Could someone help me out with Lux/Lumens levels.?
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Could someone help me out with Lux/Lumens levels.?
We would like to compare different light globes in lumens and lux. So I’m trying to convert Watts to Lumens and Lux. PLease HELP.
100w Incandescent globe = ? lumens and ? lux
20w ES Compact Fluro globe = ? Lumens and ? Lux
36w Linear Fluro Tube = ? lumens and ?lux
13w GU10 Compact Fluro = ? Lumens and ? Lux
5w LED = ? Lumens and ? Lux
50w GU10 Halogen = ? Lumens and ? Lux
50w MR16 Halogen = ? Lumens and ? Lux
Or any websites for dummies on converting watts to lux/lumens.You could direct us to would be great. Or is there a formula to do this??
if there just easy converter web site to use to help me maybe that we easier to get my answers.
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Answer by starryskyn
http://en.wikipedia.org/wiki/Lux
One lux is equal to one lumen per square metre, where 4π lumens is the total luminous flux of a light source of one candela of luminous intensity:
1 lx = 1 lm·m-2 = 1 cd·sr·m–2.
As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.
The lux is one lumen/metre2, and the corresponding radiometric unit, which measures irradiance, is the watt/metre2. There is no single conversion factor between lux and watt/metre2; 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 is more sensitive to light of this wavelength than any other. For monochromatic light of this wavelength, the irradiance needed to make one lux is minimum, at 1.464 mW/m2. That is, one obtains 683.002 lux per W/m2 (or lumens per watt) at this wavelength. Other wavelengths of visible light produce fewer lumens per watt. 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 is most sensitive, but must include a generous mixture of red and blue wavelengths to which it is much less sensitive.
This means that white (or whitish) light sources produce far fewer lumens per watt than the theoretical maximum of 683 lumens per watt. 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%
end quote
So bulbs you mention are 638x.02=12.7 lumens/W
then the 100W bulb is about 127 lumens and 127 Lux if it illuminates 1 square meter.
For other types of sources, with spectrum differences, a comparison is a crapshoot.
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