tusi (d. 1274) and Robert Grosseteste (d. 1253) discovered that contrary to the teachings of Aristotle, there are multiple color paths to get from black to white[1]. [2] More modern approaches to color theory principles can be found in the writings of Leone Battista Alberti (c. 1435) and the notebooks of Leonardo da Vinci (c. 1490). A formalization of "color theory" began in the 18th century, initially within a partisan controversy over Isaac Newton's theory of color (Opticks, 1704) and the nature of primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.[citation needed] The application of color theory ranges from ancient Egyptian uses to modern commercial advertising. Colors affect our mood and perception. In ancient civilizations, color was explored for its healing properties. Phototherapy (light therapy) was practiced in ancient Egypt, Greece, China and India. The Egyptians utilized sunlight as well as color for healing.[3] Color has been investigated for its healing potential since 2000 BC.... Classifications Color can be classified according to     Warm and Cold     Receding and Advancing     Positive and negative     Subtractive and additive Color abstractions Additive color mixing (such as in a computer) Subtractive color mixing (such as in a printer) The foundations of pre-20th-century color theory were built around "pure" or ideal colors, characterized by different sensory experiences rather than attributes of the physical world. This has led to a number of inaccuracies in traditional color theory principles that are not always remedied in modern formulations.[5] Another issue has been the tendency to describe color effects holistically or categorically, for example as a contrast between "yellow" and "blue" conceived as generic colors, when most color effects are due to contrasts on three relative attributes which define all colors:     Value (light vs. dark, or white vs. black),     Chroma [saturation, purity, strength, intensity] (intense vs. dull), and     Hue (e.g. the name of the color family: red, yellow, green, cyan, blue, magenta). The visual impact of "yellow" vs. "blue" hues in visual design depends on the relative lightness and saturation of the hues. These confusions are partly historical and arose in scientific uncertainty about the color perception that was not resolved until the late 19th-century when the artistic notions were already entrenched. They also arise from the attempt to describe the highly contextual and flexible behavior of color perception in terms of abstract color sensations that can be generated equivalently by any visual media. Many historical "color theorists" have assumed that three "pure" primary colors can mix into all possible colors, and any failure of specific paints or inks to match this ideal performance is due to the impurity or imperfection of the colorants. In reality, only imaginary "primary colors" used in colorimetry can "mix" or quantify all visible (perceptually possible) colors; but to do this, these imaginary primaries are defined as lying outside the range of visible colors; i.e., they cannot be seen. Any three real "primary" colors of light, paint or ink can mix only a limited range of colors, called a gamut, which is always smaller (contains fewer colors) than the full range of colors humans can perceive.[6] Historical background Color theory was originally formulated in terms of three "primary" or "primitive" colors—red, yellow and blue (RYB)—because these colors were believed capable of mixing all other colors.[7] Goethe's color wheel from his 1810 Theory of Colours The RYB primary colors became the foundation of 18th-century theories of color vision,[citation needed] as the fundamental sensory qualities that are blended in the perception of all physical colors, and conversely, in the physical mixture of pigments or dyes. These theories were enhanced by 18th-century investigations of a variety of purely psychological color effects, in particular the contrast between "complementary" or opposing hues that are produced by color afterimages and in the contrasting shadows in colored light. These ideas and many personal color observations were summarized in two founding documents in color theory: the Theory of Colours (1810) by the German poet Johann Wolfgang von Goethe, and The Law of Simultaneous Color Contrast (1839) by the French industrial chemist Michel Eugène Chevreul. Charles Hayter published A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information (London 1826), in which he described how all colors could be obtained from just three. Page from 1826 A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information by Charles Hayter Subsequently, German and English scientists established in the late 19th century that color perception is best described in terms of a different set of primary colors—red, green and blue-violet (RGB)—modeled through the additive mixture of three monochromatic lights. Subsequent research anchored these primary colors in the differing responses to light by three types of color receptors or cones in the retina (trichromacy). On this basis the quantitative description of the color mixture or colorimetry developed in the early 20th century, along with a series of increasingly sophisticated models of color space and color perception, such as the opponent process theory. Across the same period, industrial chemistry radically expanded the color range of lightfast synthetic pigments, allowing for substantially improved saturation in color mixtures of dyes, paints, and inks. It also created the dyes and chemical processes necessary for color photography. As a result, three-color printing became aesthetically and economically feasible in mass printed media, and the artists' color theory was adapted to primary colors most effective in inks or photographic dyes: cyan, magenta, and yellow (CMY). (In printing, dark colors are supplemented by black ink, known as the CMYK system; in both printing and photography, white is provided by the color of the paper.) These CMY primary colors were reconciled with the RGB primaries, and subtractive color mixing with additive color mixing, by defining the CMY primaries as substances that absorbed only one of the retinal primary colors: cyan absorbs only red (−R+G+B), magenta only green (+R−G+B), and yellow only blue-violet (+R+G−B). It is important to add that the CMYK, or process, color printing is meant as an economical way of producing a wide range of colors for printing, but is deficient in reproducing certain colors, notably orange and slightly deficient in reproducing purples. A wider range of colors can be obtained with the addition of other colors to the printing process, such as in Pantone's Hexachrome printing ink system (six colors), among others. Munsell's 1905 color system represented as a three-dimensional solid showing all three color making attributes: lightness, saturation and hue. For much of the 19th-century artistic color theory either lagged behind scientific understanding or was augmented by science books written for the lay public, in particular Modern Chromatics (1879) by the American physicist Ogden Rood, and early color atlases developed by Albert Munsell (Munsell Book of Color, 1915, see Munsell color system) and Wilhelm Ostwald (Color Atlas, 1919). Major advances were made in the early 20th century by artists teaching or associated with the German Bauhaus, in particular Wassily Kandinsky, Johannes Itten, Faber Birren and Josef Albers, whose writings mix speculation with an empirical or demonstration-based study of color design