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Lux feat. Ismail Delija - Janko DissTrack ( Official Music Video)
Lux feat. Ismail Delija - Janko DissTrack ( Official Music Video)
Published: 2017/09/16
Channel: Lux27
SO YOU WANT TO MAIN LUX
SO YOU WANT TO MAIN LUX
Published: 2017/09/19
Channel: BrickyOrchid8
HOW TO PLAY LUX LIKE A TRUE S+ RANK GOD - League of Legends Commentary
HOW TO PLAY LUX LIKE A TRUE S+ RANK GOD - League of Legends Commentary
Published: 2016/12/27
Channel: Anklespankin
KayPea - Best LUX
KayPea - Best LUX
Published: 2017/09/17
Channel: League of Legends GGWP
Loaded Lux vs Arsonal | UDubb
Loaded Lux vs Arsonal | UDubb's Alpha N Omega Rap Battle
Published: 2017/08/26
Channel: UDubb Network Battle League
Cheleti Obontike Bhalobeshechilo | Eid Drama | Lux Bhalobashar Shourobher Golpo
Cheleti Obontike Bhalobeshechilo | Eid Drama | Lux Bhalobashar Shourobher Golpo
Published: 2017/09/02
Channel: LUX Bangladesh
Presenting the 16th Lux Style Awards (Part 1)
Presenting the 16th Lux Style Awards (Part 1)
Published: 2017/05/20
Channel: Lux Pakistan YouTube
DeLUX Jam (LuxMix) | League of Legends Community Collab
DeLUX Jam (LuxMix) | League of Legends Community Collab
Published: 2016/01/01
Channel: League of Legends Community
Dampotto | Eid Drama | Siam, Maria Nur | Lux Bhalobashar Shourobher Golpo
Dampotto | Eid Drama | Siam, Maria Nur | Lux Bhalobashar Shourobher Golpo
Published: 2017/09/05
Channel: LUX Bangladesh
LUX INSTAKILLS - BEST Oneshots + Fast Combo [ GODZU ]
LUX INSTAKILLS - BEST Oneshots + Fast Combo [ GODZU ]
Published: 2017/09/20
Channel: Godzu
LUX ONESHOTS!! Unreal DAMAGE!! [ League of Legends ]
LUX ONESHOTS!! Unreal DAMAGE!! [ League of Legends ]
Published: 2017/07/29
Channel: Godzu
Best Lux Korea Mid vs Vel
Best Lux Korea Mid vs Vel'Koz | Korea High Elo
Published: 2017/02/07
Channel: BestLeagueTW
LUX WET DREAM
LUX WET DREAM
Published: 2017/04/16
Channel: League Nation
LUX FULL DMG FAST COMBO
LUX FULL DMG FAST COMBO
Published: 2017/04/15
Channel: LoL Slow Motions
Miss Match | Eid Drama | Lux Bhalobashar Shourobher Golpo
Miss Match | Eid Drama | Lux Bhalobashar Shourobher Golpo
Published: 2017/09/07
Channel: LUX Bangladesh
Lux - It
Lux - It's Like Summer [Featuring Dance Mom's Abby Lee Dance team] (OFFICIAL VIDEO)
Published: 2012/01/23
Channel: LUXofficial
The Light Within | Elementalist Lux - League of Legends
The Light Within | Elementalist Lux - League of Legends
Published: 2016/11/28
Channel: League of Legends
Son Lux - Easy
Son Lux - Easy
Published: 2013/10/16
Channel: Music Ward
[ Bình Luận LMHT ] Sức Mạnh Kinh Khủng Của Lux Full Dame | Quất Quadrakill Nhẹ Nhàng
[ Bình Luận LMHT ] Sức Mạnh Kinh Khủng Của Lux Full Dame | Quất Quadrakill Nhẹ Nhàng
Published: 2017/08/28
Channel: Bi Usagii
"AMAZING LUX 5 MAN ULT HEAD SHOT" ( League of Legends - LoL Best Moments )
"AMAZING LUX 5 MAN ULT HEAD SHOT" ( League of Legends - LoL Best Moments )
Published: 2017/05/20
Channel: SoloTop - LOL
New Lux Perfumed Collection
New Lux Perfumed Collection
Published: 2017/07/12
Channel: Lux Pakistan YouTube
1 ULTİ İLE TEK ATAN LUX!! HEXTECH SİLAHKILIÇLI BUİLD! (Üst Koridor Lux)
1 ULTİ İLE TEK ATAN LUX!! HEXTECH SİLAHKILIÇLI BUİLD! (Üst Koridor Lux)
Published: 2017/08/18
Channel: Çoban Espor
❀ELEMENTALIST LUX  - first impression ❀
❀ELEMENTALIST LUX - first impression ❀
Published: 2016/12/02
Channel: LilyPichu
Lux Montage 18 - Lux One Shot
Lux Montage 18 - Lux One Shot
Published: 2017/09/21
Channel: Razmik LOL
Đây chính là sức mạnh THẦN THÁNH của LUX - LMHT (LUX MONTAGE)
Đây chính là sức mạnh THẦN THÁNH của LUX - LMHT (LUX MONTAGE)
Published: 2017/04/28
Channel: LMHT - LOL - Skin - Montage
Lux Montage #17 - Lux 1V5 Pentakill
Lux Montage #17 - Lux 1V5 Pentakill
Published: 2017/09/08
Channel: Razmik LOL
U DUBB PRESENTS LOADED LUX VS HOLLOW DA DON (full HD)
