LED light intensity

wietefras

wietefras

Well-Known Member
Moflow said:
What is better, hanging a 200 watt led light at 18" and covering the canopy evenly with 1000 μmol/m2/s PPFD across it or lowering the wattage to 100 watts but lowering the now 100 watt led light until the ppfd rises to 1000 μmol/m2/s PPFD?
How will the yeild change and why.....?
Click to expand...
You will have better penetration when the light is closer. So more "depth" and therefore more useful yield lower down.

At least if the average PPFD is the same and not just in one spot.

I know even HPS gowers who actually drop their light closer to the plants in the final stages. They sacrifice the few buds that stick out on top to create a lot more extra yield lower down.
 
Moflow

Moflow

Well-Known Member
wietefras said:
You will have better penetration when the light is closer. So more "depth" and therefore more useful yield lower down.

At least if the average PPFD is the same and not just in one spot.

I know even HPS gowers who actually drop their light closer to the plants in the final stages. They sacrifice the few buds that stick out on top to create a lot more extra yield lower down.
Click to expand...
Will I get the same yeild for half the watts but the same ppfd though?

The HPS growers have no dimming capabilities, therefore their ppfd must go up as they put their lights closer to the plants for the same wattage.

But 100 watts of led v 200 watts of led using the grams per watt scenario at 1 gram per watt means 100 g/w for the 100 watt led light, that's Closer to the canopy, with the same PPFD as the 200 watt led that gets 200 g/w farther away with the same PPFD?

I think this needs more discussion to figure this out.
 
zypheruk

zypheruk

Well-Known Member
It will make for good debate ok, I'm a scrog grower so at most I would need is say 18inches of penetration which is all good, until you take into consideration how dense the canopy is. If all bud sites are two close together there ain't going to be to much light getting to the bottom 10 inches. Throwing more power is not really going to help. Training of the canopy in this instance is off more benefit than raw power. On my current grow I'm going to have to do two harvests, simply because my bud sites are two close together. So I will harvest the first 8 inches of buds first. Then the rest a week or two later. In an ideal world everyone would scrog their plants, saving power in a big way and getting better quality buds, less chance of bud rot etc. But it's not an ideal world. Some people like donkey dicks some prefer smaller quality mini dicks. We'll so the wife says.
We have efficient lights, now let's grow the plant in the most efficient way.
 
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giantsfan24

giantsfan24

Well-Known Member
zypheruk said:
It will make for good debate ok, I'm a scrog grower so at most I would need is say 18inches of penetration which is all good, until you take into consideration how dense the canopy is. If all bud sites are two close together there ain't going to be to much light getting to the bottom 10 inches. Throwing more power is not really going to help. Training of the canopy in this instance is off more benefit than raw power. On my current grow I'm going to have to do two harvests, simply because my bud sites are two close together. So I will harvest the first 8 inches of buds first. Then the rest a week or two later. In an ideal world everyone would scrog their plants, saving power in a big way and getting better quality buds, less chance of bud rot etc. But it's not an ideal world. Some people like donkey dicks some prefer smaller quality mini dicks. We'll so the wife says.
We have efficient lights, now let's grow the plant in the most efficient way.
Click to expand...
Great post!
 
Streetsports

Streetsports

Active Member
zypheruk said:
It will make for good debate ok, I'm a scrog grower so at most I would need is say 18inches of penetration which is all good, until you take into consideration how dense the canopy is. If all bud sites are two close together there ain't going to be to much light getting to the bottom 10 inches. Throwing more power is not really going to help. Training of the canopy in this instance is off more benefit than raw power. On my current grow I'm going to have to do two harvests, simply because my bud sites are two close together. So I will harvest the first 8 inches of buds first. Then the rest a week or two later. In an ideal world everyone would scrog their plants, saving power in a big way and getting better quality buds, less chance of bud rot etc. But it's not an ideal world. Some people like donkey dicks some prefer smaller quality mini dicks. We'll so the wife says.
We have efficient lights, now let's grow the plant in the most efficient way.
Click to expand...
I agree. It's highly situational.
zypheruk said:
It will make for good debate ok, I'm a scrog grower so at most I would need is say 18inches of penetration which is all good, until you take into consideration how dense the canopy is. If all bud sites are two close together there ain't going to be to much light getting to the bottom 10 inches. Throwing more power is not really going to help. Training of the canopy in this instance is off more benefit than raw power. On my current grow I'm going to have to do two harvests, simply because my bud sites are two close together. So I will harvest the first 8 inches of buds first. Then the rest a week or two later. In an ideal world everyone would scrog their plants, saving power in a big way and getting better quality buds, less chance of bud rot etc. But it's not an ideal world. Some people like donkey dicks some prefer smaller quality mini dicks. We'll so the wife says.
We have efficient lights, now let's grow the plant in the most efficient way.
Click to expand...
I agree. I scrog so that there's a small gap between the buds so it's better for me to run the light high enough to shine down between them. They're usually nice sized buds so I don't get good penetration when the light is too close because it would need to penetrate sideways through rows of bud.. I will get yellowing in the center and dark green around the perimeter though. The only ways to fix that are to raise it or dim it. As already stated by others, if I dim the light I will need to expect more grams per watt for the same yield. And have less light coverage.
 
