LED light intensity

wietefras said:

The fact is that average light levels at any height are the same whether you use 1, 4, 8 or a million light sources. As long as the total initial amount of light is the same. So it is immediately clear that your "findings" are nonsense. The only reason you get those "findings" is because your drawings are incomplete.

The only thing that actually changes with more light sources is the light distribution. The same amount of light gets distributed more uniformly. That's all.

Although that has a knock on effect that you can have the lights closer to the canopy. Which reduces wall losses and therefore improves "penetration". Plus the angles are better.

:edit:
Below a proper simulation of 8, 3 and 1 light source. The chart starts from the point where proper uniformity is achieved (and therefore where the canopy would be). The depth of the chart is 40cm.

Red is max intensity and green is least:
View attachment 4126936
Same relative "penetration" for 8, 3 or 1 light source.

Click to expand...

wietefras said:

Leds get more efficient when you lower the wattage. Is that what he was talking about?

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giantsfan24 said:

No I asked if the decrease on PPFD, or photons or whatever, was proportional to the amount of power being supplied to the light. For example if at 200w the PPFD was, say, 950, then at 100w would it be 475 or in other words half. He said that it didn't work like that. I was trying to get out of buying a PAR meter, lol, is why I was asking the question.

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giantsfan24 said:

No I asked if the decrease on PPFD, or photons or whatever, was proportional to the amount of power being supplied to the light. For example if at 200w the PPFD was, say, 950, then at 100w would it be 475 or in other words half. He said that it didn't work like that. I was trying to get out of buying a PAR meter, lol, is why I was asking the question.

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wietefras said:

Then we are talking about the same thing though.

If you cut the power in half then you increase the efficiency by roughly 10%. So in your example you would go from 950 to say 522.5

Again, not something which would mean you need to buy a PAR meter for. Not a big enough difference and these things can be looked up in a datasheet or estimated by a rule of thumb.

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Moflow said:

Have you not downloaded a Lux Meter app?
Keuwlsoft light meter , free download on playstore for instance.
That'll give you a good idea.

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giantsfan24 said:

No I asked if the decrease on PPFD, or photons or whatever, was proportional to the amount of power being supplied to the light. For example if at 200w the PPFD was, say, 950, then at 100w would it be 475 or in other words half. He said that it didn't work like that. I was trying to get out of buying a PAR meter, lol, is why I was asking the question.

Click to expand...

wietefras said:

Take your mosaic drawings and put the same numbers on the side for all three. That's what your drawings should have shown. Perhaps you can try to work out from there what you did wrong.

My charts show only the 1000 to 500umol zone and that the relative depth is the same in all cases. You claimed it was 12", 18" and 21", higher with more light sources. So no, it's not even remotely the same what you claimed.

If anything it's the opposite, because as you stated, the red layer is less deep with more light sources. That's just a uniformity issue though. It's deeper in the middle with one light source, but shallower on the sides. On average the "depth" is the same.

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nfhiggs said:

The fact that you cannot grasp the implication that is obvious in your own image is telling.

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wietefras said:

The fact is that average light levels at any height are the same whether you use 1, 4, 8 or a million light sources. As long as the total initial amount of light is the same. So it is immediately clear that your "findings" are nonsense. The only reason you get those "findings" is because your drawings are incomplete.

The only thing that actually changes with more light sources is the light distribution. The same amount of light gets distributed more uniformly. That's all.

Although that has a knock on effect that you can have the lights closer to the canopy. Which reduces wall losses and therefore improves "penetration". Plus the angles are better.

:edit:
Below a proper simulation of 8, 3 and 1 light source. The chart starts from the point where proper uniformity is achieved (and therefore where the canopy would be). The depth of the chart is 40cm.

Red is max intensity and green is least:
View attachment 4126936
Same relative "penetration" for 8, 3 or 1 light source.

Click to expand...

wietefras said:

Photons aren't thrown further with more watts.

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wietefras said:

Photons aren't thrown further with more watts. They travel infinitely until they are absorbed. Was that supposed to be your point? Did we now arrive at the goal post shifting phase of your "rebuttal"?

You made the same mistake as that pretend researcher. Your drawings indicate that "ISL" applies in a grow tent for the average PPFD. It does not. Not with one light source either. For a single center PPFD measurement yes, but not for the average PPFD.

In a 100% reflective tent of one square meter, what is the average PPFD you get with a 1000PPF light source at 10cm? At 50cm? At 1000cm? It's the exact same average 1000PPFD everywhere. All the way down. That's the first basic mistake of your mosaics. So again, start putting the same number on the side of your mosaics everywhere and try to figure out where you went wrong.

Maybe then you understand that your 8 light source mosaic should show some mosaic pattern at the top 10cm to 15cm and then all the same color below that.

Now what does actually lose you light intensity with height? It's not distance the light travelled, so what then? Wall losses yes.

The only drop-off you see in my charts is caused by uniformity differences and that I actually applied reflections and the resulting wall losses. Wall losses, which also are the same in every chart). It is nothing like your mosaics and there is no difference in relative "depth" whatsoever. None.

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Slinging PAR said:

Ok quit fighting over which ice cream is the best flavor. So long as the end result is that all of the photons you can generate hit the plant then you are doing it right.

Your plants will tell you if you are right or wrong. Not some internet forum. What works for me won't work for you. Why? There are far too many different factors involved and it is impossible to replicate experience. Everyone has to learn at their own rate so they can know what is going on and figure out what works best for them.

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Streetsports said:

Call the person out or keep it to yourself. Passive aggressiveness is sad.my pretend research came from laboratory tests that have been shown more than once. You're the guy telling one person they don't need a par meter while you tell others to use one. If the forums frustrate you then don't log in.

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