principles. Traditional color theory Complementary colors Chevreul's 1855 "chromatic diagram" based on the RYB color model, showing complementary colors and other relationships Main article: Complementary colors For the mixing of colored light, Isaac Newton's color wheel is often used to describe complementary colors, which are colors that cancel each other's hue to produce an achromatic (white, gray or black) light mixture. Newton offered as a conjecture that colors exactly opposite one another on the hue circle cancel out each other's hue; this concept was demonstrated more thoroughly in the 19th century. An example of complementary colors would be red and green[8] A key assumption in Newton's hue circle was that the "fiery" or maximum saturated hues are located on the outer circumference of the circle, while achromatic white is at the center. Then the saturation of the mixture of two spectral hues was predicted by the straight line between them; the mixture of three colors was predicted by the "center of gravity" or centroid of three triangle points, and so on. Primary, secondary, and tertiary colors of the RYB color model According to traditional color theory based on subtractive primary colors and the RYB color model, yellow mixed with purple, orange mixed with blue, or red mixed with green produces an equivalent gray and are the painter's complementary colors. These contrasts form the basis of Chevreul's law of color contrast: colors that appear together will be altered as if mixed with the complementary color of the other color. A piece of yellow fabric placed on a blue background will appear tinted orange because orange is the complementary color to blue. However, when complementary colors are chosen based on the definition by light mixture, they are not the same as the artists' primary colors. This discrepancy becomes important when color theory is applied across media. Digital color management uses a hue circle defined according to additive primary colors (the RGB color model), as the colors in a computer monitor are additive mixtures of light, not subtractive mixtures of paints. One reason the artist's primary colors work at all is due to the imperfect pigments being used have sloped absorption curves, and change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish color. This works much better with oil colors than it does with watercolors and dyes. The old primaries depend on sloped absorption curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the spectrum. Another reason the correct primary colors were not used by early artists is they were not available as durable pigments. Modern methods in chemistry were needed to produce them. Warm vs. cool colors The distinction between "warm" and "cool" colors has been important since at least the late 18th century.[9] The difference (as traced by etymologies in the Oxford English Dictionary), seems related to the observed contrast in landscape light, between the "warm" colors associated with daylight or sunset, and the "cool" colors associated with a gray or overcast day. Warm colors are often said to be hues from red through yellow, browns, and tans included; cool colors are often said to be the hues from blue-green through blue violet, most grays included. There is a historical disagreement about the colors that anchor the polarity, but 19th-century sources put the peak contrast between red-orange and greenish-blue. Color theory has described perceptual and psychological effects to this contrast. Warm colors are said to advance or appear more active in a painting, while cool colors tend to recede; used in interior design or fashion, warm colors are said to arouse or stimulate the viewer, while cool colors calm and relax.[10] Most of these effects, to the extent they are real, can be attributed to the higher saturation and lighter value of warm pigments in contrast to cool pigments; brown is a dark, unsaturated warm color that few people think of as visually active or psychologically arousing. The traditional warm/cool association of a color is reversed relative to the color temperature of a theoretical radiating black body; the hottest stars radiate blue (cool) light, and the coolest radiate red (warm) light. The hottest radiating bodies (e.g. stars) have a "cool" color, while the less hot bodies radiate with a "warm" color. (image is in Kelvin scale) Doppler redshift for receding and blueshift for advancing This contrast is further seen in the psychological associations of colors with the Doppler effect seen in astronomical objects. Traditional psychological associations, where warm colors are associated with advancing objects and cool colors with receding objects, are directly opposite those seen in astrophysics, where stars or galaxies moving towards our viewpoint on Earth are blueshifted (advancing) and stars or galaxies moving away from Earth are redshifted (receding). Achromatic colors Any color that lacks strong chromatic content is said to be unsaturated, achromatic, near-neutral, or neutral. Near neutrals include browns, tans, pastels, and darker colors. Near neutrals can be of any hue or lightness. Pure achromatic, or neutral colors include black, white and all grays. Near neutrals are obtained by mixing pure colors with white, black or grey, or by mixing two complementary colors. In color theory, neutral colors are easily modified by adjacent more saturated colors and they appear to take on the hue complementary to the saturated color; e.g., next to a bright red couch, a gray wall will appear distinctly greenish, This is a property of human vision. Black and white have long been known to combine "well" with almost any other colors; black decreases the apparent saturation or brightness of colors paired with it and white shows off all hues to equal effect.[citation needed] Tints and shades Main article: Tints and shades When mixing colored light (additive color models), the achromatic mixture of spectrally balanced red, green, and blue (RGB) is always white, not gray or black. When we mix colorants, such as the pigments in paint mixtures, a color is produced which is always darker and lower in chroma, or saturation, than the parent colors. This moves the mixed color toward a neutral color—a gray or near-black. Lights are made brighter or dimmer by adjusting their brightness, or energy level; in painting, lightness is adjusted through mixture with white, black, or a color's complement. It is common among some painters to darken a paint color by adding black paint—producing colors called shades—or lighten a color by adding white—producing colors called tints. However, it is not always the best way for representational painting, as an unfortunate result is for colors to also shift in hue. For instance, darkening a color by adding black can cause colors such as yellows, reds, and oranges, to shift toward the greenish or bluish part of the spectrum. Lightening a color by adding white can cause a shift towards blue when mixed with reds and oranges. Another practice when darkening a color is to use its opposite, or complementary, color (e.g. purplish-red added to yellowish-green) in order to neutralize it without a shift in hue, and darken it if the additive color is darker than the parent color. When lightening a color this hue shift can be corrected with the addition of a small amount of an adjacent color to bring the hue of the mixture back in line with the parent color (e.g. adding a small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum). Split primary colors In painting and other visual arts, two-dimensional color wheels or three-dimensional color solids are used as tools to teach beginners the essential relationships between colors. The organization of colors in a particular color model depends on the purpose of that model: some models show relationships based on human color perception, whereas others are based on the color mixing properties of a particular medium such as a computer display or set of paints. This system is still popular among contemporary painters,[citation needed] as it is basically a simplified version of Newton's geometrical rule that colors closer together on the hue circle will produce more vibrant mixtures. However, with the range of contemporary paints available, many artists simply add more paints to their palette as desired for a variety of practical reasons. For example, they may add a scarlet, purple and/or green paint to expand the mixable gamut; and they include one or more dark colors (especially "earth" colors such as yellow ochre or burnt sienna) simply because they are convenient to have premixed.