U DUBB PRESENTS LOADED LUX VS HOLLOW DA DON (full HD)
Published: 2014/07/13
Channel: NonFiction Radio
LUX presents We Are More featuring Lira, Nhlanhla Nciza & Moneoa
LUX presents We Are More featuring Lira, Nhlanhla Nciza & Moneoa
Published: 2017/06/14
Channel: LUX South Africa
Lux Montage #9 - Lux Best Plays S7 - [ONE SHOT !!! ] - League of Legends
Lux Montage #9 - Lux Best Plays S7 - [ONE SHOT !!! ] - League of Legends
Published: 2017/09/03
Channel: LolGa Spotlight
Lux Montage #8 - Best Lux plays S7 - ONE SHOT ?
Lux Montage #8 - Best Lux plays S7 - ONE SHOT ?
Published: 2017/07/14
Channel: LolGa Spotlight
Orianna Mid Full AP Tốc Độ Đánh | LUX Bốc Hơi Trong 1s | Trâu Best Udyr
Orianna Mid Full AP Tốc Độ Đánh | LUX Bốc Hơi Trong 1s | Trâu Best Udyr
Published: 2017/09/22
Channel: Trâu Cày Thuê
TEK ATAN LUX!! FULL KOMBO = 2 SKOR!! ELMAS SERİLERİ (2/5)
TEK ATAN LUX!! FULL KOMBO = 2 SKOR!! ELMAS SERİLERİ (2/5)
Published: 2017/04/09
Channel: Oyunbros Zamanı
Presenting the 16th Lux Style Awards (Part 2)
Presenting the 16th Lux Style Awards (Part 2)
Published: 2017/05/20
Channel: Lux Pakistan YouTube
Chết cười với thánh chơi Lux chém gió kinh vãi chưởng | Bình luận hài LMHT
Chết cười với thánh chơi Lux chém gió kinh vãi chưởng | Bình luận hài LMHT
Published: 2017/07/02
Channel: Thiên An
Lux montage #5  - Best Lux Plays season 7 - Fast one shot combo | League of Legends
Lux montage #5 - Best Lux Plays season 7 - Fast one shot combo | League of Legends
Published: 2017/05/26
Channel: LolGa Spotlight
LUX Channel i Super Star 2014 Grand Finale Result
LUX Channel i Super Star 2014 Grand Finale Result
Published: 2014/11/08
Channel: Bangladesh News 365
LUX Channel i Super Star 2014 Episode 7 HD (Full Episode)
LUX Channel i Super Star 2014 Episode 7 HD (Full Episode)
Published: 2014/09/12
Channel: LUX Bangladesh
Lux Special Interactions
Lux Special Interactions
Published: 2017/03/09
Channel: SkinSpotlights
MEET MY NEW GIRLFRIEND!!
MEET MY NEW GIRLFRIEND!!
Published: 2017/09/22
Channel: Nej D'Lux
JANKO PREVARANT? - DISS - SIMI,LUX,GLISA,BITEMYLIFE - PRVI BH YT SKUP!
JANKO PREVARANT? - DISS - SIMI,LUX,GLISA,BITEMYLIFE - PRVI BH YT SKUP!
Published: 2017/09/13
Channel: BalkanAlert
Spce CadeX - Fire (Ft. Lux)
Spce CadeX - Fire (Ft. Lux)
Published: 2017/09/22
Channel: Nightblue Music
¡¡SOY UNA LUX MAGISTRAL, TO THE LCS!! • LUX MID S7 7.18 2017 • KERIOS
¡¡SOY UNA LUX MAGISTRAL, TO THE LCS!! • LUX MID S7 7.18 2017 • KERIOS
Published: 2017/09/21
Channel: Kerios
Pokimane - GIVE ME LUX
Pokimane - GIVE ME LUX
Published: 2016/11/13
Channel: Pokimane
Son Lux - "Easy" (Official Video)
Son Lux - "Easy" (Official Video)
Published: 2014/10/08
Channel: Joyful Noise Recordings
Lux: Binding Light | League Animation Workshop
Lux: Binding Light | League Animation Workshop
Published: 2017/05/19
Channel: League of Legends
Elementalist Lux (Ultimate Skin!) Skin Spotlight - Pre-Release - League of Legends
Elementalist Lux (Ultimate Skin!) Skin Spotlight - Pre-Release - League of Legends
Published: 2016/11/09
Channel: SkinSpotlights
Lux URF Dễ Dàng Pentakill | Thảm Sát 33 Mạng | Trâu Best Udyr
Lux URF Dễ Dàng Pentakill | Thảm Sát 33 Mạng | Trâu Best Udyr
Published: 2017/08/15
Channel: Trâu Cày Thuê
Master of ALL Elements | Lux Support - Aphromoo
Master of ALL Elements | Lux Support - Aphromoo
Published: 2017/05/06
Channel: Aphromoo
LUX MID GAMEPLAY - PICK SAFE E MUITO FORTE - League of Legends - Fiv5 gameplay
LUX MID GAMEPLAY - PICK SAFE E MUITO FORTE - League of Legends - Fiv5 gameplay
Published: 2017/03/20
Channel: Fiv5
MIDI LIDI: LUX
MIDI LIDI: LUX
Published: 2016/05/02
Channel: MIDI LIDI
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
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A lux meter for measuring illuminances in work places

