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{{For|the luminosity function in astronomy|Luminosity function (astronomy)}} | |||
[[Image:Luminosity.png|thumb|right|400px|[[Photopic vision|Photopic]] (black) and [[scotopic vision|scotopic]] (green) luminosity functions.<ref name="scvl" group=c/> The photopic includes the CIE 1931 standard<ref name="ciexyz31" group=c/> (solid), the Judd–Vos 1978 modified data<ref name="vljv" group=c/> (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data<ref name="ssvl2" group=c/> (dotted). The horizontal axis is wavelength in [[Nanometre|nm]].]] | |||
[[Image:Srgbspectrum.png|thumb|right|400px|]] | |||
The '''luminosity function''' or '''luminous efficiency function''' describes the average [[spectral sensitivity]] of human visual perception of brightness. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It should not be considered perfectly accurate in every case, but it is a very good representation of visual sensitivity of the human eye and it is valuable as a baseline for experimental purposes. | |||
The CIE luminosity function <math>\overline{y}(\lambda)</math> or <math>V(\lambda)\,</math> is a standard function established by the [[Commission Internationale de l'Éclairage]] (CIE) and may be used to convert radiant energy into luminous (i.e., visible) energy. It also forms the central [[CIE 1931 color space#Color matching functions|color matching function]] in the [[CIE 1931 color space]]. | |||
== Details == | |||
There are two luminosity functions in common use. For everyday light levels, the [[photopic vision|photopic]] luminosity function best approximates the response of the human eye. For low light levels, the response of the human eye changes, and the [[scotopic vision|scotopic]] curve applies. The photopic curve is the CIE standard curve used in the CIE 1931 color space. | |||
The [[luminous flux]] (or visible energy) in a light source is defined by the photopic luminosity function. The following equation calculates the total luminous flux in a source of light. | |||
:<math>F=683.002\ \mathrm{lm/W}\cdot \int^\infin_0 \overline{y}(\lambda) J(\lambda) d\lambda</math> | |||
where | |||
:<math>F\,</math> is the luminous flux in [[lumen (unit)|lumen]]s, | |||
:<math>J(\lambda)\,</math> is the [[spectral power distribution]] of the radiation (power per unit wavelength), in watts per metre. | |||
:<math>\overline{y}(\lambda)</math> (also known as <math>V(\lambda)\,</math>) is the standard luminosity function (which is dimensionless). | |||
:<math>\lambda\,</math> is wavelength in metres. | |||
Formally, the integral is the [[inner product]] of the luminosity function with the light spectrum.<ref name="Charles2003"/> In practice, the integral is replaced by a sum over discrete wavelengths for which tabulated values of the luminosity function are available. The [[International Commission on Illumination|CIE]] distributes standard tables with luminosity function values at 5 nm intervals from 380 nm to 780 nm.<ref name="CIEdocs" group=cie/> | |||
The standard luminosity function is normalized to a peak value of unity at 555 nm (see [[luminous coefficient]]). The value of the constant in front of the integral is usually rounded off to 683 lm/W. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function. The lumen is defined to be unity for a radiant energy of 1/683 watt at a frequency of 540 THz, which corresponds to a standard air wavelength of 555.016 nm rather than 555 nm, which is the peak of the luminosity curve. The value of <math>\overline{y}(\lambda)</math> is 0.999997 at 555.016 nm, so that a value of 683/0.999997 = 683.002 is the multiplicative constant.<ref name="Wyszecki2000"/> | |||
The number 683 is connected to the modern (1979) definition of the [[candela]], the unit of [[luminous intensity]].<ref name="candela" group=cie/> This arbitrary number made the new definition give numbers equivalent to those from the old definition of the candela. | |||
== Improvements to the standard == | |||
