what is the difference between luminous flux and lumens
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Hello David,The answer is sort of technical, so bare with me. The lumen is the derived unit of luminous flux. Luminous flux is a measure of the total "amount" of visible light (as measured in the green light wavelength spectrum) emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter.Check out Wiikipedia for a more complete answer.Thanks, Glen from CampingStuff Hello David,The answer is sort of technical, so bare with me. The lumen is the derived unit of luminous flux. Luminous flux is a measure of the total "amount" of visible light (as measured in the green light wavelength spectrum) emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are... » Read More Hello David,The answer is sort of technical, so bare with me. The lumen is the derived unit of luminous flux. Luminous flux is a measure of the total "amount" of visible light (as measured in the green light wavelength spectrum) emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter.Check out Wiikipedia for a more complete answer.Thanks, Glen from CampingStuff « Show Less
1101644
Hello David, The answer is sort of technical, so bare with me. The lumen is the derived unit of luminous flux. Luminous flux is a measure of the total "amount" of visible light (as measured in the green light wavelength spectrum) emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter. Check out Wiikipedia for a more complete answer. Thanks, Glen from CampingStuff
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The package I have is labeled 780 lumens. I see no mention of luminus flux.
8338
Not sure about lumens, but I can say that the lights are bright and I am very happy with them. I have 6 rock pillars in the front of my house and they look beautiful.
896139
LED luminosity is directly proportional to voltage but 100+ lm/watt is stretching things, even for the best LED arrays, which this is not. Lumen output is probably no more than 75 lm/watt and that would be at the maximum rated voltage.
546078
This didn't work for my purpose so I don't know about the lumens. It did not clip on the art work as I'd planned.
1921746
There is no documentation as to the brightness as to the brightness of each lamp, however the nightlight puts out 2 to 3 times as much as an incandescence night light and the flashlight does not focus the light in a tight beam but illuminates as much as 2 D cell older flashlight. This light is much whiter than the older lamps and it does a good job. The flashlight will come on day or night if there is a loss of power or is unplugged. I am very satisfied with my two units.
564630
The brightness is great for my jewelry projects. I checked the company website and they don't list lumens in the specs. They do have a way to inquire about the product on this page: http://eles.en.alibaba.com/product/410085674-209355092/8069LED_Magnifying_Lamp_Working_lamp_antistatic_magnifier.html
643168
Hello,we use the Brightest 3528 SMD LEDs for these,Actual working luminous flux about 420~460Lumens,thanks!
777461
Lumens is a measure of brightness and useful when measuring white light from traditional light bulbs but not a very useful metric for LEDs. LED grow lights maximize photosynthesis, not brightness. For example, the red color is very dim compared to the other colors of the spectra, but essential for photosynthesis.
2008199
Not sure about the exact lumens, but it's very bright and visible during the daytime. The unique indicator pattern is very attention grabbing.
2118995
This is a special daylight bulb, neither CF nor LED. I think it is some type of fluorescent. I don't know about lumens. It is nice and bright, very good for needlework.
1178200
I do not have any way to measure lumens but, you are correct, these lights are very bright, especially when focused to the narrow beam.
2228476
(1) KELVIN = temperature of a lamp (5100K plus is considered "daylight"). (2) LUMEN = unit measuring light output of a lamp. (3) CRI = Color Rendition Index measures the true color of an object in the emitted light of a lamp and is of particular importance in film making, photograhic and television applications. I have no idea why this information is hidden.
607664
Also not sure about the lumens, it's enough to read if placed within 20 cm of the text. Excellent light and brightness for pointing at a wall and getting some indirect light. Perfect for bathroom use when you wake up in the middle of the night and don't feel like turning on a ton of bright lights and you think night lights are annoying / wasteful.
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It should be noted that "lumen" can mean many things depending on how you obtain a lumen measurement. At one foot away with the "zoom" at max spread the light produced 4800~4900 lux which is about 450 lumens/sq ft. Though when focus to a point the light produced over 90,000 lux which is about 8,300 lumens/sq ft. Unless you can find definitive data that explains the lumen of this light (or any other light in existence) the advertised brightness of a flashlight is meaningless. It's would be better to look up the datasheet for the Cree XML emitter and search for visual examples of the light (using quality 3.7V 18650 Li-Ion bats of course).
2211811
I cannot answer in Lumens but I can tell you this light is not nearly as bright as any of my other LED flashlights. I am disappointed by it every time I use it.
1604156
I don't know the lums. I use it when I walk my dogs very early in the morning and the light is plenty bright enough. Primarily purchased for the safety features.