[citation needed] Printers commonly augment a CMYK palette with spot (trademark specific) ink colors. Color harmony It has been suggested that "Colors seen together to produce a pleasing affective response are said to be in harmony".[11] However, color harmony is a complex notion because human responses to color are both affective and cognitive, involving emotional response and judgment. Hence, our responses to color and the notion of color harmony is open to the influence of a range of different factors. These factors include individual differences (such as age, gender, personal preference, affective state, etc.) as well as cultural, sub-cultural, and socially-based differences which gives rise to conditioning and learned responses about color. In addition, context always has an influence on responses about color and the notion of color harmony, and this concept is also influenced by temporal factors (such as changing trends) and perceptual factors (such as simultaneous contrast) which may impinge on human response to color. The following conceptual model illustrates this 21st-century approach to color harmony:     Color harmony = f ( Col ⁡ 1 , 2 , 3 , … , n ) ⋅ ( I D + C E + C X + P + T ) {\displaystyle {\text{Color harmony}}=f(\operatorname {Col} 1,2,3,\dots ,n)\cdot (ID+CE+CX+P+T)} {\displaystyle {\text{Color harmony}}=f(\operatorname {Col} 1,2,3,\dots ,n)\cdot (ID+CE+CX+P+T)} wherein color harmony is a function (f) of the interaction between color/s (Col 1, 2, 3, …, n) and the factors that influence positive aesthetic response to color: individual differences (ID) such as age, gender, personality and affective state; cultural experiences (CE), the prevailing context (CX) which includes setting and ambient lighting; intervening perceptual effects (P) and the effects of time (T) in terms of prevailing social trends.[12] Georg Christoph Lichtenberg. Göttingen, 1775, plate III. In addition, given that humans can perceive over 2.8 million different colors,[13] it has been suggested that the number of possible color combinations is virtually infinite thereby implying that predictive color harmony formulae are fundamentally unsound.[14] Despite this, many color theorists have devised formulae, principles or guidelines for color combination with the aim being to predict or specify positive aesthetic response or "color harmony". Color wheel models have often been used as a basis for color combination principles or guidelines and for defining relationships between colors. Some theorists and artists believe juxtapositions of complementary color will produce strong contrast, a sense of visual tension as well as "color harmony"; while others believe juxtapositions of analogous colors will elicit a positive aesthetic response. Color combination guidelines (or formulas) suggest that colors next to each other on the color wheel model (analogous colors) tend to produce a single-hued or monochromatic color experience and some theorists also refer to these as "simple harmonies".[15] In addition, split complementary color schemes usually depict a modified complementary pair, with instead of the "true" second color being chosen, a range of analogous hues around it are chosen, i.e. the split complements of red are blue-green and yellow-green. A triadic color scheme adopts any three colors approximately equidistant around a color wheel model. Feisner and Mahnke are among a number of authors who provide color combination guidelines in greater detail.[16][17] Ignaz Schiffermüller, Versuch eines Farbensystems (Vienna, 1772), plate I. Color combination formulae and principles may provide some guidance but have limited practical application. This is due to the influence of contextual, perceptual, and temporal factors which will influence how color/s are perceived in any given situation, setting, or context. Such formulae and principles may be useful in fashion, interior and graphic design, but much depends on the tastes, lifestyle, and cultural norms of the viewer or consumer. As early as the ancient Greek philosophers, many theorists have devised color associations and linked particular connotative meanings to specific colors.[18] However, connotative color associations and color symbolism tends to be culture-bound and may also vary across different contexts and circumstances. For example, red has many different connotative and symbolic meanings from exciting, arousing, sensual, romantic, and feminine; to a symbol of good luck; and also acts as a signal of danger. Such color associations tend to be learned and do not necessarily hold irrespective of individual and cultural differences or contextual, temporal or perceptual factors.[19] It is important to note that while color symbolism and color associations exist, their existence does not provide evidential support for color psychology or claims that color has therapeutic properties.[20] Monochromatic The monochromatic formula chooses only one color (or hue). Variations of the color are created by changing the value and saturation of the color. Since only one hue is used, the color and its variations are guaranteed to work. Current status Color theory has not developed an explicit explanation of how specific media affect color appearance: colors have always been defined in the abstract, and whether the colors were inks or paints, oils or watercolors, transparencies or reflecting prints, computer displays or movie theaters, was not considered especially relevant.[21] Josef Albers investigated the effects of relative contrast and color saturation on the illusion of transparency, but this is an exception to the rule." (wikipedia.org) "In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions are much larger than the wavelengths of the photons in question), the photons can be said to follow Snell's Law. Translucency (also called translucence or translucidity) allows light to pass through, but does not necessarily (again, on the macroscopic scale) follow Snell's law; the photons can be scattered at either of the two interfaces, or internally, where there is a change in index of refraction. In other words, a translucent material is made up of components with different indices of refraction. A transparent material is made up of components with a uniform index of refraction.