WordNet

the luminous flux incident on a unit area (同)illumination

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/21 06:07:00」(JST)

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A lux meter for measuring illuminances in work environments.

In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance.^[1]

In SI derived units these are measured in lux (lx) or lumens per square metre (cd·sr·m⁻²). In the CGS system, the unit of illuminance is the phot, which is equal to 10000 lux. The foot-candle is a non-metric unit of illuminance that is used in photography.^[2]

Illuminance was formerly often called brightness, but this leads to confusion with other uses of the word, such as to mean luminance. "Brightness" should never be used for quantitative description, but only for nonquantitative references to physiological sensations and perceptions of light.

The human eye is capable of seeing somewhat more than a 2 trillion-fold range: The presence of white objects is somewhat discernible under starlight, at 6995500000000000000♠5×10⁻⁵ lux, while at the bright end, it is possible to read large text at 10⁸ lux, or about 1000 times that of direct sunlight, although this can be very uncomfortable and cause long-lasting afterimages.^{[citation needed]}

Astronomy

In astronomy, the illuminance stars cast on the Earth's atmosphere is used as a measure of their brightness. The usual units are apparent magnitudes in the visible band.^[3] V-magnitudes can be converted to lux using the formula^[4]

,

where E_v is the illuminance in lux, and M_v is the apparent magnitude. The reverse conversion is

.

References

^ Luminous exitance Drdrbill.com
^ One phot = 929.030400001 foot-candles, according to http://www.unitconversion.org/unit_converter/illumination.html
^ Schlyter, Paul. "Radiometry and photmetry in astronomy FAQ, section 7".
^ "Formulae for converting to and from astronomy-relevant units" (PDF). Retrieved Nov 23, 2013.

Knowledgedoor, LLC (2005) Library of Units and Constants: Illuminance Quantity
Illuminance Converter

External links

A Kodak guide to Estimating Luminance and Illuminance using a camera's exposure meter. Also available in PDF form.
Autodesk Design Academy - Measuring Light Levels

SI photometry quantities

Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Symbol	Notes
Luminous energy	Q_v ^{[nb 2]}	lumen second	lm⋅s	T⋅J ^{[nb 3]}	Units are sometimes called talbots.
Luminous flux / Luminous power	Φ_v ^{[nb 2]}	lumen (= cd⋅sr)	lm	J ^{[nb 3]}	Luminous energy per unit time.
Luminous intensity	I_v	candela (= lm/sr)	cd	J ^{[nb 3]}	Luminous power per unit solid angle.
Luminance	L_v	candela per square metre	cd/m²	L⁻²⋅J	Luminous power per unit solid angle per unit projected source area. Units are sometimes called nits.
Illuminance	E_v	lux (= lm/m²)	lx	L⁻²⋅J	Luminous power incident on a surface.
Luminous exitance / Luminous emittance	M_v	lux	lx	L⁻²⋅J	Luminous power emitted from a surface.
Luminous exposure	H_v	lux second	lx⋅s	L⁻²⋅T⋅J
Luminous energy density	ω_v	lumen second per cubic metre	lm⋅s⋅m⁻³	L⁻³⋅T⋅J
Luminous efficacy	η ^{[nb 2]}	lumen per watt	lm/W	M⁻¹⋅L⁻²⋅T³⋅J	Ratio of luminous flux to radiant flux.
Luminous efficiency / Luminous coefficient	V			1
See also: SI · Photometry · Radiometry

^ Standards organizations recommend that photometric quantities be denoted with a suffix "v" (for "visual") to avoid confusion with radiometric or photon quantities. For example: USA Standard Letter Symbols for Illuminating Engineering USAS Z7.1-1967, Y10.18-1967
^ ^a ^b ^c Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
^ ^a ^b ^c "J" here is the symbol for the dimension of luminous intensity, not the symbol for the unit joules.

English Journal

Oxygen-induced retinopathy induces short-term glial stress and long-term impairment of photoentrainment in mice.

Mehdi MK, Sage-Ciocca D, Challet E, Malan A, Hicks D.Author information Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212 Université de Strasbourg, 5 rue Blaise Pascal, 67084, Strasbourg, Cedex, France.AbstractBACKGROUND: Retinopathy of prematurity is a serious potentially blinding disease of pre-term infants. There is extensive vascular remodeling and tissue stress, but data concerning alterations in retinal neurons and glia, and long-term functional sequelae are still incomplete.
Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie.Graefes Arch Clin Exp Ophthalmol.2014 Feb 9. [Epub ahead of print]
BACKGROUND: Retinopathy of prematurity is a serious potentially blinding disease of pre-term infants. There is extensive vascular remodeling and tissue stress, but data concerning alterations in retinal neurons and glia, and long-term functional sequelae are still incomplete.METHODS: ROP was induced
PMID 24509649

The effect of ambient illumination on handheld display image quality.