The CIE 1924 photopic <math>V(\lambda)</math> luminosity function,<ref name="CIE1926" group=cie/> which is included in the CIE 1931 color-matching functions as the ''y'' function, has long been acknowledged to underestimate the contribution of the blue end of the spectrum to perceived luminance. There have been numerous attempts to improve the standard function, to make it more representative of human vision. Judd in 1951,<ref name="Judd1975"/> improved by Vos in 1978,<ref name="Vos1978"/> resulted in a function known as CIE <math>V_M(\lambda)</math>.<ref name="Stiles1955"/> More recently, Sharpe, Stockman, Jagla & Jägle (2005) developed a function consistent with the [http://www.cvrl.org/cones.htm Stockman & Sharpe cone fundamentals];<ref name="Sharpe2005"/> their curves are plotted in the figure above. | |||
== Scotopic luminosity == | |||
For very low levels of intensity ([[scotopic vision]]), the sensitivity of the eye is mediated by rods, not cones, and shifts toward the [[violet (color)|violet]], peaking around 507 nm for young eyes; the sensitivity is equivalent to 1699 lm/W<ref name="Kohei2004"/> or 1700 lm/W<ref name="Casimer1998"/> at this peak. | |||
The standard scotopic luminosity function or <math>V^\prime(\lambda)</math> was adopted by the CIE in 1951, based on measurements by Wald (1945) and by Crawford (1949).[http://www.cvrl.org/database/text/lum/scvl.htm] | |||
== Color blindness == | |||
[[File:LuminosityCurve2.svg|right|thumb|400px|Protanopic (green) and deuteranopic (red) luminosity functions.<ref name="judd">{{cite book|last=Judd|first=Deane B.|title=Contributions to Color Science|year=1979|publisher=NBS|location=Washington D.C. 20234|url=http://books.google.ru/books?id=jgz_iI8NAzYC&pg=PA316|page=316}}</ref> For comparison, the standard photopic curve is shown in yellow.]] | |||
[[Color blindness]] changes the sensitivity of the eye as a function of wavelength. For people with [[protanopia]], the peak of the eye's response is shifted toward the short-wave part of the spectrum (approximately 540 nm), while for people suffering [[deuteranopia]], there is a slight shift in the peak of the spectrum, to about 560 nm.<ref name="judd" /> People with protanopia have essentially no sensitivity to light of wavelengths more than 670 nm. | |||
Most [[mammals]] other than [[primates]] have the same luminosity function as people with protanopia. This makes it possible to study the nocturnal life of animals by illuminating the scene with long-wavelength red light that they can't see.<ref>{{cite journal|coauthors=I. S. McLennan & J. Taylor-Jeffs|title=The use of sodium lamps to brightly illuminate mouse houses during their dark phases|journal=Laboratory Animals|year=2004|volume=38|pages=384–392|pmid=15479553|doi= 10.1258/0023677041958927|url=http://la.rsmjournals.com/content/38/4/384.full.pdf}}</ref> | |||
For older people with normal color vision, the [[crystalline lens]] may become slightly yellow due to [[cataract]]s, which moves the maximum of sensitivity to the red part of the spectrum and narrows the range of perceived wavelengths. | |||
== See also == | |||
* [[A-weighting]], the sound equivalent | |||
* [[Apparent brightness]] | |||
* [[Color vision]] | |||
* [[Quantum efficiency]], the image sensor equivalent | |||
== References == | |||
{{reflist|3|refs= | |||
<ref name="Charles2003">{{cite book | |||
| title = Digital Video and HDTV: Algorithms and Interfaces | |||
| author = Charles A. Poynton | |||
| publisher = Morgan Kaufmann | |||
| year = 2003 | |||
| isbn = 1-55860-792-7 | |||
| url = http://books.google.com/?id=ra1lcAwgvq4C&pg=RA1-PA205&dq=luminance+dot-product | |||
}}</ref> | |||
<ref name="Wyszecki2000">{{cite book | |||
| author = Wyszecki, Günter and Stiles, W.S. | |||
| title = Color Science - Concepts and Methods, Quantitative Data and Formulae | |||
| edition = 2nd | |||
| publisher = Wiley-Interscience | |||
| year = 2000 | |||
| isbn = 0-471-39918-3 | |||
}}</ref> | |||
<ref name="Judd1975">{{cite book | |||
| author = Judd, Deane B. and Wyszecki, Günter | |||
| title = Color in Business, Science and Industry | |||
| edition = 3rd | |||
| publisher = John Wiley | |||
| year = 1975 | |||
| isbn = 0-471-45212-2 | |||
}}</ref> | |||
<ref name="Vos1978">{{cite journal | |||
| author = Vos, J. J. | |||
