Lux to Lumens?

tanan

New member
A friend of mine bought some LEDs and they seem to have great light.
They are not listed with their lumen rating but my friend has lux meter.But we dont know how to convert lux into lumen for LEDs.
Can anyone help us ?
 
More or less correct, Lux is an SI unit for illuminance, which measures luminous flux per unit of area. Lumens is a unit that measures luminous flux. One lux is one lumen per square meter.

Luminous flux (lumens) basically measures the total amount of light given off by a luminary, while illuminance (lux) measures the intensity of light at a single point.

These are both photometric units, meaning they weigh the spectrum of wavelengths present unequally (basically in an attempt to weight according to what the human eye perceives).
 
That I know but if the LED is giving out 424 lux at 19 inches distance from source.
Then is it good enough? How much lumens it is?
Its a 10K LED
 
That I know but if the LED is giving out 424 lux at 19 inches distance from source.
Then is it good enough? How much lumens it is?
Its a 10K LED

Did you read what was posted above? You can't just convert lux to lumens. You need more information. 1 lux is equal to 1 lumen per square meter.

Its that "per square meter" thing you need to resolve.
 
For example, take the 494 lumens over 1 square meter. That would be 494 lux. Spread that same 494 lumens light out over 10 square meters, and it's 49.4 lux.

At least that's the way the unit math works.
 
David, wouldn't they be better off to be finding the PAR value for the light and comparing that to the old light? Even I'm not 100% sure about that.
 
David, wouldn't they be better off to be finding the PAR value for the light and comparing that to the old light? Even I'm not 100% sure about that.

Surely. That's the way I understand it.

I'm really going to defer to DWZM on that.
 
Lux or lumens, it doesn't matter, neither has anything to do with photosynthesis and neither is a useful measure of light intensity for our purposes.

As mentioned they are measures of perceived light intensity, not actual light intensity. They can underestimate blue light, by 2000% or more, compared to yellow-green light, which is problematic as our aquariums tend to use blue light...

In practice, it ends up as mostly a measure of yellow-green light, which is not what we want. I'd strongly recommend looking around to see if someone will lend you a PAR meter...
 
I would love to get my hands on a PAR meter.
And I did read that David.And I already know the 1lux =1 lumen/meter square.
And since there is this lux=lumen thing I thought they would be inter convertable with proper data.
Lets say I take readings of the LED in 1 square meter and then take the average of the readings.Would that give me the Lumens?
And like Sanjay Joshi says every light is photon we just need to find the ones that could be usable.
Thanks everyone for answering.I guess I would rather ask my friend to make a small fixture and check its results.
 
See, it's kind of like asking this.

It's 135 miles to Memphis. How many miles per gallon will I get?

If you are trying to compare LEDs, then you can just ignore those numbers. They aren't telling you what you need to know anyway. Check out other people's fixtures and par values.
 
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