[1] Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. The opposite property of translucency is opacity. When light encounters a material, it can interact with it in several different ways. These interactions depend on the wavelength of the light and the nature of the material. Photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as plate glass and clean water, transmit much of the light that falls on them and reflect little of it; such materials are called optically transparent. Many liquids and aqueous solutions are highly transparent. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque. Many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of white light frequencies. They absorb certain portions of the visible spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation. This is what gives rise to color. The attenuation of light of all frequencies and wavelengths is due to the combined mechanisms of absorption and scattering.[2] Transparency can provide almost perfect camouflage for animals able to achieve it. This is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent. ... Etymology     late Middle English: from Old French, from medieval Latin transparent- ‘shining through’, from Latin transparere, from trans- ‘through’ + parere ‘be visible’.[citation needed]     late 16th century (in the Latin sense): from Latin translucent- ‘shining through’, from the verb translucere, from trans- ‘through’ + lucere ‘to shine’.[citation needed]     late Middle English opake, from Latin opacus ‘darkened’. The current spelling (rare before the 19th century) has been influenced by the French form.[citation needed] Introduction     This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2021) (Learn how and when to remove this template message) With regard to the absorption of light, primary material considerations include:     At the electronic level, absorption in the ultraviolet and visible (UV-Vis) portions of the spectrum depends on whether the electron orbitals are spaced (or "quantized") such that they can absorb a quantum of light (or photon) of a specific frequency, and does not violate selection rules. For example, in most glasses, electrons have no available energy levels above them in range of that associated with visible light, or if they do, they violate selection rules, meaning there is no appreciable absorption in pure (undoped) glasses, making them ideal transparent materials for windows in buildings.     At the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the length scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include:     Crystalline structure: whether the atoms or molecules exhibit the 'long-range order' evidenced in crystalline solids.     Glassy structure: scattering centers include fluctuations in density or composition.     Microstructure: scattering centers include internal surfaces such as grain boundaries, crystallographic defects and microscopic pores.     Organic materials: scattering centers include fiber and cell structures and boundaries. Main article: Light scattering General mechanism of diffuse reflection Diffuse reflection - Generally, when light strikes the surface of a (non-metallic and non-glassy) solid material, it bounces off in all directions due to multiple reflections by the microscopic irregularities inside the material (e.g., the grain boundaries of a polycrystalline material, or the cell or fiber boundaries of an organic material), and by its surface, if it is rough. Diffuse reflection is typically characterized by omni-directional reflection angles. Most of the objects visible to the naked eye are identified via diffuse reflection. Another term commonly used for this type of reflection is "light scattering". Light scattering from the surfaces of objects is our primary mechanism of physical observation.[3][4] Light scattering in liquids and solids depends on the wavelength of the light being scattered. Limits to spatial scales of visibility (using white light) therefore arise, depending on the frequency of the light wave and the physical dimension (or spatial scale) of the scattering center. Visible light has a wavelength scale on the order of a half a micrometer. Scattering centers (or particles) as small as one micrometer have been observed directly in the light microscope (e.g., Brownian motion).[5][6] Transparent ceramics Optical transparency in polycrystalline materials is limited by the amount of light which is scattered by their microstructural features. Light scattering depends on the wavelength of the light. Limits to spatial scales of visibility (using white light) therefore arise, depending on the frequency of the light wave and the physical dimension of the scattering center. For example, since visible light has a wavelength scale on the order of a micrometer, scattering centers will have dimensions on a similar spatial scale. Primary scattering centers in polycrystalline materials include microstructural defects such as pores and grain boundaries. In addition to pores, most of the interfaces in a typical metal or ceramic object are in the form of grain boundaries which separate tiny regions of crystalline order. When the size of the scattering center (or grain boundary) is reduced below the size of the wavelength of the light being scattered, the scattering no longer occurs to any significant extent. In the formation of polycrystalline materials (metals and ceramics) the size of the crystalline grains is determined largely by the size of the crystalline particles present in the raw material during formation (or pressing) of the object. Moreover, the size of the grain boundaries scales directly with particle size. Thus a reduction of the original particle size well below the wavelength of visible light (about 1/15 of the light wavelength or roughly 600/15 = 40 nanometers) eliminates much of light scattering, resulting in a translucent or even transparent material. Computer modeling of light transmission through translucent ceramic alumina has shown that microscopic pores trapped near grain boundaries act as primary scattering centers. The volume fraction of porosity had to be reduced below 1% for high-quality optical transmission (99.99 percent of theoretical density). This goal has been readily accomplished and amply demonstrated in laboratories and research facilities worldwide using the emerging chemical processing methods encompassed by the methods of sol-gel chemistry and nanotechnology.[7] Translucency of a material being used to highlight the structure of a photographic subject Transparent ceramics have created interest in their applications for high energy lasers, transparent armor windows, nose cones for heat seeking missiles, radiation detectors for non-destructive testing, high energy physics, space exploration, security and medical imaging applications. Large laser elements made from transparent ceramics can be produced at a relatively low cost. These components are free of internal stress or intrinsic birefringence, and allow relatively large doping levels or optimized custom-designed doping profiles. This makes ceramic laser elements particularly important for high-energy lasers. The development of transparent panel products will have other potential advanced applications including high strength, impact-resistant materials that can be used for domestic windows and skylights. Perhaps more important is that walls and other applications will have improved overall strength, especially for high-shear conditions found in high seismic and wind exposures. If the expected improvements in mechanical properties bear out, the traditional limits seen on glazing areas in today's building codes could quickly become outdated if the window area actually contributes to the shear resistance of the wall. Currently available infrared transparent materials typically exhibit a