The lux (symbol: lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area.[1] It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form.[2]

Explanation[edit]

Illuminance[edit]

Illuminance is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to area when the luminous flux is held constant.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m2 = 1 cd·sr/m2.

A flux of 1000 lumens, concentrated into an area of 1 square metre, lights up that square metre with an illuminance of 1000 lux. However, the same 1000 lumens, spread out over 10 square metres, produces a dimmer illuminance of only 100 lux.

Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1000 lux.

Here are some examples of the illuminance provided under various conditions:

Illuminance (lux) Surfaces illuminated by
0.0001 Moonless, overcast night sky (starlight)[3]
0.002 Moonless clear night sky with airglow[3]
0.05–0.36 Full moon on a clear night[4]
3.4 Dark limit of civil twilight under a clear sky[5]
20–50 Public areas with dark surroundings[6]
50 Family living room lights (Australia, 1998)[7]
80 Office building hallway/toilet lighting[8][9]
100 Very dark overcast day[3]
320–500 Office lighting[7][10][11][12]
400 Sunrise or sunset on a clear day.
1000 Overcast day;[3] typical TV studio lighting
10,000–25,000 Full daylight (not direct sun)[3]
32,000–100,000 Direct sunlight

The illuminance provided by a light source on a surface perpendicular to the direction to the source is a measure of the strength of that source as perceived from that location. For instance, a star of apparent magnitude 0 provides 2.08 microlux at the Earth's surface.[13] A barely perceptible magnitude-6 star provides 8 nanolux.[14] The unobscured Sun provides an illumination of up to 100 kilolux on the Earth's surface, the exact value depending on time of year and atmospheric conditions. This direct normal illuminance is related to the solar illuminance constant Esc, equal to 128000 lux (see Sunlight).

