How far to keep your LED's / Quantum Boards from the canopy?

Kaotic

Well-Known Member
And I was gonna say if you see any white skinny stalk from seed and it’s lanky their reaching for the light
 

Blossom21

Active Member
And if you see any white skinny

yes you can keep lights lower for flowering it’s better for them, but just be sure to not to have them too close, I’ve had that problem once and my gelato plant gave me like 3.5 oz instead of a whopping 5 to 6.
Yeah i'm trying to figure out the optimized distance/power with my setup, just looking for more information/experience with this topic. So far haven't really got answers what i should do because it's not that long before harvest.
 

Blossom21

Active Member
Damn variables:-P...... No one can teach you how to read your plants on the internet, experience will though.
I recently read a comment that there would be cheap (maybe they were they called lux) meters that you could use to measure the light levels, and then use that as a reference to some numbers what would be too little or too much. I think the "maximum" usable amount was somewhere around 100k lux until you hit diminishing returns or something like that. I think it was somewhere in this forum where i read the comment, but can't remember where. I don't remember the details so i might be off a little, but i'm curious about that.

Of course i know there's zillion other variables too, but i'm hunting some kind of baseline to my light usage and try to optimize my setup with all other elements in mind too, i'm constantly learning more and more and wanna gain all knowledge i can from experienced growers too. If that explanation makes any sense to you :confused:

I wouldn't just wanna go growing without asking any advice and then repeat all the million mistakes others have already made before, if i can learn faster with good advice. I've learned most things about growing through internet and asking about them from different places, then making my own adjustments to get better results! I know there's different ways to measure light too, and different terms like PAR and LUX, so maybe i can get a deeper learning about them too.

I'm not expecting any perfect answer to MY own setup, just knowledge how i can learn the fastest to do it myself. Were it with some meter or taking some general advice and adjusting that little by little. All help is welcome of course, but i'm sure how cannabis reacts to light has been studied already pretty well, so for example someone could maybe hit me up with some good links or videos that i could/should watch, i would appreciate. :hump:
 
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GrassBurner

Well-Known Member
Everything im fixing to say comes from someone with less than 6 months of growing experience under my belt. I will tell you what I've seen so far.
In my 2'x3'x4' veg cabinet I run a single qb288 b spec. My first 2 grows, I ran Sour Bubba and Dracarys. They took all the light I could give them, about 12" above canopy. My 3rd run of AK Bean Brains NL1 and PHK, I had to mount the light about 2" from the ceiling (24" from canopy) and turn it down before they were happy.
In my 2'x4'x6' cabinet I run 4 qb120's on a 320 watt driver. I was running the light between around 18" above the canopy, but i recently added a Solacure UV light, which needs at least 24" from the canopy. So thats where I run the 120's, at probably 90% power.
 

Canada_420

Active Member
Sf4000 is a lot different than 288bds

You are correct, but he is looking for real life practice which I'm giving him
Hey man, currently running 2 sf2000s side by side. I keep mine at like 30 inches both running 75-80% power. Any more power I end up with burnt leaves. I also tried it close at 12" at about 45% but growth seemed better at 30" and 80%. Every environment and strain would make that difference imo. My sativas can take quite a bit more light than my indicas before they show the signs of burn.
 

MoroccanRoll

Well-Known Member
The factors you're trying to balance are illiuminance, heat and uniformity at the top of the canopy. First pic is measurement at the top of my canopy. Second pic is the the sun at 2:00 pm on October 6, 2020 at ~41 degrees north latitude. You can shoot for an illuminance somewhere in this range.

Screenshot_20201006-140017.cleaned.pngScreenshot_20201006-142032.cleaned.png

The next thing you have to do is make sure the top of the canopy doesn't get too hot. Excess heat leads to heat stress. If the temperature at the top of the canopy is uncomfortable for your hand, it's likely uncomfortable for your plants.

The third factor you have to consider is uniformity. I could get higher illuminance at the top of the canopy without excess heat but I prefer to increase the distance a little to get better uniformity across the canopy. Consider a single COB LED. This is pretty close to a point source. You could pull it down to within an inch of the top of the canopy and have hella illuminance directly below the LED but nothing at the edges of the canopy.

If you're curious about lux vs PAR, check this link. The conversions are approximate but probably close enough for our purposes. https://www.waveformlighting.com/horticulture/convert-lux-to-ppfd-online-calculator
 

Kaotic

Well-Known Member
What height would you recommend running a SF4000 with dimmer at for seedlings?
For seedlings I ran it at full light intensity at 30 inches now I’m at 28 I can go a bit lower but I’m at full intensity I want the most light for my plant and I don’t wanna burn her she will do just fine, she’s also keeping short no stretching at all , lights being so close is not needed.
 

