Editing Yellow (section)

=== Optics, color printing, and computer screens ===
{{infobox color
|title=Process Yellow (subtractive primary)
|hex=FFEF00
|source=[https://web.archive.org/web/20120626160106/http://www.tintbook.com/] [[CMYK]]
|isccname=Vivid greenish yellow
}}

<gallery mode="packed" heights="150">
File:CMYK color swatches.svg|Color printing typically uses ink of four colors: [[cyan]], [[magenta]], yellow, and [[Black|key]] (black). When CMY "primaries" are combined at full strength, the resulting "secondary" mixtures are red, green, and blue.
File:SubtractiveColor.svg|Mixing all three theoretically results in black, but imperfect ink formulations do not give true black, which is why an additional ''K'' component is needed.
File:NIEdot367.jpg|An example of color printing from 1902. Combining images in yellow, magenta and cyan creates a full-color picture.  This is called the CMYK color model.
File:Red and green make yellow.png|On a computer display, yellow is created by combining green and red light at the right intensity on a black screen.
</gallery>

Yellow is found between green and red on the spectrum of visible light. It is the color the human eye sees when it looks at light with a [[dominant wavelength]] between 570 and 590 nanometers.

In color printing, yellow is one of the three subtractive primary colors of ink along with [[magenta]] and [[cyan]]. Together with [[black]], they can be overlaid in the right combination to print any full color image. (See the [[CMYK color model]]).  A particular yellow is used, called Process yellow (also known as "pigment yellow", "printer's yellow", and "canary yellow"). Process yellow is not an RGB color, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color that is pure yellow ink.

The yellow on a color television or computer screen is created in a completely different way; by combining green and red light at the right level of intensity. (See [[RGB color model]]).

==== Complementary colors ====
{{See also|Complementary colors}}[[File:PlanckianLocusWithYellowComplements.png|thumb|upright|Complements of yellow have a dominant wavelength in the range 380 to 480&nbsp;nm. The green lines show several possible pairs of complementary colors with respect to different blackbody color temperature neutrals, illustrated by the "[[Planckian locus]]".]]
Traditionally, the complementary color of yellow is purple; the two colors are opposite each other on the color wheel long used by painters.<ref>{{cite book | last1 = Roelofs | first1 = Isabelle | last2 = Petillion | first2 = Fabien | title = La couleur expliquée aux artistes | year=2012 | publisher=Eyrolles | location=Paris | isbn=978-2-212-13486-5}}</ref> [[Vincent van Gogh]], an avid student of color theory, used combinations of yellow and purple in several of his paintings for the maximum contrast and harmony.<ref>{{cite book | first = John | last = Gage | year = 2006 | title = La Couleur dans l'art | pages = 50–51 }}</ref>

Hunt defines that "two colors are complementary when it is possible to reproduce the tristimulus values of a specified achromatic stimulus by an additive mixture of these two stimuli."<ref name=hunt>{{cite book | title = Measuring Color | first = J. W. G. | last = Hunt | year = 1980 | publisher = Ellis Horwood Ltd | isbn = 978-0-7458-0125-4}}</ref> That is, when two colored lights can be mixed to match a specified white (achromatic, non-colored) light, the colors of those two lights are [[Complementary color|complementary]]. This definition, however, does not constrain what version of white will be specified. In the nineteenth century, the scientists [[Hermann Grassmann|Grassmann]] and [[Hermann von Helmholtz|Helmholtz]] did experiments in which they concluded that finding a good complement for spectral yellow was difficult, but that the result was indigo, that is, a wavelength that today's color scientists would call violet or purple. Helmholtz says "Yellow and indigo blue" are complements.<ref>{{cite book | title = Physiological Optics | first = Hermann | last = von Helmholtz | publisher = Dover | year = 1924 | isbn = 978-0-486-44260-0}}</ref> Grassmann reconstructs Newton's category boundaries in terms of wavelengths and says "This indigo therefore falls within the limits of color between which, according to Helmholtz, the complementary colors of yellow lie."<ref>{{cite journal | title = Theory of Compound Colors | first = Hermann Günter | last = Grassmann | journal = Philosophical Magazine | volume =4 | year = 1854 | pages = 254–64 }}</ref>