trade-off between optical performance, mechanical strength and price. For example, sapphire (crystalline alumina) is very strong, but it is expensive and lacks full transparency throughout the 3–5 micrometer mid-infrared range. Yttria is fully transparent from 3–5 micrometers, but lacks sufficient strength, hardness, and thermal shock resistance for high-performance aerospace applications. Not surprisingly, a combination of these two materials in the form of the yttrium aluminium garnet (YAG) is one of the top performers in the field. Absorption of light in solids     This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2021) (Learn how and when to remove this template message) When light strikes an object, it usually has not just a single frequency (or wavelength) but many. Objects have a tendency to selectively absorb, reflect or transmit light of certain frequencies. That is, one object might reflect green light while absorbing all other frequencies of visible light. Another object might selectively transmit blue light while absorbing all other frequencies of visible light. The manner in which visible light interacts with an object is dependent upon the frequency of the light, the nature of the atoms in the object, and often the nature of the electrons in the atoms of the object. Some materials allow much of the light that falls on them to be transmitted through the material without being reflected. Materials that allow the transmission of light waves through them are called optically transparent. Chemically pure (undoped) window glass and clean river or spring water are prime examples of this. Materials which do not allow the transmission of any light wave frequencies are called opaque. Such substances may have a chemical composition which includes what are referred to as absorption centers. Most materials are composed of materials which are selective in their absorption of light frequencies. Thus they absorb only certain portions of the visible spectrum. The frequencies of the spectrum which are not absorbed are either reflected back or transmitted for our physical observation. In the visible portion of the spectrum, this is what gives rise to color.[8][9] Absorption centers are largely responsible for the appearance of specific wavelengths of visible light all around us. Moving from longer (0.7 micrometer) to shorter (0.4 micrometer) wavelengths: red, orange, yellow, green and blue (ROYGB) can all be identified by our senses in the appearance of color by the selective absorption of specific light wave frequencies (or wavelengths). Mechanisms of selective light wave absorption include:     Electronic: Transitions in electron energy levels within the atom (e.g., pigments). These transitions are typically in the ultraviolet (UV) and/or visible portions of the spectrum.     Vibrational: Resonance in atomic/molecular vibrational modes. These transitions are typically in the infrared portion of the spectrum. UV-Vis: Electronic transitions In electronic absorption, the frequency of the incoming light wave is at or near the energy levels of the electrons within the atoms which compose the substance. In this case, the electrons will absorb the energy of the light wave and increase their energy state, often moving outward from the nucleus of the atom into an outer shell or orbital. The atoms that bind together to make the molecules of any particular substance contain a number of electrons (given by the atomic number Z in the periodic chart). Recall that all light waves are electromagnetic in origin. Thus they are affected strongly when coming into contact with negatively charged electrons in matter. When photons (individual packets of light energy) come in contact with the valence electrons of atom, one of several things can and will occur:     A molecule absorbs the photon, some of the energy may be lost via luminescence, fluorescence and phosphorescence.     A molecule absorbs the photon which results in reflection or scattering.     A molecule cannot absorb the energy of the photon and the photon continues on its path. This results in transmission (provided no other absorption mechanisms are active). Most of the time, it is a combination of the above that happens to the light that hits an object. The states in different materials vary in the range of energy that they can absorb. Most glasses, for example, block ultraviolet (UV) light. What happens is the electrons in the glass absorb the energy of the photons in the UV range while ignoring the weaker energy of photons in the visible light spectrum. But there are also existing special glass types, like special types of borosilicate glass or quartz that are UV-permeable and thus allow a high transmission of ultra violet light. Thus, when a material is illuminated, individual photons of light can make the valence electrons of an atom transition to a higher electronic energy level. The photon is destroyed in the process and the absorbed radiant energy is transformed to electric potential energy. Several things can happen then to the absorbed energy: it may be re-emitted by the electron as radiant energy (in this case the overall effect is in fact a scattering of light), dissipated to the rest of the material (i.e. transformed into heat), or the electron can be freed from the atom (as in the photoelectric and Compton effects). Infrared: Bond stretching Normal modes of vibration in a crystalline solid The primary physical mechanism for storing mechanical energy of motion in condensed matter is through heat, or thermal energy. Thermal energy manifests itself as energy of motion. Thus, heat is motion at the atomic and molecular levels. The primary mode of motion in crystalline substances is vibration. Any given atom will vibrate around some mean or average position within a crystalline structure, surrounded by its nearest neighbors. This vibration in two dimensions is equivalent to the oscillation of a clock’s pendulum. It swings back and forth symmetrically about some mean or average (vertical) position. Atomic and molecular vibrational frequencies may average on the order of 1012 cycles per second (Terahertz radiation). When a light wave of a given frequency strikes a material with particles having the same or (resonant) vibrational frequencies, then those particles will absorb the energy of the light wave and transform it into thermal energy of vibrational motion. Since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies (or portions of the spectrum) of infrared light. Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural resonant frequencies of vibration of the objects. When infrared light of these frequencies strikes an object, the energy is reflected or transmitted. If the object is transparent, then the light waves are passed on to neighboring atoms through the bulk of the material and re-emitted on the opposite side of the object. Such frequencies of light waves are said to be transmitted.[10][11] Transparency in insulators An object may be not transparent either because it reflects the incoming light or because it absorbs the incoming light. Almost all solids reflect a part and absorb a part of the incoming light. When light falls onto a block of metal, it encounters atoms that are tightly packed in a regular lattice and a "sea of electrons" moving randomly between the atoms.