How is Light Output/lumen/etc. Measured?

OneHitDone

OneHitDone

Well-Known Member
Curious if anyone has any insight on how manufactures get there lumen and other output numbers with different light sources.
I know this is the LED forum but I think it is relative to the whole lighting discussion to understand the whole field of light sources.
With a unidirectional led it would seem a simple task just point the diode at the sensor, but with something like an hps lamp that emits light 360°, how do they arrive at the rated outputs?
 
OneHitDone

OneHitDone

Well-Known Member
SupraSPL said:
The most accurate way to measure PPF (bulb output) for any light source would be to use an integrating sphere and the best way to measure PPFD (photon density in the canopy) would be with a calibrated spectroradiometer and a 4X4 grid.



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How does an integrated sphere like that work with something like a big ass inda-gro induction lamp or a long fluorescent tube?

Has anyone done an accurate spectroradiometer on the inda-gro 420/pontoon combo?
 
SupraSPL

SupraSPL

Well-Known Member
Good point they would have to use a large one. I assume they must have tested the 8 foot long fluoro tubes often used in greeenhouses, or maybe they just extrapolate from the 4 footers


I attempted to calculate an estimated PPFD for Indagrow as you may recall:

Indagrow 420 in a 4X4 with pontoon:
227+35.9 = 263 PPFD averaged

Indagrow 420 in a 3X3 with pontoon:
468 PPFD averaged

Would be interesting to see if spectroradiometer measurements agree.
 
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churchhaze

Well-Known Member
OneHitDone said:
Curious if anyone has any insight on how manufactures get there lumen and other output numbers with different light sources.
I know this is the LED forum but I think it is relative to the whole lighting discussion to understand the whole field of light sources.
With a unidirectional led it would seem a simple task just point the diode at the sensor, but with something like an hps lamp that emits light 360°, how do they arrive at the rated outputs?
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To take what Supra said a bit further, lumens is an arbitrary unit that's not actually a measure of power nor is it a measure of photon flux. It doesn't actually measure anything tangible.

https://en.wikipedia.org/wiki/Luminous_efficacy

What's important is PPF (umol/s) and radiometric power (watts). It's best to ignore lumen rating all together for light sources with different spectral distributions. The only thing it's good for is confusing the hell out of people...

People saying "watts don't matter" are wrong. Radiometric watts between 400-700nm matters (watts PAR). A lot people say radiometric watts is misleading, and that plants only care about the quantity of photons, but that argument is also very misleading as using all 660nm lamp with very high photon flux will not be better than a wide spectrum lamp with higher efficiency, but lower umol/J.
 
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churchhaze

Well-Known Member
OneHitDone said:
Duh, I should have thought to look there bongsmilie

I guess the next question would be 533 uMol/w/s over what size area?
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It actually says 533 umol/s. This is a measure of PPF, not PPFD, so the area it covers is irrelvant. PPF is the total photon flux output.

PPF (total output) is a more useful number for measuring the output of a light, while PPFD (density) is more useful for light distribution. A lot of lighting companies will have high PPFD in the center of output distribution, but will quickly taper off. This is just a trick. PPF of a lamp matters, while PPFD doesn't so much.
 
OneHitDone

OneHitDone

Well-Known Member
churchhaze said:
It actually says 533 umol/s. This is a measure of PPF, not PPFD, so the area it covers is irrelvant. PPF is the total photon flux output.

PPF (total output) is a more useful number for measuring the output of a light, while PPFD is more useful for light spread. A lot of lighting companies will have high PPFD in the center of output distribution, but will quickly taper off. This is just a trick. Only the total PPF matters.
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I would sure like to see a legit sensor grid reading on the Inda-gro 420/pontoon.
Everyone is saying spectroradiometer but I thought it was a quantum sensor that measures plant usable light?
 
E

Eraserhead

Well-Known Member
A quantum meter costs $300 or less. A spectroradiometer costs $4000+.
OneHitDone said:
I would sure like to see a legit sensor grid reading on the Inda-gro 420/pontoon.
Everyone is saying spectroradiometer but I thought it was a quantum sensor that measures plant usable light?
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The spectro will get you more accurate readings, from the entire spectrum which a quantum meter can not do.

My spectro reads from 350nm to 1150nm.