The illuminance on a surface depends on how the surface is tilted with respect to the source. For example, a pocket flashlight aimed at a wall will produce a given level of illumination if aimed perpendicular to the wall, but if the flashlight is aimed at increasing angles to the perpendicular (maintaining the same distance), the illuminated spot becomes larger and so is less highly illuminated. When a surface is tilted at an angle to a source, the illumination provided on the surface is reduced because the tilted surface subtends a smaller solid angle from the source, and therefore it receives less light. For a point source, the illumination on the tilted surface is reduced by a factor equal to the cosine of the angle between a ray coming from the source and the normal to the surface.[15] In practical lighting problems, given information on the way light is emitted from each source and the distance and geometry of the lighted area, a numerical calculation can be made of the illumination on a surface by adding the contributions of every point on every light source.

Luminous emittance[edit]

The lux is also a measure of luminous emittance, the number of lumens given off by a surface per square metre, regardless of how that light is distributed in terms of the directions in which it is emitted. It differs from the luminance (measured in candela per square metre or "nits"), which does depend on the angular distribution of the emission. A perfectly white surface with one lux falling on it will emit one lux.

Relationship between illuminance and irradiance[edit]

Like all photometric units, the lux has a corresponding "radiometric" unit. The difference between any photometric unit and its corresponding radiometric unit is that radiometric units are based on physical power, with all wavelengths being weighted equally, while photometric units take into account the fact that the human eye's image-forming visual system is more sensitive to some wavelengths than others, and accordingly every wavelength is given a different weight. The weighting factor is known as the luminosity function.

The lux is one lumen per square metre (lm/m2), and the corresponding radiometric unit, which measures irradiance, is the watt per square metre (W/m2). There is no single conversion factor between lx and W/m2; there is a different conversion factor for every wavelength, and it is not possible to make a conversion unless one knows the spectral composition of the light.

The peak of the luminosity function is at 555 nm (green); the eye's image-forming visual system is more sensitive to light of this wavelength than any other. For monochromatic light of this wavelength, the amount of illuminance for a given amount of irradiance is maximum: 683.002 lux per 1 W/m2; the irradiance needed to make 1 lux at this wavelength is about 1.464 mW/m2. Other wavelengths of visible light produce fewer lux per watt-per-meter-squared. The luminosity function falls to zero for wavelengths outside the visible spectrum.

For a light source with mixed wavelengths, the number of lumens per watt can be calculated by means of the luminosity function. In order to appear reasonably "white", a light source cannot consist solely of the green light to which the eye's image-forming visual photoreceptors are most sensitive, but must include a generous mixture of red and blue wavelengths, to which they are much less sensitive.

This means that white (or whitish) light sources produce far fewer lumens per watt than the theoretical maximum of 683.002 lm/W. The ratio between the actual number of lumens per watt and the theoretical maximum is expressed as a percentage known as the luminous efficiency. For example, a typical incandescent light bulb has a luminous efficiency of only about 2%.

In reality, individual eyes vary slightly in their luminosity functions. However, photometric units are precisely defined and precisely measurable. They are based on an agreed-upon standard luminosity function based on measurements of the spectral characteristics of image-forming visual photoreception in many individual human eyes.

Use in video-camera specifications[edit]

Specifications for video cameras such as camcorders and surveillance cameras often include a minimal illuminance level in lux at which the camera will record a satisfactory image.[citation needed] A camera with good low-light capability will have a lower lux rating. Still cameras do not use such a specification, since longer exposure times can generally be used to make pictures at very low illuminance levels, as opposed to the case in video cameras, where a maximal exposure time is generally set by the frame rate.

Non-SI units of illuminance[edit]

The corresponding unit in English and American traditional units is the foot-candle. One foot candle is about 10.764 lux. Since one foot-candle is the illuminance cast on a surface by a one-candela source one foot away, a lux could be thought of as a "metre-candle", although this term is discouraged because it does not conform to SI standards for unit names.

One phot (ph) equals 10 kilolux.

One nox (nx) equals 1 millilux.

