Color temperature: Difference between revisions
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'''Color temperature''' is a parameter describing the [[color]] of a [[visible light]] source by comparing it to the color of [[Black-body radiation|light emitted]] by an [[Black body|idealized opaque, non-reflective body]]. The [[temperature]] of the ideal emitter that matches the color most closely is defined as the color temperature of the original visible light source. The color temperature scale describes only the ''color'' of light emitted by a light source, which may actually be at a different (and often much lower) temperature.<ref>{{Cite web |title=Colour temperature explained {{!}} Adobe |url=https://www.adobe.com/hk_en/creativecloud/video/discover/color-temperature.html |access-date=2024-06-17 |website=www.adobe.com |language=en-HK}}</ref><ref>{{Cite web |title=What is Color Temperature? How Does it Affect Color Performance of the Monitor? |url=https://www.benq.com/en-us/knowledge-center/knowledge/color-temperature.html |access-date=2024-06-17 |website=BenQ |language=en}}</ref> | '''Color temperature''' is a parameter describing the [[color]] of a [[visible light]] source by comparing it to the color of [[Black-body radiation|light emitted]] by an [[Black body|idealized opaque, non-reflective body]]. The [[temperature]] of the ideal emitter that matches the color most closely is defined as the color temperature of the original visible light source. The color temperature scale describes only the ''color'' of light emitted by a light source, which may actually be at a different (and often much lower) temperature.<ref>{{Cite web |title=Colour temperature explained {{!}} Adobe |url=https://www.adobe.com/hk_en/creativecloud/video/discover/color-temperature.html |access-date=2024-06-17 |website=www.adobe.com |language=en-HK}}</ref><ref>{{Cite web |title=What is Color Temperature? How Does it Affect Color Performance of the Monitor? |url=https://www.benq.com/en-us/knowledge-center/knowledge/color-temperature.html |access-date=2024-06-17 |website=BenQ |language=en}}</ref> | ||
Color temperature has applications in [[lighting]],<ref>{{Cite web |date=2022-02-22 |title=Kelvin Color Temperature Chart {{!}} Lighting Color Scale at Lumens |url=https://www.lumens.com/the-edit/the-guides/understanding-kelvin-color-temperature/ |access-date=2024-06-17 |website=www.lumens.com |language=en-US}}</ref> [[photography]],<ref>{{Cite web |last=IoP |date=2023-04-17 |title=Colour Temperature and Its Importance in Photography |url=https://www.institute-of-photography.com/colour-temperature-and-its-importance-in-photography/ |access-date=2024-06-17 |website=Institute of Photography |language=en}}</ref> [[videography]],<ref>{{Cite web |last=Redding |first=Kevin |date=2023-02-10 |title=Why Color Temperature Is Important in Filmmaking and Editing |url=https://www.backstage.com/magazine/article/what-is-color-temperature-75608/ |access-date=2024-06-17 |website=Backstage}}</ref> [[publishing]],<ref>{{Cite web |last= |date=2020-12-23 |title=Correct Color Temperature When Lighting Prints |url=https://gintchinfineart.com/blog/lighting-prints-color-temperature/ |access-date=2024-06-17 |website=Gintchin Fine Art |language=en-US}}</ref> [[manufacturing]], | Color temperature has applications in [[lighting]],<ref>{{Cite web |date=2022-02-22 |title=Kelvin Color Temperature Chart {{!}} Lighting Color Scale at Lumens |url=https://www.lumens.com/the-edit/the-guides/understanding-kelvin-color-temperature/ |access-date=2024-06-17 |website=www.lumens.com |language=en-US}}</ref> [[photography]],<ref>{{Cite web |last=IoP |date=2023-04-17 |title=Colour Temperature and Its Importance in Photography |url=https://www.institute-of-photography.com/colour-temperature-and-its-importance-in-photography/ |access-date=2024-06-17 |website=Institute of Photography |language=en}}</ref> [[videography]],<ref>{{Cite web |last=Redding |first=Kevin |date=2023-02-10 |title=Why Color Temperature Is Important in Filmmaking and Editing |url=https://www.backstage.com/magazine/article/what-is-color-temperature-75608/ |access-date=2024-06-17 |website=Backstage}}</ref> [[publishing]],<ref>{{Cite web |last= |date=2020-12-23 |title=Correct Color Temperature When Lighting Prints |url=https://gintchinfineart.com/blog/lighting-prints-color-temperature/ |access-date=2024-06-17 |website=Gintchin Fine Art |language=en-US}}</ref> [[manufacturing]], and other fields. In practice, color temperature is most meaningful for light sources that correspond somewhat closely to the color of some black body, i.e., light in a range going from red to orange to yellow to [[white]] to bluish white. Although the concept of correlated color temperature extends the definition to any visible light, the color temperature of a green or a purple light rarely is useful information. Color temperature is conventionally expressed in [[kelvin]]s<!-- pluralized – see Kelvin#Usage conventions -->, using the symbol K, which are [[unit of measure|units]] for absolute temperature. | ||
This is distinct from how color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish), exactly the opposite of black body radiation. "Warm" and "cool" in this context is with respect to a traditional aesthetic association of [[Color theory#Warm vs. cool colors|color to warmth or coolness]], not a reference to physical black body temperature. By the [[hue-heat hypothesis]], low color temperatures psychologically evoke warmth, while high color temperatures evoke coolness. The spectral peak of warm-colored light is closer to infrared, and most natural warm-colored light sources emit significant infrared radiation. The fact that "warm" lighting in this sense actually has a "cooler" color temperature often leads to confusion.<ref>See the comments section of this LightNowBlog.com [http://www.lightnowblog.com/2016/07/ama-issues-led-streetlighting-guidance-controversy-ensues/ article] {{webarchive|url=https://web.archive.org/web/20170307123725/http://www.lightnowblog.com/2016/07/ama-issues-led-streetlighting-guidance-controversy-ensues/ |date=2017-03-07 }} on the recommendations of the [[American Medical Association]] to prefer LED-lighting with ''cooler'' color temperatures (i.e. ''warmer'' color).</ref> | This is distinct from how color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish), exactly the opposite of black-body radiation. "Warm" and "cool" in this context is with respect to a traditional aesthetic association of [[Color theory#Warm vs. cool colors|color to warmth or coolness]], not a reference to physical black body temperature. By the [[hue-heat hypothesis]], low color temperatures psychologically evoke warmth, while high color temperatures evoke coolness. The spectral peak of warm-colored light is closer to infrared, and most natural warm-colored light sources emit significant infrared radiation. The fact that "warm" lighting in this sense actually has a "cooler" color temperature often leads to confusion.<ref>See the comments section of this LightNowBlog.com [http://www.lightnowblog.com/2016/07/ama-issues-led-streetlighting-guidance-controversy-ensues/ article] {{webarchive|url=https://web.archive.org/web/20170307123725/http://www.lightnowblog.com/2016/07/ama-issues-led-streetlighting-guidance-controversy-ensues/ |date=2017-03-07 }} on the recommendations of the [[American Medical Association]] to prefer LED-lighting with ''cooler'' color temperatures (i.e. ''warmer'' color).</ref> | ||
==Categorizing different lighting== | ==Categorizing different lighting== | ||
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===The Sun=== | ===The Sun=== | ||