A quantum meter, or PAR meter as a lot of people call them, reads 440nm-645nm, some a little wider, but nothing significant.

The Idna Grow does not in anyway whatsoever compare to the better LEDs. The numbers just aren't there and no one, no where are getting results with them, if so, where are they? I'd like to see them. Links links links...
 
AquariusPanta

AquariusPanta

Well-Known Member
Eraserhead said:
A quantum meter costs $300 or less. A spectroradiometer costs $4000+.

The spectro will get you more accurate readings, from the entire spectrum which a quantum meter can not do.

My spectro reads from 350nm to 1150nm.

A quantum meter, or PAR meter as a lot of people call them, reads 440nm-645nm, some a little wider, but nothing significant.

The Idna Grow does not in anyway whatsoever compare to the better LEDs. The numbers just aren't there and no one, no where are getting results with them, if so, where are they? I'd like to see them. Links links links...
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Luckily Apogee will calculate a power factor for wavelengths outside their quantum meter's limits (such as 400-800nm), but only by using the data from the typical color spectrum graphs for a given COB, which requires finding the percentages for each of the individual wavelengths on the graph (not for the lighthearted).

I know of this, thanks to @Greengenes707 and @alesh.
 
alesh

alesh

Well-Known Member
AquariusPanta said:
Luckily Apogee will calculate a power factor for wavelengths outside their quantum meter's limits (such as 400-800nm), but only by using the data from the typical color spectrum graphs for a given COB, which requires finding the percentages for each of the individual wavelengths on the graph (not for the lighthearted).

I know of this, thanks to @Greengenes707 and @alesh.
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The disadvantage is that the measurement will be inaccurate if you try it with another CCT/CRI combination or even different technology.So you have to know what you're measuring.
 
SupraSPL

SupraSPL

Well-Known Member
AquariusPanta said:
Luckily Apogee will calculate a power factor for wavelengths outside their quantum meter's limits (such as 400-800nm), but only by using the data from the typical color spectrum graphs for a given COB, which requires finding the percentages for each of the individual wavelengths on the graph (not for the lighthearted).
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That is a definitely a step in the right direction, but using the correction factor, the measurement is subject to the same math as our PPFD calculations. In other words, even with the PAR meter we are still guessing. It would be great for relative comparisons, checking light distribution, temp droop and bulb depreciation, but so are $15 lux meters. As Alesh pointed out, not great for absolute measurements or comparing lights of different CCT.

Not saying it is useless but I'm not sure it is any more useful than a cheap lux meter.
 
salmonetin

salmonetin

Well-Known Member
...very nice "toy" EH...

http://www.stellarnet.us/products_spectrometers_BlueWave.htm

http://www.apogeeinstruments.com/visible-to-near-infrared-range-spectroradiometer-ps-100/?page_context=category&faceted_search=0



....i miss a side to side ...your spd curves and the actual spd curves on datasheets for the new veros 2 models... ...to compare data results... ...lot of side to side comparations you can do... maybe share a few spd curves with the poor ones ...we can believe in the spd curves on the datasheets?...

...please share your spd curves for the new cobs... i know you use others led models ....i dont try revels yours data led models... ...my interest are the new cobs top models... we can believe in the actual spd curves on the datasheets?

...and pardon my bad english write...

pd...dreaming again...:eyesmoke:

:peace:

saludos
 
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alesh

alesh

Well-Known Member
Greengenes707

Greengenes707

Well-Known Member
SupraSPL said:
That is a definitely a step in the right direction, but using the correction factor, the measurement is subject to the same math as our PPFD calculations. In other words, even with the PAR meter we are still guessing. It would be great for relative comparisons, checking light distribution, temp droop and bulb depreciation, but so are $15 lux meters. As Alesh pointed out, not great for absolute measurements or comparing lights of different CCT.

Not saying it is useless but I'm not sure it is any more useful than a cheap lux meter.
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The theory of error is correct. But in reality is negligible. If anything, it's on the safe/low side.

With white LEDs Lux is closer to relevant. But why...which Would you publish for others to review for plant lighting purposes(assume spectrometer is out). It's a quantum process...use a quantum meter...to me that is a more solid theory than not using one because of a less than 10% error at worst based on theory.
 
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