[12] In metals, most of these are non-bonding electrons (or free electrons) as opposed to the bonding electrons typically found in covalently bonded or ionically bonded non-metallic (insulating) solids. In a metallic bond, any potential bonding electrons can easily be lost by the atoms in a crystalline structure. The effect of this delocalization is simply to exaggerate the effect of the "sea of electrons". As a result of these electrons, most of the incoming light in metals is reflected back, which is why we see a shiny metal surface. Most insulators (or dielectric materials) are held together by ionic bonds. Thus, these materials do not have free conduction electrons, and the bonding electrons reflect only a small fraction of the incident wave. The remaining frequencies (or wavelengths) are free to propagate (or be transmitted). This class of materials includes all ceramics and glasses. If a dielectric material does not include light-absorbent additive molecules (pigments, dyes, colorants), it is usually transparent to the spectrum of visible light. Color centers (or dye molecules, or "dopants") in a dielectric absorb a portion of the incoming light. The remaining frequencies (or wavelengths) are free to be reflected or transmitted. This is how colored glass is produced. Most liquids and aqueous solutions are highly transparent. For example, water, cooking oil, rubbing alcohol, air, and natural gas are all clear. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are chiefly responsible for their excellent optical transmission. The ability of liquids to "heal" internal defects via viscous flow is one of the reasons why some fibrous materials (e.g., paper or fabric) increase their apparent transparency when wetted. The liquid fills up numerous voids making the material more structurally homogeneous.[citation needed] Light scattering in an ideal defect-free crystalline (non-metallic) solid which provides no scattering centers for incoming light will be due primarily to any effects of anharmonicity within the ordered lattice. Light transmission will be highly directional due to the typical anisotropy of crystalline substances, which includes their symmetry group and Bravais lattice. For example, the seven different crystalline forms of quartz silica (silicon dioxide, SiO2) are all clear, transparent materials.[13] Optical waveguides Propagation of light through a multi-mode optical fiber A laser beam bouncing down an acrylic rod, illustrating the total internal reflection of light in a multimode optical fiber Optically transparent materials focus on the response of a material to incoming light waves of a range of wavelengths. Guided light wave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions to act as a transmission medium for a range of frequencies simultaneously (multi-mode optical fiber) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation is relatively lossless.[citation needed] An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis by the process of total internal reflection. The fiber consists of a core surrounded by a cladding layer. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The refractive index is the parameter reflecting the speed of light in a material. (Refractive index is the ratio of the speed of light in vacuum to the speed of light in a given medium. The refractive index of vacuum is therefore 1.) The larger the refractive index, the more slowly light travels in that medium. Typical values for core and cladding of an optical fiber are 1.48 and 1.46, respectively.[citation needed] When light traveling in a dense medium hits a boundary at a steep angle, the light will be completely reflected. This effect, called total internal reflection, is used in optical fibers to confine light in the core. Light travels along the fiber bouncing back and forth off of the boundary. Because the light must strike the boundary with an angle greater than the critical angle, only light that enters the fiber within a certain range of angles will be propagated. This range of angles is called the acceptance cone of the fiber. The size of this acceptance cone is a function of the refractive index difference between the fiber's core and cladding. Optical waveguides are used as components in integrated optical circuits (e.g. combined with lasers or light-emitting diodes, LEDs) or as the transmission medium in local and long haul optical communication systems.[citation needed] Mechanisms of attenuation See also: Light scattering Light attenuation by ZBLAN and silica fibers Attenuation in fiber optics, also known as transmission loss, is the reduction in intensity of the light beam (or signal) with respect to distance traveled through a transmission medium. Attenuation coefficients in fiber optics usually use units of dB/km through the medium due to the very high quality of transparency of modern optical transmission media. The medium is usually a fiber of silica glass that confines the incident light beam to the inside. Attenuation is an important factor limiting the transmission of a signal across large distances. In optical fibers the main attenuation source is scattering from molecular level irregularities (Rayleigh scattering)[14] due to structural disorder and compositional fluctuations of the glass structure. This same phenomenon is seen as one of the limiting factors in the transparency of infrared missile domes[citation needed]. Further attenuation is caused by light absorbed by residual materials, such as metals or water ions, within the fiber core and inner cladding. Light leakage due to bending, splices, connectors, or other outside forces are other factors resulting in attenuation.[15][16] As camouflage Many animals of the open sea, like this Aurelia labiata jellyfish, are largely transparent. Further information: List of camouflage methods Many marine animals that float near the surface are highly transparent, giving them almost perfect camouflage.[17] However, transparency is difficult for bodies made of materials that have different refractive indices from seawater. Some marine animals such as jellyfish have gelatinous bodies, composed mainly of water; their thick mesogloea is acellular and highly transparent. This conveniently makes them buoyant, but it also makes them large for their muscle mass, so they cannot swim fast, making this form of camouflage a costly trade-off with mobility.[17] Gelatinous planktonic animals are between 50 and 90 percent transparent. A transparency of 50 percent is enough to make an animal invisible to a predator such as cod at a depth of 650 metres (2,130 ft); better transparency is required for invisibility in shallower water, where the light is brighter and predators can see better. For example, a cod can see prey that are 98 percent transparent in optimal lighting in shallow water. Therefore, sufficient transparency for camouflage is more easily achieved in deeper waters.[17] For the same reason, transparency in air is even harder to achieve, but a partial example is found in the glass frogs of the South American rain forest, which have translucent skin and pale greenish limbs.[18] Several Central American species of clearwing (ithomiine) butterflies and many dragonflies and allied insects also have wings which are mostly transparent, a form of crypsis that provides some protection from predators." (wikipedia.org) "Connect Four (also known as Four Up, Plot Four, Find Four, Captain's Mistress, Four in a Row, Drop Four, and Gravitrips in the Soviet Union) is a two-player connection board game, in which the players choose a color and then take turns dropping colored tokens into a seven-column, six-row vertically suspended grid. The pieces fall straight down, occupying the lowest available space within the column. The objective of the game is to be the first to form a horizontal, vertical, or diagonal line of four of one's own tokens. Connect Four is a solved game. The first player can always win by playing the right moves. The game was first sold under the Connect Four trademark[3] by Milton Bradley in February 1974. ... Gameplay Gameplay of Connect Four     Object: Connect four of your checkers in a row while preventing your opponent from doing the same. But, look out – your opponent can sneak up on you and win the game!     — Milton Bradley, Connect Four "Pretty Sneaky, Sis" television commercial, 1977[4] A gameplay example (right), shows the first player starting Connect Four by dropping one of their yellow discs into the center column of an empty game board. The two players then alternate turns dropping one of their discs at a time into an unfilled column, until the second player, with red discs, achieves a diagonal four in a row, and wins the game. If the board fills up before either player achieves four in a row, then the game is a draw. Mathematical solution Connect Four is a two-player game with perfect information for both sides, meaning that nothing is hidden from anyone. Connect Four also belongs to the classification of an adversarial, zero-sum game, since a player's advantage is an opponent's disadvantage. One measure of complexity of the Connect Four game is the number of possible games board positions. For classic Connect Four played on a 7-column-wide, 6-row-high grid, there are 4,531,985,219,092 positions[5] for all game boards populated with 0 to 42 pieces. The game was first solved by James Dow Allen (October 1, 1988), and independently by Victor Allis (October 16, 1988).[6] Allis describes a knowledge-based approach,[7] with nine strategies, as a solution for Connect Four. Allen also describes winning strategies[8][9] in his analysis of the game. At the time of the initial solutions for Connect Four, brute-force analysis was not deemed feasible given the game's complexity and the computer technology available at the time. Connect Four has since been solved with brute-force methods, beginning with John Tromp's work in compiling an 8-ply database[6][10] (February 4, 1995). The artificial intelligence algorithms able to strongly solve Connect Four are minimax or negamax, with optimizations that include alpha-beta pruning, move ordering, and transposition tables. The code for solving Connect Four with these methods is also the basis for the Fhourstones[11] integer performance benchmark. The solved conclusion for Connect Four is first-player-win. With perfect play, the first player can force a win,[6][7][8] on or before the 41st move[12] by starting in the middle column. The game is a theoretical draw when the first player starts in the columns adjacent to the center. For the edges of the game board, column 1 and 2 on left (or column 7 and 6 on right), the exact move-value score for first player start is loss on the 40th move,[12] and loss on the 42nd move,[12] respectively. In other words, by starting with the four outer columns, the first player allows the second player to force a win. Rule variations There are many variations of Connect Four with differing game board sizes, game pieces, and gameplay rules. Many variations are popular with game theory and artificial intelligence research, rather than with physical game boards and gameplay by persons. The most commonly-used Connect Four board size is 7 columns × 6 rows. Size variations include 5×4, 6×5, 8×7, 9×7, 10×7, 8×8, Infinite Connect-Four,[13] and Cylinder-Infinite Connect-Four.[14] A travel version of the Milton Bradley game. Several versions of Hasbro's Connect Four physical gameboard make it easy to remove game pieces from the bottom one at a time. Along with traditional gameplay, this feature allows for variations of the game.[15] Some earlier game versions also included specially-marked discs, and cardboard column extenders, for additional variations to the game.[16] PopOut "PopOut" redirects here. For other uses, see Pop Out (disambiguation). PopOut starts the same as traditional gameplay, with an empty board and players alternating turns placing their own colored discs into the board. During each turn, a player can either add another disc from the top, or if one has any discs of their own color on the bottom row, remove (or "pop out") a disc of one's own color from the bottom. Popping a disc out from the bottom drops every disc above it down one space, changing their relationship with the rest of the board and changing the possibilities for a connection. The first player to connect four of their discs horizontally, vertically, or diagonally wins the game. Pop 10 Before play begins, Pop 10 is set up differently from the traditional game. Taking turns, each player places one of their own color discs into the slots filling up only the bottom row, then moving on to the next row until it is filled, and so forth until all rows have been filled. Gameplay works by players taking turns removing a disc of one's own color through the bottom of the board. If the disc that was removed was part of a four-disc connection at the time of its removal, the player sets it aside out of play and immediately takes another turn. If it was not part of a "connect four", then it must be placed back on the board through a slot at the top into any open space in an alternate column (whenever possible) and the turn ends, switching to the other player. The first player to set aside ten discs of their color wins the game. Five-in-a-Row The Five-in-a-Row variation for Connect Four is a game played on a 6 high, 9 wide grid. Two additional board columns, already filled with player pieces in an alternating pattern, are added to the left and right sides of the standard 6-by-7 game board. The game plays similarly to the original Connect Four, except players must now get five pieces in a row to win. This is still a 42-ply game since the two new columns added to the game represent twelve game pieces already played, before the start of a game. Power Up In this variation of Connect Four, players begin a game with one or more specially-marked "Power Checkers" game pieces, which each player may choose to play once per game. When playing a piece marked with an anvil icon, for example, the player may immediately pop out all pieces below it, leaving the anvil piece at the bottom row of the game board. Other marked game pieces include one with a wall icon, allowing a player to play a second consecutive non-winning turn with an unmarked piece; a "×2" icon, allowing for an unrestricted second turn with an unmarked piece; and a bomb icon, allowing a player to immediately pop out an opponent's piece. Other versions     This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Connect Four" – news · newspapers · books · scholar · JSTOR (June 2019) (Learn how and when to remove this template message) Hasbro also produces various sizes of Giant Connect Four, suitable for outdoor use. The largest is built from weather-resistant wood, and measures 120 cm in both width and height. Connect Four was released for the Microvision video game console in 1979, developed by Robert Hoffberg. It was also released for the Texas Instruments 99/4 computer the same year. With the proliferation of mobile devices, Connect Four has regained popularity as a game that can be played quickly and against another person over an Internet connection. In 2007, Milton Bradley published Connect Four Stackers. Instead of the usual grid, the game features a board to place colored discs on. Just like standard Connect Four, the object of the game is to try get four in a row of a specific color of discs.