The [[Sun]] closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is | The [[Sun]] closely approximates a black-body radiator. The effective temperature, defined by the total radiative power per square unit, is 5,772 K.<ref>{{cite web |last=Williams |first=David R. |year=2022 |title=Sun Fact Sheet |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |publisher=[[NASA]] |access-date=2023-03-24 |url-status=live |archive-url=https://web.archive.org/web/20230316150908/https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |archive-date=2023-03-16 }}</ref> The color temperature of [[sunlight]] above the atmosphere is about 5,900 K.<ref>{{cite web |url=http://www.crisp.nus.edu.sg/~research/tutorial/optical.htm |title=Principles of Remote Sensing |publisher=[[Centre for Remote Imaging, Sensing, and Processing|CRISP]] |access-date=2012-06-18 |url-status=live |archive-url=https://web.archive.org/web/20120702174159/http://www.crisp.nus.edu.sg/~research/tutorial/optical.htm |archive-date=2012-07-02 }}</ref> | ||
The Sun may appear red, orange, yellow, or white from Earth, depending on [[position of the Sun|its position]] in the sky. The changing color of the Sun over the course of the day is mainly a result of the [[scattering]] of sunlight and is not due to changes in black-body radiation. [[Rayleigh scattering]] of sunlight by [[Earth's atmosphere]] causes the blue color of the sky, which tends to scatter blue light more than red light. | The Sun may appear red, orange, yellow, or white from Earth, depending on [[position of the Sun|its position]] in the sky. The changing color of the Sun over the course of the day is mainly a result of the [[scattering]] of sunlight and is not due to changes in black-body radiation. [[Rayleigh scattering]] of sunlight by [[Earth's atmosphere]] causes the blue color of the sky, which tends to scatter blue light more than red light. | ||
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Some [[daylight]] in the early [[morning]] and late [[afternoon]] (the [[golden hour (photography)|golden hours]]) has a lower ("warmer") color temperature due to increased [[light scattering by particles|scattering]] of shorter-wavelength sunlight by [[atmospheric particulates]] – an [[optical phenomenon]] called the [[Tyndall effect]]. | Some [[daylight]] in the early [[morning]] and late [[afternoon]] (the [[golden hour (photography)|golden hours]]) has a lower ("warmer") color temperature due to increased [[light scattering by particles|scattering]] of shorter-wavelength sunlight by [[atmospheric particulates]] – an [[optical phenomenon]] called the [[Tyndall effect]]. | ||
Daylight has a spectrum similar to that of a black body with a correlated color temperature of | Daylight has a spectrum similar to that of a black body with a correlated color temperature of 6,500 K ([[CIE Standard Illuminant D65|D65]] viewing standard) or 5,500 K (daylight-balanced photographic film standard). | ||
[[File:Color temperature black body 800-12200K.svg|thumb|center|512px|Approximation of the hues of the Planckian locus as a function of the kelvin temperature, rendered with a white point near | [[File:Color temperature black body 800-12200K.svg|thumb|center|512px|Approximation of the hues of the Planckian locus as a function of the kelvin temperature, rendered with a white point near 6,500 K, not accounting for [[chromatic adaptation]]]] | ||
For colors based on black-body theory, blue occurs at higher temperatures, whereas red occurs at lower temperatures. This is the opposite of the cultural associations attributed to colors, in which "red" is "hot", and "blue" is "cold".<ref> | For colors based on black-body theory, blue occurs at higher temperatures, whereas red occurs at lower temperatures. This is the opposite of the cultural associations attributed to colors, in which "red" is "hot", and "blue" is "cold".<ref> | ||
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| url = https://books.google.com/books?id=j728wJySfyQC&q=blue+cool+red+hot+color-temperature+sun | | url = https://books.google.com/books?id=j728wJySfyQC&q=blue+cool+red+hot+color-temperature+sun | ||
}}</ref> | }}</ref> | ||
{{color swatch |1=#94b1ff |2=The color of an infinitely hot blackbody. |3=left}} | |||
===Infinite temperature=== | |||