In astronomy, apparent magnitude is a measure of the illuminance of a star on the Earth's atmosphere. A star with apparent magnitude 0 is 2.54 microlux outside the earth's atmosphere, and 82% of that (2.08 microlux) under clear skies.[13] A magnitude 6 star (just barely visible under good conditions) would be 8.3 nanolux. A standard candle (one candela) a kilometre away would provide an illuminance of 1 microlux—about the same as a magnitude 1 star.

Legacy Unicode symbol[edit]

Unicode has a symbol for "lx": (㏓). It is a legacy code to accommodate old code pages in some Asian languages. Use of this code is not recommended.

SI photometry units[edit]

SI photometry quantities
Quantity Unit Dimension Notes
Name Symbol[nb 1] Name Symbol Symbol
Luminous energy Qv [nb 2] lumen second lm⋅s TJ [nb 3] Units are sometimes called talbots.
Luminous flux / luminous power Φv [nb 2] lumen (= cd⋅sr) lm J [nb 3] Luminous energy per unit time.
Luminous intensity Iv candela (= lm/sr) cd J [nb 3] Luminous flux per unit solid angle.
Luminance Lv candela per square metre cd/m2 L−2J Luminous flux per unit solid angle per unit projected source area. Units are sometimes called nits.
Illuminance Ev lux (= lm/m2) lx L−2J Luminous flux incident on a surface.
Luminous exitance / luminous emittance Mv lux lx L−2J Luminous flux emitted from a surface.
Luminous exposure Hv lux second lx⋅s L−2TJ
Luminous energy density ωv lumen second per cubic metre lm⋅s⋅m−3 L−3TJ
Luminous efficacy η [nb 2] lumen per watt lm/W M−1L−2T3J Ratio of luminous flux to radiant flux or power consumption, depending on context.
Luminous efficiency / luminous coefficient V 1
See also: SI · Photometry · Radiometry
  1. ^ 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
  2. ^ a b c Alternative symbols sometimes seen: W for luminous energy, P or F for luminous flux, and ρ or K for luminous efficacy.
  3. ^ a b c "J" here is the symbol for the dimension of luminous intensity, not the symbol for the unit joules.

See also[edit]

Notes and references[edit]

  1. ^ SI Derived Units, National Institute of Standards and Technology.
  2. ^ NIST Guide to SI Units. Chapter 9 – Rules and Style Conventions for Spelling Unit Names, National Institute of Standards and Technology.
  3. ^ a b c d e Schlyter, Paul (1997–2009). "Radiometry and photometry in astronomy". 
  4. ^ Kyba, Christopher C M; Mohar, Andrej; Posch, Thomas (1 February 2017). "How bright is moonlight?". Astronomy & Geophysics. 58 (1): 1.31–1.32. doi:10.1093/astrogeo/atx025. 
  5. ^ "Electro-Optics Handbook" (pdf). photonis.com. p. 63. Retrieved 2012-04-02. 
  6. ^ "NOAO Commen and Recommended Light Levels Indoor" (PDF). 
  7. ^ a b Pears, Alan (June 1998). "Chapter 7: Appliance technologies and scope for emission reduction". Strategic Study of Household Energy and Greenhouse Issues (PDF). Sustainable Solutions Pty Ltd. Department of Industry and Science, Commonwealth of Australia. p. 61. Archived from the original (pdf) on 2 March 2011. Retrieved 2008-06-26. 
  8. ^ Australian Greenhouse Office (May 2005). "Chapter 5: Assessing lighting savings". Working Energy Resource and Training Kit: Lighting. Archived from the original on 2007-04-15. Retrieved 2007-03-17. 
  9. ^ "Low-Light Performance Calculator". 
  10. ^ "How to use a lux meter (Australian recommendation)" (PDF). Sustainability Victoria (sustainability.vic.gov.au). April 2010. Archived from the original (pdf) on 7 July 2011.  External link in |publisher= (help)
  11. ^ "Illumination. - 1926.56". Regulations (Standards - 29 CFR). Occupational Safety and Health Administration, US Dept. of Labor. Archived from the original on 8 May 2009. 
  12. ^ European law UNI EN 12464
  13. ^ a b Schlyter, Section 7.
  14. ^ Schlyter, Section 14.
  15. ^ Jack L. Lindsey, Applied Illumination Engineering, The Fairmont Press, Inc., 1997 ISBN 0881732125 page 218

External links[edit]

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