| title = Colorimetric and photometric properties of a 2° fundamental observer | |||
| journal = Color Research and Application | |||
| year = 1978 | |||
| volume = 3 | |||
| issue = 3 | |||
| pages = 125–128 | |||
| doi = 10.1002/col.5080030309 | |||
}}</ref> | |||
<ref name="Stiles1955">{{cite journal | |||
| author1 = Stiles, W. S. | |||
| author2 = Burch, J. M. | |||
| title = Interim report to the Commission Internationale de l'Eclairage Zurich 1955, on the National Physical Laboratory's investigation of colour-matching | |||
| journal = Optica Acta | |||
| year = 1955 | |||
| volume = 2 | |||
| pages = 168–181 | |||
| bibcode = 1955AcOpt...2..168S | |||
| doi = 10.1080/713821039 | |||
| issue = 4 | |||
}}</ref> | |||
<ref name="Sharpe2005">{{cite journal | |||
| author1 = Sharpe, L. T. | |||
| author2 = Stockman, A. | |||
| author3 = Jagla, W. | |||
| author4 = Jägle, H. | |||
| year = 2005 | |||
| title = A luminous efficiency function, V*(λ), for daylight adaptation | |||
| url = http://calendar.arvo.org/5/11/3/Sharpe-2005-jov-5-11-3.pdf | |||
| journal = Journal of Vision | |||
| volume = 5 | |||
| number = 11 | |||
| pages = 948–968 | |||
| doi = 10.1167/5.11.3 | |||
}}</ref> | |||
<ref name="Kohei2004">{{cite book | |||
| title = Light Pollution Handbook | |||
| author1 = Kohei Narisada | |||
| author2 = Duco Schreuder | |||
| publisher = Springer | |||
| year = 2004 | |||
| isbn = 1-4020-2665-X | |||
}}</ref> | |||
<ref name="Casimer1998">{{cite book | |||
| title = Handbook of Applied Photometry | |||
| author = Casimer DeCusatis | |||
| publisher = Springer | |||
| year = 1998 | |||
| isbn = 1-56396-416-3 | |||
}}</ref> | |||
}} | |||
=== CIE documents === | |||
{{reflist|group=cie|refs= | |||
<ref name="CIEdocs" group=cie>{{cite web | |||
| url = http://www.cie.co.at/main/freepubs.html | |||
| title = CIE Free Documents for Download | |||
}}</ref> | |||
<ref name="candela" group=cie>16th [[General Conference on Weights and Measures|Conférence générale des poids et mesures]] Resolution 3, CR, 100 (1979), and ''Metrologia'', '''16''', 56 (1980).</ref> | |||
<ref name="CIE1926" group=cie>{{cite book | |||
| author = CIE | |||
| title = Commission internationale de l'Eclairage proceedings, 1924 | |||
| publisher = Cambridge University Press, Cambridge | |||
| year = 1926 | |||
}}</ref> | |||
}} | |||
=== Curve data === | |||
{{reflist|group=c|refs= | |||
<ref name="scvl">{{cite web | |||
| title = CIE Scotopic luminosity curve (1951) | |||
| url = http://www.cvrl.org/database/text/lum/scvl.htm | |||
| archiveurl = http://web.archive.org/web/20081228115119/http://www.cvrl.org/database/text/lum/scvl.htm | |||
| archivedate = 2008-12-28 | |||
}}</ref> | |||
<ref name="ciexyz31">{{cite web | |||
| title = CIE (1931) 2-deg color matching functions | |||
| url = http://www.cvrl.org/database/text/cmfs/ciexyz31.htm | |||
| archiveurl = http://web.archive.org/web/20081228084047/http://www.cvrl.org/database/text/cmfs/ciexyz31.htm | |||
| archivedate = 2008-12-28 | |||
}}</ref> | |||
<ref name="vljv">{{cite web | |||
| title = Judd–Vos modified CIE 2-deg photopic luminosity curve (1978) | |||
| url = http://www.cvrl.org/database/text/lum/vljv.htm | |||
| archiveurl = http://web.archive.org/web/20081228083025/http://www.cvrl.org/database/text/lum/vljv.htm | |||
| archivedate = 2008-12-28 | |||
}}</ref> | |||
<ref name="ssvl2">{{cite web | |||
| title = Sharpe, Stockman, Jagla & Jägle (2005) 2-deg V*(l) luminous efficiency function | |||
| url = http://www.cvrl.org/database/text/lum/ssvl2.htm | |||
| archiveurl = http://web.archive.org/web/20070927222337/http://www.cvrl.org/database/text/lum/ssvl2.htm | |||
| archivedate = 2007-09-27 | |||
}}</ref> | |||
}} | |||
== External links == | |||
* [http://www.cvrl.org/lumindex.htm Color and Research Vision Laboratory - luminous efficiency data tables] | |||
[[Category:Physical quantities]] | |||
[[Category:Photometry]] |
Revision as of 01:30, 5 December 2013
28 year-old Painting Investments Worker Truman from Regina, usually spends time with pastimes for instance interior design, property developers in new launch ec Singapore and writing. Last month just traveled to City of the Renaissance.
