legalcanada
Well-Known Member
but the further they travel the further they are spread out, equaling a lower concentration of light per sqf
LED light intensity
- Thread starter giantsfan24
- Start date
wietefras
Well-Known Member
That's semantically more correct yes. However the point is that this is only true for a very short range in a grow area with reflective walls. The light can't spread any further than the walls. It's then either absorbed or bounced back.
If we don't properly account for reflections (wall losses) and simply assume 100% of the light gets reflected off the walls (as was done in the mosaics) then this is what the distribution for one light source would look like:
No light is lost and therefore the average PPFD remains the same from top to bottom.I assumed 1000umol/s/m2
With a single light source (and 100% reflectivity), at 40% of the chart the light has been distributed enough to have the canopy there. From that point on down the light is (almost) fully uniform.
Of course in the real world we do have walls with imperfect reflections and part of the light that hits the wall gets absorbed. That's how we lose light when we increase the height and that's what the charts I posted earlier showed. "Wall losses" are related to the amount of wall that gets hit by the light. Which means this is a linear dropoff as height increases. Usually it's somewhere between 1% to 2% per inch, but it could be a lot more in a very small tent or much less in a very large room. Also with poor reflectance of the wall material it obviously will be more then with a highly reflective surface.
Either way, it doesn't matter at what height you start, you cut the average intensity by half after the same distance. There is no larger "depth" with fewer or more light sources. Not with 100% reflectivity and not with real world reflectivity either.
Of course the distribution of light will be slightly less uniform with fewer light sources, but it's still well within accepted tolerances because that's how we determine the height of the fixture above the canopy to begin with.
The only true issue related to number of light sources is the wall losses. A single light source needs much more height for the light distribution to be uniform than a fixture with multiple light sources. That's why hanging a single COB, board or strip in the middle of a 2'x2' space is generally a bad idea. You then need 18" height which can easily cost you 20 to 40% of the light. Using 4 light sources you can half that distance and thus cut the wall losses in half. Although this ends at some point since you cannot go too close either, because then you would need too many adjustments of the height over time and slight irregularities in plant height quickly become a nuisance.
Slinging PAR
Well-Known Member
I was making it as a general statement for all not just yourself. There is so much nit picking back and forth that almost all threads eventually devolve into a troll fest. Probably because people are bored now that LED has proven its place in replacing HPS.
I will say this, we don't know all of the relevant science yet. Research and studies are still going on that might introduce the next big leap.
wietefras
Well-Known Member
Keep dreaming.
Or maybe not. If anything, that's the problem. People expecting/wishing some magical "giant leap" suddenly coming up. That's why we get these bullshit "superior" light spectrum discussions or nonsense about "maximum DLI".
Or when people draw some silly chart or perform some experiment with a conclusion that goes against anything we hold true. Then they don't think "Hmmm maybe my chart/experiment is nonsense", but they go with "OMG I found something completely new!!!! We've been doing it all wrong. Magical bullet right here y'all! Step right up"
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Slinging PAR
Well-Known Member
Well I tried. You are just stupid. Fixing stupid is a pointless task.
Over the years on this forum you have proven time and time again that you have basically no clue. After that long you would think a person would learn something, but no, you have proven that to be wrong. Instead you mock others to compensate for your failure to understand and throw a hissy fit when those knowledgeable disagree with you. My grandchildren are better behaved.
His chart is right, your garbage is non-sense. Rather than point out why you are obviously wrong it is just easier to sit back and laugh. Makes no difference to me whether you learn or not, you have every right to remain blissfully ignorant.
Slinging PAR
Well-Known Member
Yeah but you also have plants and other objects in the space. For a comparison perspective it is fine though.
Par/PPFD map tells better story.
jarvild
Well-Known Member
Just what reference are they using for the left graph? And are they using a reflector on the HPS side? I doubt there is much use for that data as there is definitely no light hitting my ceilings or walls at 30 cm with a reflector in use.
a mongo frog
Well-Known Member
So who are you really? What banned account?
Slinging PAR
Well-Known Member
Does it matter?
a mongo frog
Well-Known Member
Are you referring to the Linkin Park song? Not sure what you mean?
Moflow
Well-Known Member
Surely the pic on the left, the colours are wrong?
The orange colour should be pointing down and not up, as the central ppf is stronger than the edges of the lamp.
Disregard the umols in the pics.
zypheruk
Well-Known Member
Fuck it I'm gonna say it and please no one don't take this personally this is a stupid fucking thread. No matter how smart any of us think we are, not one of us can give an exact answer. All these charts etc are a waste of time, they are based on an ideal space with no obstacles, eg do they have an 18inch canopy that is like a jungle, NO. Have any of them done a test with a defoliated canopy NO. I think the empty spaces are in our heads.
Grow some weed and be happy that you can actually grow.
RANT over, it's the weekend after all.
Grow some weed and be happy that you can actually grow.
RANT over, it's the weekend after all.
wietefras
Well-Known Member
Could very well be. The HPS will have a much wider beam angle than leds. So it makes sense that it spreads the light much better. While the led fixture seems to have a ridiculously tight beam angle.
They are not selling their fixture very well though. Going by the colors, the HPS has much better uniformity and light levels where it matters. The led fixture seems to project only a bright spot of light on the floor. This is a typical problem with those led boxes though. That's why our lights are vastly superior to the off-the-shelf led boxes. We spread out our COBs/strips much better and get much better uniformity much faster. So you don't need to hang the light 20" high in an effort to get some light to the edges of the grow, but 10" or even less is enough.
What is "misleading" is the PPFD measurements. Which clearly are only center line measurements. The colors clearly show they are trying to mislead us though.
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wietefras
Well-Known Member
Heh do I agree and that's even what I said in my first post already. You'd need to account for the LAI to begin to guess how much light falls through the canopy. Which is not something that will be the same for everyone or even between grows.
Still, I feel the basics of physics should be explained properly to people because otherwise people make the wrong decisions. Understanding these principles properly helps you to understand what the optimal height is for the fixtures we built. The optimal distance is determined by where you get a decent uniformity of light distribution. Also that you shouldn't increase height from that optimal distance to reduce the light intensity on the plants, but that you should use dimming (if possible).
So in the end you can benefit from correctly applying science instead of just saying "fuck it I don't know exactly, so who cares"
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wietefras
Well-Known Member
Maybe they are using one of those hoods which are open on two sides? Those will throw light out hose open ends, which would then get reflected onto the ceiling
zypheruk
Well-Known Member
Not many of us diy folks are using lenses, or have reflectors with a diode in the middle. That's why with store panels that are using reflectors etc you need them higher above the canopy than a diy fixture, if you don't they will fry or stunt the growth of the plant. But put the same light mods on diy and bang same thing, a tight beam of light depending on the angle of reflection. A HPS fixture only uses a hood which is not efficient and scatters light every where.
zypheruk
Well-Known Member
@wietefras looks like we where typing and posting at the same time lol sos. Well that's me the trichomes r doing their job and the beers doing it's thing. So in a nutshell I'm fucked later all. Have a good weekend.
Slinging PAR
Well-Known Member
Just ignore his blathering, he doesn't have a clue.