Information about Lumen (unit)
For other uses of the word, see .
The lumen (symbol: lm) is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.
Definition
1 lm = 1 cd·sr = 1 lx·m2Explanation
If a light source emits one candela of luminous intensity into a solid angle of one steradian, the total luminous flux emitted into that solid angle is one lumen. Alternatively, an isotropic one-candela light source emits a total luminous flux of exactly
lumens. The lumen can be thought of casually as a measure of the total "amount" of visible light emitted.
A standard 100 watt incandescent light bulb emits approximately 1700 lumens in North America and around 1300 lumens in 220V areas of the world. See luminous efficacy for the specific efficiency of various types of electric light sources.
ANSI lumens
The light output of projectors (including video projectors) is typically measured in lumens. A standardized procedure for testing projectors has been established by the American National Standards Institute, which involves averaging together several measurements taken at different positions.[1] For marketing purposes, the luminous flux of projectors that have been tested according to this procedure may be quoted in "ANSI lumens", to distinguish devices that have been so tested from those tested by other methods. ANSI lumen measurements are in general more accurate than the other measurement techniques used in the projector industry.[2] This allows projectors to be more easily compared on the basis of their brightness specifications.SI photometry units
| Quantity | Symbol | SI unit | Abbr. | Notes |
|---|---|---|---|---|
| Luminous energy | Qv | lumen second | lms | units are sometimes called talbots |
| Luminous flux | F | lumen (= cdsr) | lm | also called luminous power |
| Luminous intensity | Iv | candela (= lm/sr) | cd | an SI base unit |
| Luminance | Lv | candela per square metre | cdm–2 | units are sometimes called nits |
| Illuminance | Ev | lux (= lmm–2) | lx | Used for light on a surface |
| Luminous emittance | Mv | lux (= lmm–2) | lx | Used for light emitted from a surface |
| Luminous efficacy | lumen per watt | lm/W | ratio of luminous flux to radiant flux; maximum possible is 683.002 |
See also
- Brightness
- Lux
- Lm is also the sign for the Malta Lira currency along side the £
References
1. ^ ANSI lumen article. PC Magazine Encyclopedia. Retrieved on 2006-12-20.
2. ^ Projector Guide. CPILive.net (February 2004). Retrieved on 2006-12-20.
2. ^ Projector Guide. CPILive.net (February 2004). Retrieved on 2006-12-20.
Si, si, or SI may refer to (all SI unless otherwise stated):
In language:
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In language:
- One of two Italian words:
- sì (accented) for "yes"
- si
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luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of
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Light is electromagnetic radiation of a wavelength that is visible to the eye (visible light). In a scientific context, the word "light" is sometimes used to refer to the entire electromagnetic spectrum.
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In radiometry, radiant flux or radiant power is the measure of the total power of electromagnetic radiation (including visible light). The power may be the total emitted from a source, or the total landing on a particular surface.
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Eyes are organs of vision that detect light. Different kinds of light-sensitive organs are found in a variety of organisms. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors.
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In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek letter lambda (λ). Examples of wave-like phenonomena are light, water waves, and sound waves.
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candela (symbol: cd) is the SI base unit of luminous intensity (that is, power emitted by a light source in a particular direction, with wavelengths weighted by the luminosity function, a standardized model of the sensitivity of the human eye).
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The steradian (symbol: sr) is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane.
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LUX is the principal centre for the promotion and distribution of experimental film and video works in the UK.
It has one of the largest collections of experimental film and video art and houses works of over 1000 artists.
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It has one of the largest collections of experimental film and video art and houses works of over 1000 artists.
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1 metre =
SI units
1000 mm 0 cm
US customary / Imperial units
0 ft 0 in
The metre or meter[1](symbol: m) is the fundamental unit of length in the International System of Units (SI).SI units
1000 mm 0 cm
US customary / Imperial units
0 ft 0 in
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candela (symbol: cd) is the SI base unit of luminous intensity (that is, power emitted by a light source in a particular direction, with wavelengths weighted by the luminosity function, a standardized model of the sensitivity of the human eye).
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In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction, based on the luminosity function, a standardized model of the sensitivity of the human eye.
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The solid angle, Ω, is the angle that an object subtends at a point. It is a measure of how big that object appears to an observer at that point. For instance, a small object nearby could subtend the same solid angle as a large object far away.
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The steradian (symbol: sr) is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane.
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luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of
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Isotropy (the opposite of anisotropy) is the property of being independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented.
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WATT
City of license Cadillac, Michigan
Broadcast area [1]
Branding NewsTalk 1240
First air date 1945
Frequency 1240 kHz
Format News-Talk-Sports
Power 1,000 watts
Class C
Owner MacDonald Garber Broadcasting
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City of license Cadillac, Michigan
Broadcast area [1]
Branding NewsTalk 1240
First air date 1945
Frequency 1240 kHz
Format News-Talk-Sports
Power 1,000 watts
Class C
Owner MacDonald Garber Broadcasting
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incandescent light bulb (also spelled lightbulb) or incandescent lamp is a source of artificial light that works by incandescence. An electrical current passes through a thin filament, heating it until it produces light.
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Luminous efficacy is a property of light sources, which indicates what portion of the emitted electromagnetic radiation is usable for human vision. It is the ratio of emitted luminous flux to radiant flux.
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Projectors are used for displaying an image on a projection screen or similar surface for the view of an audience.
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- Video projectors
- LCD projector
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video projector takes a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual
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American National Standards Institute or ANSI (IPA pronunciation: [ænsiː]) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes,
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Si, si, or SI may refer to (all SI unless otherwise stated):
In language:
..... Click the link for more information.
In language:
- One of two Italian words:
- sì (accented) for "yes"
- si
..... Click the link for more information.
In photometry, luminous energy is the perceived energy of light. This is sometimes also called the quantity of light.
Luminous energy is not the same as the radiant energy, the corresponding objective physical quantity.
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Luminous energy is not the same as the radiant energy, the corresponding objective physical quantity.
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second (SI symbol: s), sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time.
SI prefixes are frequently combined with the word second to denote subdivisions of the second, e.g.
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SI prefixes are frequently combined with the word second to denote subdivisions of the second, e.g.
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second (SI symbol: s), sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time.
SI prefixes are frequently combined with the word second to denote subdivisions of the second, e.g.
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SI prefixes are frequently combined with the word second to denote subdivisions of the second, e.g.
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In photometry, the talbot (T) is a nonstandard unit of luminous energy, named in honor of the early photographer William Fox Talbot. It is exactly equal to the SI standard unit, the lumen · second:
SI photometry units
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- 1 T = 1 lm · s
SI photometry units
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luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of
..... Click the link for more information.
..... Click the link for more information.
candela (symbol: cd) is the SI base unit of luminous intensity (that is, power emitted by a light source in a particular direction, with wavelengths weighted by the luminosity function, a standardized model of the sensitivity of the human eye).
..... Click the link for more information.
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The steradian (symbol: sr) is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a plane.
..... Click the link for more information.
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