The luminosity function or luminous efficiency function describes the average spectral sensitivity of human visual perception of brightness. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It should not be considered perfectly accurate in every case, but it is a very good representation of visual sensitivity of the human eye and it is valuable as a baseline for experimental purposes.
The CIE luminosity function or is a standard function established by the Commission Internationale de l'Éclairage (CIE) and may be used to convert radiant energy into luminous (i.e., visible) energy. It also forms the central color matching function in the CIE 1931 color space.
Details
There are two luminosity functions in common use. For everyday light levels, the photopic luminosity function best approximates the response of the human eye. For low light levels, the response of the human eye changes, and the scotopic curve applies. The photopic curve is the CIE standard curve used in the CIE 1931 color space.
The luminous flux (or visible energy) in a light source is defined by the photopic luminosity function. The following equation calculates the total luminous flux in a source of light.
where
- is the luminous flux in lumens,
- is the spectral power distribution of the radiation (power per unit wavelength), in watts per metre.
- (also known as ) is the standard luminosity function (which is dimensionless).
- is wavelength in metres.
Formally, the integral is the inner product of the luminosity function with the light spectrum.[1] In practice, the integral is replaced by a sum over discrete wavelengths for which tabulated values of the luminosity function are available. The CIE distributes standard tables with luminosity function values at 5 nm intervals from 380 nm to 780 nm.[cie 1]
The standard luminosity function is normalized to a peak value of unity at 555 nm (see luminous coefficient). The value of the constant in front of the integral is usually rounded off to 683 lm/W. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function. The lumen is defined to be unity for a radiant energy of 1/683 watt at a frequency of 540 THz, which corresponds to a standard air wavelength of 555.016 nm rather than 555 nm, which is the peak of the luminosity curve. The value of is 0.999997 at 555.016 nm, so that a value of 683/0.999997 = 683.002 is the multiplicative constant.[2] The number 683 is connected to the modern (1979) definition of the candela, the unit of luminous intensity.[cie 2] This arbitrary number made the new definition give numbers equivalent to those from the old definition of the candela.
Improvements to the standard
The CIE 1924 photopic luminosity function,[cie 3] which is included in the CIE 1931 color-matching functions as the y function, has long been acknowledged to underestimate the contribution of the blue end of the spectrum to perceived luminance. There have been numerous attempts to improve the standard function, to make it more representative of human vision. Judd in 1951,[3] improved by Vos in 1978,[4] resulted in a function known as CIE .[5] More recently, Sharpe, Stockman, Jagla & Jägle (2005) developed a function consistent with the Stockman & Sharpe cone fundamentals;[6] their curves are plotted in the figure above.
Scotopic luminosity
For very low levels of intensity (scotopic vision), the sensitivity of the eye is mediated by rods, not cones, and shifts toward the violet, peaking around 507 nm for young eyes; the sensitivity is equivalent to 1699 lm/W[7] or 1700 lm/W[8] at this peak.
The standard scotopic luminosity function or was adopted by the CIE in 1951, based on measurements by Wald (1945) and by Crawford (1949).[1]
Color blindness
Color blindness changes the sensitivity of the eye as a function of wavelength. For people with protanopia, the peak of the eye's response is shifted toward the short-wave part of the spectrum (approximately 540 nm), while for people suffering deuteranopia, there is a slight shift in the peak of the spectrum, to about 560 nm.[9] People with protanopia have essentially no sensitivity to light of wavelengths more than 670 nm.
Most mammals other than primates have the same luminosity function as people with protanopia. This makes it possible to study the nocturnal life of animals by illuminating the scene with long-wavelength red light that they can't see.[10]
For older people with normal color vision, the crystalline lens may become slightly yellow due to cataracts, which moves the maximum of sensitivity to the red part of the spectrum and narrows the range of perceived wavelengths.
See also
- A-weighting, the sound equivalent
- Apparent brightness
- Color vision
- Quantum efficiency, the image sensor equivalent
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
CIE documents
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
Curve data
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
External links
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