en>Brirush at 20:38, 29 November 2014

2014-11-29T20:38:55Z

en>Phantomsteve: Cleaned up using AutoEd; formatting: heading-style, whitespace (using Advisor.js)

2013-03-03T16:09:10Z

Cleaned up using AutoEd; formatting: heading-style, whitespace (using Advisor.js)

← Older revision		Revision as of 18:09, 3 March 2013
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	~~Hi there!~~ :~~) My name~~ is ~~Kelli~~, ~~I'm~~ a ~~student studying Agriculture~~ and ~~Life Sciences~~ from ~~Maastricht~~, ~~Netherlands~~.<br><br>~~Also visit my web~~-~~site~~; [http://~~juegosdecarros4x4~~.~~net~~/~~profile~~/~~anmlnr~~.html ~~wordpress dropbox backup~~]		[[File:Lichtenberg color triangle Tobias Mayer 1775.jpg\|thumb\|right\|200px\|A 1775 color triangle by [[Tobias Mayer]].]]
			[[File:CIExy1931 srgb gamut.png\|right\|thumb\|200px\|The [[sRGB]] color triangle, shown as a subset of ''x,y'' space, a [[chromaticity]] space based on [[CIE 1931]] colorimetry]]

			A '''color triangle''' is an arrangement of [[color]]s within a [[triangle]], based on the [[Additive color\|additive]] combination of three [[primary color]]s at its corners.

			An additive [[color space]] defined by three primary colors has a [[chromaticity]] [[gamut]] that is a color triangle, when the amounts of the primaries are constrained to be nonnegative.<ref>{{cite book \| title = Digital Pictures: Representation, Compression, and Standards \| author = Arun N. Netravali \| coauthors = G. Haskell \| authorlink = Arun Netravali \| edition = second \| publisher = Springer \| year = 1995 \| isbn = 0-306-42195-X \| url = http://books.google.com/?id=-TXYfZrCBuQC&pg=PA101&dq=gamut+color-triangle }}</ref><ref>{{cite book \| title = Color Vision: Perspectives from Different Disciplines \| author = Werner Backhaus, Reinhold Kliegl and John Simon Werner \| publisher = Walter de Gruyter \| year = 1998 \| isbn = 3-11-015431-5 \| url = http://books.google.com/?id=DrduOSrOFegC&pg=PA58&dq=positive+color-triangle }}</ref>

			Before the theory of additive color was proposed by [[Thomas Young (scientist) \|Thomas Young]] and further developed by [[James Clerk Maxwell]] and [[Hermann von Helmholtz]], triangles were also used to organize colors, for example around a system of [[RYB color model\|red, yellow, and blue primary colors]].<ref>{{cite book \| title = The Creation of Color in Eighteenth-Century Europe \| author = Sarah Lowengard \| publisher = Columbia University Press \| year = 2008 \| url = http://www.gutenberg-e.org/lowengard/A_Chap03.html \| isbn = 0-231-12454-6 }}</ref>

			After the development of the [[CIE 1931 color space\|CIE system]], color triangles were used as chromaticity diagrams, including briefly with the [[trilinear coordinates]] representing the chromaticity values.<ref>{{cite journal\|title=A Maxwell Triangle Yielding Uniform Chromaticity Scales\|journal=[[JOSA]]\|first=Deane B.\|last=Judd\|volume=25\|issue=1\|date=January 1935\|pages=24–35\| url=http://www.opticsinfobase.org/abstract.cfm?URI=josa-25-1-24\|doi=10.1364/JOSA.25.000024}}</ref> Since the sum of the three chromaticity values has a fixed value, it suffices to depict only two of the three values, using Cartesian co-ordinates. In the modern ''x,y'' diagram, the large triangle bounded by the imaginary primaries X, Y, and Z has corners (1,0), (0,1), and (0,0), respectively; color triangles with real primaries are often shown within this space.