Kaotic

Well-Known Member
Yeah i'm trying to figure out the optimized distance/power with my setup, just looking for more information/experience with this topic. So far haven't really got answers what i should do because it's not that long before harvest.
Honestly just put the flowers in optimal range from the light too far and too close is not bad and your plant will tell you if it needs more.
 

Kaotic

Well-Known Member
I recently read a comment that there would be cheap (maybe they were they called lux) meters that you could use to measure the light levels, and then use that as a reference to some numbers what would be too little or too much. I think the "maximum" usable amount was somewhere around 100k lux until you hit diminishing returns or something like that. I think it was somewhere in this forum where i read the comment, but can't remember where. I don't remember the details so i might be off a little, but i'm curious about that.

Of course i know there's zillion other variables too, but i'm hunting some kind of baseline to my light usage and try to optimize my setup with all other elements in mind too, i'm constantly learning more and more and wanna gain all knowledge i can from experienced growers too. If that explanation makes any sense to you :confused:

I wouldn't just wanna go growing without asking any advice and then repeat all the million mistakes others have already made before, if i can learn faster with good advice. I've learned most things about growing through internet and asking about them from different places, then making my own adjustments to get better results! I know there's different ways to measure light too, and different terms like PAR and LUX, so maybe i can get a deeper learning about them too.

I'm not expecting any perfect answer to MY own setup, just knowledge how i can learn the fastest to do it myself. Were it with some meter or taking some general advice and adjusting that little by little. All help is welcome of course, but i'm sure how cannabis reacts to light has been studied already pretty well, so for example someone could maybe hit me up with some good links or videos that i could/should watch, i would appreciate. :hump:
An optimum range with leds I would say no lower than 18 inches for strong QB’s
 

Smokinnewb

New Member
For seedlings I ran it at full light intensity at 30 inches now I’m at 28 I can go a bit lower but I’m at full intensity I want the most light for my plant and I don’t wanna burn her she will do just fine, she’s also keeping short no stretching at all , lights being so close is not needed.
Thank you
 

Blossom21

Active Member
Honestly just put the flowers in optimal range from the light too far and too close is not bad and your plant will tell you if it needs more.
How do i tell at day 40F if my plant needs more light? The major flower stretching is done already at this point too if i know anything, but sure they'll keep still growing at low pace.
 

Kaotic

Well-Known Member
How do i tell at day 40F if my plant needs more light? The major flower stretching is done already at this point too if i know anything, but sure they'll keep still growing at low pace.
If the leaves next to the flowers the sugar leaves I’m talking about, if they are standing straight up abnormally it might be too close to the light, if the leaves are slightly perked up it’s great and anymore higher your leafs may get burnt.
 

Kaotic

Well-Known Member
How do i tell at day 40F if my plant needs more light? The major flower stretching is done already at this point too if i know anything, but sure they'll keep still growing at low pace.
Also leaves getting crispy and yellow on top which forms is another sign of the lights being to close, but to me the leaf reacting to the light says it all
 

Kaotic

Well-Known Member
How do i tell at day 40F if my plant needs more light? The major flower stretching is done already at this point too if i know anything, but sure they'll keep still growing at low pace.
Here’s a great example , see how the leaves are 30 inches away and their perked slightly up that’s optimum, you can go a little lower but gradually go lower from there, to me the first signs of too much light and heat is the leaves start getting crispy and feel crispy then start to yellow next.
 

Blossom21

Active Member
If the leaves next to the flowers the sugar leaves I’m talking about, if they are standing straight up abnormally it might be too close to the light, if the leaves are slightly perked up it’s great and anymore higher your leafs may get burnt.
So far the leaves have been just staying leveled straight, but it's middle of the night so i'll do closer inspections tomorrow and tune up my tent at the same time.
Here’s a great example , see how the leaves are 30 inches away and their perked slightly up that’s optimum, you can go a little lower but gradually go lower from there, to me the first signs of too much light and heat is the leaves start getting crispy and feel crispy then start to yellow next.
Did you mean to post a picture? I don't see anything.
 

Kaotic

Well-Known Member
So far the leaves have been just staying leveled straight, but it's middle of the night so i'll do closer inspections tomorrow and tune up my tent at the same time.

Did you mean to post a picture? I don't see anything.
If the leaves are levels on top of plant and lights are on , then you can bring the lights down a few inches I say
 
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