zypheruk

zypheruk

Well-Known Member
Now imagine training and scrogging that same plant from the beginning rather than plopping a net on it and using it as a support net, I bet you could yield more with less power if you so wished.
Yes it takes effort and time by the grower, but that's free more so when a personal grow..
Nice plant and setup either way.
 
booms111

booms111

Well-Known Member
Coming from my HPS history only I don't completely understand some of the info about LED intensity. I don't see how lowering the wattage on LED then lowering light would be better then raising the light and upping the wattage except for the plants right under the lowered light. Example would be using one 1k hps vs four 250hps over same size room and lowering 250's down on plants and keeping the 1k up high over canopy. The 1k intensity would beat the four 250s easily I would think with bigger thicker top buds and more filled out lowers.

Now I just ordered two 324 boards and a 320h driver and a 80inch tall tent so i can keep the light up high and run them at max wattage, is this hps like thinking wrong?
 
ANC

ANC

Well-Known Member
Moflow said:
What is better, hanging a 200 watt led light at 18" and covering the canopy evenly with 1000 μmol/m2/s PPFD across it or lowering the wattage to 100 watts but lowering the now 100 watt led light until the ppfd rises to 1000 μmol/m2/s PPFD?
How will the yeild change and why.....?
Click to expand...


You already know the answer.

A shallow field of light will be most economical on a sea of many small plants.
 
tomate

tomate

Well-Known Member
Moflow said:
But 100 watts of led v 200 watts of led using the grams per watt scenario at 1 gram per watt means 100 g/w for the 100 watt led light, that's Closer to the canopy, with the same PPFD as the 200 watt led that gets 200 g/w farther away with the same PPFD?
Click to expand...
It depends, and there is no one right answer.
For each fixture at a given wattage there is an optimal distance to the canopy or better said a sweetspot of uniformity, penetration and avg. light density. So every single fixture (strips, QBs, COBs) has its own sweetspot that depends on how the light sources are arranged and how hard they are driven, and therefore there will be also an optimal wattage and a corresponding distance and this all depends on which avg. light density you are aiming for.
 
wietefras

wietefras

Well-Known Member
Moflow said:
Will I get the same yeild for half the watts but the same ppfd though?

But 100 watts of led v 200 watts of led using the grams per watt scenario at 1 gram per watt means 100 g/w for the 100 watt led light, that's Closer to the canopy, with the same PPFD as the 200 watt led that gets 200 g/w farther away with the same PPFD?
Click to expand...
Well that was the premise of the question. Half the watts same PPFD. It's a theoretical exercise, not a reality.

Like I said, if that's average PPFD then the plants get teh same amount of light in both cases, so ythe yield will be similar. Slightly higher on the side with lower light since it gives more penetration.
 
wietefras

wietefras

Well-Known Member
tomate said:
For each fixture at a given wattage there is an optimal distance to the canopy or better said a sweetspot of uniformity, penetration and avg. light density.
Click to expand...
The optimal height does not really depend on wattage though. Not with leds.

For a led fixture you create the correct uniformity by adjusting the height. You want the dark spots to get at least 80% of the average light intensity. That's a relative comparison. If you then crank up the watts and double it, the light distribution is still the same and therefore correct. The plants simply receive more light. If it's too much light then you should dim it back down. Not raise the light.

Some people hang their lights way to high. You can in fact lose half the light by doing that. In a 2'x2' tent you can easily lose half the light by hanging the fixture say 20" higher than optimal. Smaller tents are more hurt by wall reflection losses.
 
nfhiggs

nfhiggs

Well-Known Member
booms111 said:
Coming from my HPS history only I don't completely understand some of the info about LED intensity. I don't see how lowering the wattage on LED then lowering light would be better then raising the light and upping the wattage except for the plants right under the lowered light. Example would be using one 1k hps vs four 250hps over same size room and lowering 250's down on plants and keeping the 1k up high over canopy. The 1k intensity would beat the four 250s easily I would think with bigger thicker top buds and more filled out lowers.

Now I just ordered two 324 boards and a 320h driver and a 80inch tall tent so i can keep the light up high and run them at max wattage, is this hps like thinking wrong?
Click to expand...
I dispelled this myth recently:


This is what you get with a single 200W light source
one cob.jpg
The 1000 to 500 uMol zone is 12" deep.
Here is what four 50W light sources looks like:
four cob.jpg
You'll notice that while you still have 250 uMol at the floor, the 1000 to 500 uMol zone is higher and stretched out. the "zone" is closer to 18" in depth.

Lets see what eight looks like:
eight cob.jpg
As you can see - the floor is still at 250 uMols, and the "zone" is stretched to about 21".

In reality, penetration is not about having a high initial intensity single light source - its about how many PAR watts you're putting in and how uniform you can spread those photons.
 
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