Liu P, Zafar F, Badano A.Author information Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, FDA, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA.AbstractHandheld devices such as smartphones and tablets are becoming useful in the medical field, as they allow physicians, radiologists, and researchers to analyze images with the benefit of mobile accessibility. However, for handheld devices to be effective, the display must be able to perform well in a wide range of ambient illumination conditions. We conducted visual experiments to quantify user performance for testing the image quality of two current-generation devices in different ambient illumination conditions while measuring ambient light levels with a real-time illuminance meter. We found and quantified that due to the high reflectivity of handheld devices, performance deteriorates as the user moves from dark areas into environments of greater ambient illumination. The quantitative analysis suggests that differences in display reflection coefficients do not affect the low illumination performance of the device but rather the performance at higher levels of illumination.
Journal of digital imaging.J Digit Imaging.2014 Feb;27(1):12-8. doi: 10.1007/s10278-013-9636-1.
Handheld devices such as smartphones and tablets are becoming useful in the medical field, as they allow physicians, radiologists, and researchers to analyze images with the benefit of mobile accessibility. However, for handheld devices to be effective, the display must be able to perform well in a
PMID 24113844

Variations in daylight as a contextual cue for estimating season, time of day, and weather conditions.

Granzier JJ, Valsecchi M.Author information Justus Liebig University, Department of Psychology, Giessen, Germany.AbstractExperience and experiments on human color constancy (i.e., Arend & Reeves, 1986; Craven & Foster, 1992) tell us that we are capable of judging the illumination. However, when asked to make a match of the illuminant's color and brightness, human observers seem to be quite poor (Granzier, Brenner, & Smeets, 2009a). Here we investigate whether human observers use (rather than match) daylight for estimating ecologically important dimensions: time of year, time of day, and outdoor temperature. In the first three experiments we had our observers evaluate calibrated color images of an outdoor urban scene acquired throughout a year. Although some observers could estimate the month and the temperature, overall they were quite poor at judging the time of day. In particular, observers were not able to discriminate between morning and afternoon pictures even when they were allowed to compare multiple images captured on the same day (Experiment 3). However, observers could distinguish between midday and sunset and sunrise daylight. Classification analysis showed that, given a perfect knowledge of its variation, an ideal observer could have performed the task over chance only considering the average chromatic variation in the picture. Instead, our observers reported using shadows to detect the position of the sun in order to estimate the time of day. However, this information is highly unreliable without knowledge of the orientation of the scene. In Experiment 4 we used an LED chamber in order to present our observers with lights whose chromaticity and illuminance varied along the daylight locus, thus isolating the light cues from the sun position cue. We conclude that discriminating the slight variations in chromaticity and brightness, which potentially distinguish morning and afternoon illuminations, lies beyond the ability of human observers.
Journal of vision.J Vis.2014 Jan 24;14(1). pii: 22. doi: 10.1167/14.1.22.
Experience and experiments on human color constancy (i.e., Arend & Reeves, 1986; Craven & Foster, 1992) tell us that we are capable of judging the illumination. However, when asked to make a match of the illuminant's color and brightness, human observers seem to be quite poor (Granzier, Bren
PMID 24464161

Japanese Journal

弱視者に配慮した低照度環境における階段照明方式の検討

片岡加奈恵,岩田三千子
日本建築学会環境系論文集 80(712), 519-526, 2015-06
NAID 40020502100

照度変化による自律神経系への影響評価のための指尖容積脈波の有効性の検討

小谷賢太郎,後藤雅也,鈴木哲 [他]
システム制御情報学会研究発表講演会講演論文集 59, 4p, 2015-05-20
NAID 40020475657

照明装置からの距離-照度モデルの提案と位置推定への応用

守谷一希,荒川豊,安本慶一
情報処理学会研究報告. UBI, [ユビキタスコンピューティングシステム] 2015-UBI-46(2), 1-8, 2015-05-04
本稿では,照明装置を点灯した際の照明装置からの距離と照度の実測値に基づいた関係モデルを提案する.また,その距離-照度モデルを利用した三辺測量方式に基づく屋内位置推定手法を提案する.照度を用いた位置推定の先行研究として,フィンガープリンティング方式に基づく屋内位置推定手法が提案されている.その手法の問題点として,対象空間内の既設照明装置を利用するため照明装置種類ごとの距離-照度モデルが必要であること …
NAID 110009895725

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