[17] In 2008, another board variation Hasbro published as a physical game is Connect 4x4.[18] This game features a two-layer vertical grid with colored discs for four players, plus blocking discs. The object of the game is also to get four in a row for a specific color of discs. A SpongeBob SquarePants version of the game was released in 2009 for the show's 10th anniversary. The rules are the same as the normal version; the chips have the faces of SpongeBob and Patrick on them. It was re-released in 2014, but with Patrick being replaced with Plankton. In 2013, Bay Tek Games released a Connect Four ticket redemption arcade game under license from Hasbro. There are standard and deluxe versions of the game. Two players move and drop the checkers using buttons. If only one player is playing, the player plays against the computer. Both the player that wins and the player that loses get tickets. The player that wins gets to play a bonus round where a checker is moving and the player needs to press the button at the right time to get the ticket jackpot. In 2015 Winning Moves published Connect Four Twist & Turn. This game variant features a game tower instead of the flat game grid. The tower has five rings that twist independently. Gameplay is similar to standard Connect Four where players try to get four in a row of their own colored discs. However, with Twist & Turn, players have the choice to twist a ring after they have played a piece. It adds a subtle layer of strategy to the gameplay.[according to whom?] In 2018, Bay Tek Games released their second Connect Four arcade game, Connect 4 Hoops. Players throw basketballs into basketball hoops, and they show up as checkers on the video screen. The game can be played by two players, or by one player against the computer. Both the player that wins and the player that loses get tickets. In 2018, Hasbro released Connect 4 Shots. This version requires the players to bounce coloured balls into the grid until one player achieves four in a row. Popular culture     Broadcaster and writer Stuart Maconie—while working at the NME—started a rumour that Connect Four was invented by David Bowie, which became an urban myth.[19]     On The Hub's game show Family Game Night, there is a game under the name "Connect 4 Basketball" in which teams use colored balls.     Nintendo added a version of this game called "Four-in-a-row" to their tabletop games compilation named Clubhouse Games: 51 Worldwide Classics for the Nintendo Switch.[20]     In the video game A Way Out, Vincent and Leo can play Connect Four as a minigame." (wikipedia.org) "A connection game is a type of abstract strategy game in which players attempt to complete a specific type of connection with their pieces. This could involve forming a path between two or more endpoints, completing a closed loop, or connecting all of one's pieces so they are adjacent to each other.[1] Connection games typically have simple rules, but complex strategies. They have minimal components and may be played as board games, computer games, or even paper-and-pencil games. In many connection games, the goal is to connect two opposite sides of the board. In these games, players take turns placing or moving pieces until one side has a continuous line of pieces connecting the two sides of the playing area. Hex, TwixT, and PÜNCT are typical examples of this type of game. ... Popular connection games Examples of the three winning structures in Havannah, on a base-8 board. From left to right, they are the fork, the ring and the bridge. Havannah Main article: Havannah Havannah is a two-player abstract strategy board game invented by Christian Freeling. Unlike Hex or other connection games, Havannah has three conditions that enable a player to win: creating a Fork; creating a Bridge; or creating a Ring. A ring is a loop around one or more cells regardless of whether or not the encircled cells are occupied by any player or empty. A bridge connects any two of the six corner cells of the board. A fork connects any three edges of the board (a corner point is not considered part of an edge). Havannah has "a sophisticated and varied strategy" and is best played on a base-10 hexagonal board, 10 hex cells to a side.[2] The game was published for a period in Germany by Ravensburger, with a smaller, base-8 board suitable for beginners. It is nowadays only produced by Hexboards.[3] Hex Main article: Hex (board game) 11×11 Hex gameboard showing a winning configuration for Blue Hex is a two player abstract strategy board game in which players attempt to connect opposite sides of a hexagonal board. Hex was invented by mathematician and poet Piet Hein in 1942 and independently by John Nash in 1948. It is traditionally played on an 11×11 rhombus board, although 13×13 and 19×19 boards are also popular. Each player is assigned a pair of opposite sides of the board which they must try to connect by taking turns placing a stone of their color onto any empty space. Once placed, the stones cannot be moved or removed. A player wins when they successfully connect their sides together through a chain of adjacent stones. Draws are impossible in Hex due to the topology of the game board. The game has deep strategy, sharp tactics and a profound mathematical underpinning related to the Brouwer fixed-point theorem. The game was first marketed as a board game in Denmark under the name Con-tac-tix, and Parker Brothers marketed a version of it in 1952 called Hex; they are no longer in production. Hex can also be played with paper and pencil on hexagonally ruled graph paper. Tak Main article: Tak (game) Tak being played with a "Tavern" set Tak is a two-player abstract strategy game designed by James Ernest and Patrick Rothfuss and published by Cheapass Games in 2016. Its design was based around the fictional game of Tak described in Patrick Rothfuss' 2011 fantasy novel The Wise Man's Fear.[4] The goal of Tak is to be the first to connect two opposite edges of the board with your pieces, called "stones", and create a road. To accomplish this, players take turns placing their own stones and building their road while blocking and capturing their opponent's pieces to hinder their efforts at the same. A player "captures" a stone by stacking one of their pieces on top of the opponent's. This creates a three dimensional element to the game play absent in other well known connection games, such as hex. In addition the player may place and move a piece called the capstone or play normal stones "standing" up on their edge. The capstone and standing stones have different powers and rules regarding their use in the game. The Game of Y Main article: Y (game) A commercially-sold Y board Y is an abstract strategy board game, first described by John Milnor in the early 1950s.[5][6][7] The goal of Y is similar to Hex except that each player has the identical goal of making a connection between all three sides forming a "Y" rather than "owning" specific sides that must be connected. The game was independently invented in 1953 by Craige Schensted and Charles Titus. It is an early member in a long line of games Schensted has developed, each game more complex but also more generalized." (wikipedia.org)
  • Condition: New
  • Gender: Boys & Girls
  • Country/Region of Manufacture: Germany
  • Min. Number of Players: 2 players
  • Game Type: Educational Game
  • Theme: Colors
  • Year: 1996
  • Game Title: Mix N Match
  • MPN: 24 365 5
  • Brand: Ravensburger
  • Recommended Age Range: Ages 4-8

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