Dothraki said:

Awesome! That’s exactly what I was wondering with distance & intensity. Soo to make sure I’m understanding correctly... @dbrzz is 850 PAR at 24”, so if he dropped down to 12” he’d be at 3400 PAR and at 18” 1700, etc. is that correct?

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I originally stated that it may be correct but in subsequent conversations with your original correspondent have come to the conclusion that I was wrong in stating that the PPFD was a factor that was governed by the ISL. PPFD is a measure of the PAR values (which refers to the frequency ranges being emitted by the light in question) I have a Doctor Lux-meter that I used to test my lights at various distances and although I have tossed those results now that I am thinking back on them they were more linear in relation to dropoff as distance increases. I was confused by thinking that PPFD was the measure of the total amount of photons coming off the LEDs, so I must apologize to you for misleading you on your original concern.

growsince79 said:

View attachment 1184018View attachment 1184019
Incorrectly using the inverse square formala to calculate won't get you the correct numbers. With a HPS, if I move from 18" to 12" the center value should double. Not so with qbs and panels.

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tucume66 said:

I originally stated that it may be correct but in subsequent conversations with your original correspondent have come to the conclusion that I was wrong in stating that the PPFD was a factor that was governed by the ISL. PPFD is a measure of the PAR values (which refers to the frequency ranges being emitted by the light in question) I have a Doctor Lux-meter that I used to test my lights at various distances and although I have tossed those results now that I am thinking back on them they were more linear in relation to dropoff as distance increases. I was confused by thinking that PPFD was the measure of the total amount of photons coming off the LEDs, so I must apologize to you for misleading you on your original concern.

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But wouldn’t it still apply? Since each point was .....oh wait...so since the other led lights bleed through to the marker...it’ll read those differently based on how high, and the angle they......oh fuckit. I’ll just try the manufacturers recommended heights until I can fork up the $500 for the proper meter lol.

Here’s what they recommend...

Dothraki said:

But wouldn’t it still apply? Since each point was .....oh wait...so since the other led lights bleed through to the marker...it’ll read those differently based on how high, and the angle they......oh fuckit. I’ll just try the manufacturers recommended heights until I can fork up the $500 for the proper meter lol.

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A free meter works fine.

I would think the manufacturers published chart is very accurate. No name companies that you have never heard of and who advertise for an extremely low price might be suspect, but a name brand simply has no incentive to misrepresent that chart. It might result in a single sale, but would sour that customer for future purchases. SpiderFarmer is reputable and supports the forum. I had the same doubts initially, and I bought a PAR meter (Highly recommend BTW). I was able to determine that published charts exactly matched my readings (Disclaimer: other manufacturers, not SpiderFarmer). A PAR meter is relatively cheap and is invaluable in setting height/dimming.

Personally, I set my lights up high (approx 3-4') and adjust the dimmers for the PAR that I want. Why do that when you could use less energy with the lamps closer to the plant? Penetration of the canopy and a less drastic fall off of PAR level from the top to the bottom of the plant. The inverse square law, as pointed out by @tucume66, accurately predicts the level of fall off of intensity. So a light that is further away will 1) require more intensity, and 2) have less fall off than a light that is closer to to the plant.

That is why a light that outputs 1200 is useful even though you only need 600-700. In the outdoors, there is zero detectable fall off from the top of the plant to the bottom. That is because the sun is super bright and super far away (inverse square law).

Running lights at a brighter setting also means that you have to have better airflow to keep things cool, so make sure that you have the cooling capacity if you use this method.

I thought PPFD data are given by the manufactures as an average or detailed graphics for the intended area and distance.
Now seeing above they recommend the hanging high by the temperature.
Marketing at its best...

What matters ? Yield or efficency, or both ?
How much money do you have to invest ?

Optimizing the grow enviroment is more important to me than buying led lights with, for example 1800 PPFD.
If preparing a Grow tent , first step is trying to get a nearly uniform illumination of the grow space.
And the tent size shows if it is better with 1 big Led or 3 smaller one.

But everybody has different demands, so there are many ways to come to a good result ...
Important is that you feel happy with your grow and don`t spend too much money.

Kapal said:

I thought PPFD data are given by the manufactures as an average or detailed graphics for the intended area and distance.
Now seeing above they recommend the hanging high by the temperature.
Marketing at its best...

What matters ? Yield or efficency, or both ?
How much money do you have to invest ?

Optimizing the grow enviroment is more important to me than buying led lights with, for example 1800 PPFD.
If preparing a Grow tent , first step is trying to get a nearly uniform illumination of the grow space.
And the tent size shows if it is better with 1 big Led or 3 smaller one.

But everybody has different demands, so there are many ways to come to a good result ...
Important is that you feel happy with your grow and don`t spend too much money.

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Yeah I’m not sure why it says “recommended heights based on 82f temperature. That’s odd to me. Yield isn’t a concern, only quality. I’d like to get the most out of the genetics potential as far as terps, cannabinoids, bud structure etc. but I don’t need a high yield.

I just setup my SE3000 in my 3x3x72” tent. Anyone have a PAR reading yet at 10”, 14”, 18” yet? I’m in week 3 of veg hanging at 18” and she seems to want a little more light but I don’t want to stress her out. My PAR meter is still a couple weeks from purchasing. Any helpful info would be appreciate. Thanks.

av8ersteve said:

I just setup my SE3000 in my 3x3x72” tent. Anyone have a PAR reading yet at 10”, 14”, 18” yet? I’m in week 3 of veg hanging at 18” and she seems to want a little more light but I don’t want to stress her out. My PAR meter is still a couple weeks from purchasing. Any helpful info would be appreciate. Thanks.

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At around 3 weeks of veg my SE3000 was set 27” at 45%…but my temps were lower 70s so maybe they couldnt handle much more.

Dothraki said:

At around 3 weeks of veg my SE3000 was set 27” at 45%…but my temps were lower 70s so maybe they couldnt handle much more.

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I've plugged in a heat lamp to warm my 4x4' flowering space while the were lights on when I need added heat...I like to have it at 78f - 80f in flower & veg . I started with a 150 watt dimmable light but I needed all 150 watts so making it dimmable was a waste of money but it worked and was cheaper to operate than my 1200w finned space heater. I then put a 50 w reptile lamp in my 3x3' tent and that worked great to bring it up to the temps I wanted........Night time only gets down to 65f at the coldest in my basement so I really only need the added heat through lights on...while running led only that is

Always with the se3000 stay at 18 to 24 from canopy, seeding i ran 45% 18 with a 18=6 light cycle im at week 10 85% punch gorilla autoflower and im looking amazing ps keep humidity up like 85% in seeding, Dom it tell it pops,humidity and temperature watch closely, never allow above 80 set for 75 to 77 and humidity at 85% tell flowering early flowering slowly turn down humidity, and don't over water, they are babies, and watch the stretch, the sf light chart is close,fans,humidity, size of tent temperature, soil, happy frog is very good, fox farm is widely available good stuff i use it