			==Maxwell's disc==
			Maxwell was intrigued by [[James David Forbes]]'s use of color [[top]]s. By rapidly spinning the top, Forbes created the illusion of a single color that was a mixture of the primaries:<ref>{{cite book\|title=The Natural Philosophy of James Clerk Maxwell\|author=Peter Michael Harman\|publisher=[[Cambridge University Press]]\|isbn=0-521-00585-X\|year=1998\| url=http://books.google.com/?id=qf6jtc4nZisC&pg=PA41&lpg=PA41&dq=forbes+maxwell+color+top}}</ref>

			{{quote\|[The] experiments of Professor J. D. Forbes, which I witnessed in 1849… [established] that blue and yellow do not make green, but a pinkish tint, when neither prevails in the combination…[and the] result of mixing yellow and blue was, I believe, not previously known.\|James Clerk Maxwell\|Experiments on colour, as perceived by the eye, with remarks on colour-blindness (1855), [[Transactions of the Royal Society of Edinburgh]]}}

			Maxwell took this a step further by using a circular scale around the rim with which to measure the ratios of the primaries, choosing [[vermilion]] (V), [[emerald (color)\|emerald]] (EG), and [[ultramarine]] (U).<ref>{{cite book\|title=The Scientific Papers of James Clerk Maxwell\|author=James Clerk Maxwell\|publisher=[[Dover Publications]]\|isbn=0-486-49560-4\|year=2003\| url=http://books.google.com/?id=duyKrTNps_AC&pg=PA127&lpg=PA127&dq=maxwell+vermilion+emerald+ultramarine}}</ref>

			Initially, he compared the color he observed on the spinning top with a paper of different color, in order to find a match. Later, he mounted a pair of papers, snow white (SW) and [[ivory black]] (Bk), in an inner circle, thereby creating shades of gray. By adjusting the ratio of primaries, he matched the observed gray of the inner wheel, for example:<ref name=maxwell>James Clerk Maxwell (1855), [http://www.jimworthey.com/archive/index.html Experiments on colour as perceived by the eye, with remarks on colour-blindness]</ref>

			<math>0.37V+0.27U+0.36EG=0.28SW+0.72BK</math>

			To determine the chromaticity of an arbitrary color, he replaced one of the primaries with a sample of the test color and adjusted the ratios until he found a match. For [[pale chrome]] (PC) he found <math>0.33PC+0.55U+0.12EG=0.37SW+0.63BK</math>. Next, he rearranged the equation to express the test color (PC, in this example) in terms of the primaries.

			This would be the precursor to the [[CIE 1931 color space#Color matching functions\|color matching functions]] of the [[CIE 1931 color space]], whose chromaticity diagram is shown above.

			<gallery>
			Image:Color top 1895.png\|Drawing of Maxwell's color top
			Image:YoungJamesClerkMaxwell.jpg\|[[ James Clerk Maxwell\|Maxwell]] with his wheel
			Image:Maxwell color Triangle Luckiesh 1921.png\|Maxwell's color triangle
			Image:Fick color triangle.png\|<small>A color triangle attributed to Fick in 1892, based on imaginary primaries corresponding to the three primary sensations of the human eye. In such a triangle, all real colors fall within the curved outline defined by the "pure sensations".</small>
			</gallery>

			==See also==
			* [[Color wheel]]

			==References==
			{{reflist}}

			{{Color space}}

			[[Category:James Clerk Maxwell]]

en>JForget: Reverted edits by 121.97.176.98 (talk) to last version by Bgeelhoed

2008-02-09T23:41:26Z

Reverted edits by 121.97.176.98 (talk) to last version by Bgeelhoed

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Hi there! :) My name is Kelli, I'm a student studying Agriculture and Life Sciences from Maastricht, Netherlands.<br><br>Also visit my web-site; [http://juegosdecarros4x4.net/profile/anmlnr.html wordpress dropbox backup]

Sampling design - Revision history

en>Brirush at 20:38, 29 November 2014

en>Phantomsteve: Cleaned up using AutoEd; formatting: heading-style, whitespace (using Advisor.js)

en>JForget: Reverted edits by 121.97.176.98 (talk) to last version by Bgeelhoed