Newton's own color circle has yellow directly opposite the boundary between indigo and violet. These results, that the complement of yellow is a wavelength shorter than 450&nbsp;nm, are derivable from the modern [[CIE 1931]] system of colorimetry if it is assumed that the yellow is about 580&nbsp;nm or shorter wavelength, and the specified white is the color of a blackbody radiator of temperature 2800 [[kelvin|K]] or lower (that is, the white of an ordinary incandescent light bulb). More typically, with a daylight-colored or around 5000 to 6000 K white, the complement of yellow will be in the blue wavelength range, which is the standard modern answer for the complement of yellow.

Because of the characteristics of paint pigments and use of different [[color wheel]]s, painters traditionally regard the complement of yellow as the color indigo or blue-violet.

==== Lasers ====
[[Laser]]s emitting in the yellow part of the spectrum are less common and more expensive than most other colors.<ref name="laserglow">{{cite web |url=http://www.laserglow.com/index.php?portable |title=Laserglow – Blue, Red, Yellow, Green Lasers |publisher=Laserglow.com |access-date=27 March 2009 |quote=described as an "extremely rare yellow". |archive-date=24 March 2009 |archive-url=https://web.archive.org/web/20090324123802/http://www.laserglow.com/index.php?portable |url-status=live }}</ref> In commercial products diode pumped solid state ([[Diode-pumped solid-state laser|DPSS]]) technology is employed to create the yellow light. An infrared laser diode at 808&nbsp;nm is used to pump a crystal of neodymium-doped yttrium vanadium oxide (Nd:YVO4) or neodymium-doped yttrium aluminum garnet (Nd:YAG) and induces it to emit at two frequencies (281.76&nbsp;THz and 223.39&nbsp;THz: 1064&nbsp;nm and 1342&nbsp;nm wavelengths) simultaneously. This deeper infrared light is then passed through another crystal containing potassium, titanium and phosphorus (KTP), whose non-linear properties generate light at a frequency that is the sum of the two incident beams (505.15&nbsp;THz); in this case corresponding to the wavelength of 593.5&nbsp;nm ("yellow").<ref name="ledmuseum">{{cite web |url=http://ledmuseum.candlepower.us/yelldpss.htm |title=Yellow (593.5&nbsp;nm) DPSS Laser Module |last=Johnson |first=Craig |date=22 March 2009 |publisher=The LED Museum |access-date=27 March 2009 |archive-date=16 February 2009 |archive-url=https://web.archive.org/web/20090216143902/http://ledmuseum.candlepower.us/yelldpss.htm |url-status=live }}</ref> This wavelength is also available, though even more rarely, from a [[helium–neon laser]]. However, this not a true yellow, as it exceeds 590&nbsp;nm. A variant of this same DPSS technology using slightly different starting frequencies was made available in 2010, producing a wavelength of 589&nbsp;nm, which is considered a true yellow color.<ref name="laserglow2">{{cite web |url=http://www.laserglow.com/GRH |title=Laserglow – Blue, Red, Yellow, Green Lasers |publisher=Laserglow.com |access-date=12 August 2011 |archive-date=5 August 2011 |archive-url=https://web.archive.org/web/20110805054301/https://www.laserglow.com/GRH |url-status=live }}</ref> The use of yellow lasers at 589&nbsp;nm and 594&nbsp;nm have recently become more widespread thanks to the field of [[optogenetics]].<ref name="laserglow3">{{cite web |url=http://www.laserglow.com/page/optogenetics |title=Laserglow – Blue, Red, Yellow, Green Lasers |publisher=Laserglow.com |access-date=20 September 2011 |archive-date=15 September 2011 |archive-url=https://web.archive.org/web/20110915023159/http://www.laserglow.com/page/optogenetics |url-status=live }}</ref>