As the temperature of a black-body radiator approaches positive infinity, its color converges to [[CIE 1931 color space|CIE xy]] coordinates (0.2399, 0.2340),<ref>Using [[Planck's law]] combined with the [https://www.cie.co.at/datatable/cie-1931-colour-matching-functions-2-degree-observer CIE color-matching functions]</ref> corresponding to an [[sRGB]] value of (148, 177, 255) or #94b1ff,<ref>{{cite web|url=https://tagteam.harvard.edu/hub_feeds/3917/feed_items/3426240|title=The Color of Infinite Temperature|website=tagteam.harvard.edu|date=2022-01-16|access-date=2026-04-20}}</ref> a light blue color known as perano.<ref>{{cite web|url=https://www.htmlcsscolor.com/hex/94B1FF|title=Html Css Color HEX #94B1FF|website=htmlcsscolor.com|access-date=2026-04-20}}</ref> This is because of the [[Rayleigh-Jeans law]], which states that at frequencies much lower than the peak frequency of a black-body radiator, [[Spectral power distribution|spectral power]] is inversely proportional to the fourth power of the wavelength. | |||
==Applications== | ==Applications== | ||
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[[Digital camera]]s, web graphics, [[DVD]]s, etc., are normally designed for a 6500 K color temperature. The [[sRGB standard]] commonly used for images on the Internet stipulates a 6500 K display [[white point]]. | [[Digital camera]]s, web graphics, [[DVD]]s, etc., are normally designed for a 6500 K color temperature. The [[sRGB standard]] commonly used for images on the Internet stipulates a 6500 K display [[white point]]. | ||
[[Microsoft Windows]] prior to [[Windows 10]] are use [[sRGB]] as default display color space, and use 6500 K as default display color temperature. [[Windows 10 1607]] have supports for [[ | [[Microsoft Windows]] prior to [[Windows 10]] are use [[sRGB]] as default display color space, and use 6500 K as default display color temperature. [[Windows 10 1607]] have supports for [[High Dynamic Range]].<ref>{{Cite web |last=windows-driver-content |title=HEVC 10-Bit HDR Streaming Playback Test 1 |url=https://learn.microsoft.com/en-us/windows-hardware/test/hlk/testref/7ecb10c2-5c2d-4f67-a29c-6ffeb9da2812 |access-date=2025-05-14 |website=learn.microsoft.com |language=en-us}}</ref> [[Windows 11 22H2]] have supports for Auto Color Management (ACM) which further optimized for [[OLED]] and/or [[wide-color gamut]] monitors by reading [[DisplayID]] data.<ref>{{Cite web |title=Auto color management in Windows 11 - Microsoft Support |url=https://support.microsoft.com/en-us/windows/auto-color-management-in-windows-11-64a4de7f-9c93-43ec-bdf1-3b12ffa0870b |access-date=2024-09-04 |website=support.microsoft.com}}</ref> | ||
Apple [[iOS]], [[iPadOS]] and [[macOS]] | Apple [[iOS]], [[iPadOS]] and [[macOS]] use [[sRGB]] and [[DCI-P3]] as default display color spaces.<ref>{{Cite web |title=Use reference modes with your Apple display |url=https://support.apple.com/en-us/108321 |access-date=2025-03-30 |website=Apple Support |language=en}}</ref> | ||
===TV, video, and digital still cameras=== | ===TV, video, and digital still cameras=== | ||
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==Color rendering index== | ==Color rendering index== | ||
{{Main|Color rendering index}} | {{Main|Color rendering index}} | ||
The [[International Commission on Illumination|CIE]] | The [[International Commission on Illumination|CIE]] color rendering index (CRI) is a method to determine how well a light source's illumination of eight sample patches compares to the illumination provided by a reference source. Cited together, the CRI and CCT give a numerical estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is. | ||
==Spectral power distribution== | ==Spectral power distribution== | ||
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==See also== | ==See also== | ||
* [[Brightness temperature]] | * [[Brightness temperature]] | ||
* [[CIE 1931 color space]] | |||
* [[Color balance]] | * [[Color balance]] | ||
* [[Metamerism (color)#Metamerism and industry|Color metamerism]] | |||
* [[Colored fire]] | |||
* [[Effective temperature]] | * [[Effective temperature]] | ||
* [[Kruithof curve]] | * [[Kruithof curve]] | ||
* [[Luminous efficacy]] | * [[Luminous efficacy]] | ||
* [[Overillumination]] | * [[Overillumination]] | ||
* [[Whiteness (colorimetry)|Whiteness]] | * [[Whiteness (colorimetry)|Whiteness]] | ||