Streetsports
Active Member
I thought green is only useful when being used in bright white light.
LED light intensity
- Thread starter giantsfan24
- Start date
Streetsports
Active Member
"The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques."
Slinging PAR
Well-Known Member
Lots of research out there!
Great textbook detail !
giantsfan24
Well-Known Member
If my light has at max power puts out, say, 967 μmol/m2/s PPFD at 18" would it be half that for 50% power? I've got a 200w light, I run it at 100w. Would that reduce the output by 50%?
Viceman666
Well-Known Member
No because youll be gaining in efficiency but really it depends on your build.. if you use the same driver then youll be loosing efficiency by not running close to max power but gain on the light itself.. but not its not you cut power in half and get half the power output its more complicated than that hehe
giantsfan24
Well-Known Member
That's what I thought too, thanks for the confirmation...I can't think of the term for it though...
Thanks!
Moflow
Well-Known Member
And also, what happens if you lower light to 9" and reduce power until you get 967 PPFD again?
giantsfan24
Well-Known Member
967 is my max so...sorry not sure I understand your question. (which should surprise no one lol)
I just got off the phone with @RainDan and he cleared a lot of my questions up. Very knowledgeable guy and I'm glad I bought my light from them. I think what I'm dealing with more than anything else is a couple of bad seeds. One that's mutated and another that isn't what the seed dealer said it was whether or not they knew is another story but I'm just going with inferior seed batch.
OneHitDone
Well-Known Member
You get a very shallow depth of high intensity light. "Lack of penetration"
giantsfan24
Well-Known Member
That's interesting and would be the opposite of what one may think..
Streetsports
Active Member
You may be thinking of intensity. I think overall penetration has to do with line of sight to the light source, which is better as you raise the light. But intensity goes down. It's probably the opposite when using something like a quantum board setup or strips though. (Lower intensity but a larger spread of diodes). Obviously if you raise the light too high then the intensity becomes too low. I wonder if this is why more people seem to raise the light rather than dim the light.
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OneHitDone
Well-Known Member
I could be way off on this but I doubt it.
Its kinda like this - lot's of small low power diodes give you this
Single High power source such as 1000W HPS or those Jumbo cobs give you this
Its kinda like this - lot's of small low power diodes give you this
Single High power source such as 1000W HPS or those Jumbo cobs give you this
giantsfan24
Well-Known Member
He mentioned light intensity in the post so...I would think the closer the light is to the plants the more intensity and penetration you'd get but I can' see where the penetration part would be better further away when I think about it.
Streetsports
Active Member
Because the light can shine down between the kolas better. The closer you get the light the more everything off center is shaded by other buds. This doesn't count when using an array of diodes though. Because each bud gets a better line of sight to a light source (less shadowing which means less dark spots.) That's why qb's and strips are getting so popular. I could be wrong. This is the internet lol. If so, someone will tell me so shortly. Shadows disapear as the sun moves over head.
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nachooo
Well-Known Member
I think strips and quantums may work like a mix between difusse and direct light which should make intracanopy lighting better and thermal leaf management easier for the plant and course better uniform lighting so at the end you can use even more PPFD with less light stress...etc...
wietefras
Well-Known Member
Penetration gets better when you get closer to the plants through line of sight too.
If you have plants with a close canopy. Look down at the canopy from far up. It will look like a closed green surface. When you get closer and closer and you start seeing more and more between the leaves.
So when hanging the lights closer to the plants you have more light (less of it lost on the walls) and more sight lines for the light between the leaves.
Streetsports
Active Member
I know you get better leaf penetration in the very center by lowering the light but i get light farther down into the whole plant by raising the light (overall penetration). To a certain point. Because light can penetrate thin leaves but not thick buds. Depends on the light source though. I can see the change in how much light makes it to the floor also. Lower the light and you get a bright spot in the center of the floor. Raise it and you get scatterered light all over the floor. I guess I'm talking about overall plant coverage and penetration (how many buds are getting direct light) and others are going by the deepest penetration point in the very center of the canopy.you may get a higher peak depth by lowering it but I feel at a certain point you're losing overall average depth. Depending on light source. Also depending on how big of buds you can grow. The buds in my avatar are in a 5x5. Some are as thick as a beer can. Light can't penetrate sideways through a few rows of those buds but it can easily shine down between them. If you look really closely at the bottom of the pic you'll see a gap to the floor. The floor is lit up. And the whole canopy is covered nicely. When I lowered the light, the outermost edges of the canopy and the outermost edges of the tent floor would darken. So, much less overall penetration of the plants but better in the very center. (The hot spot became smaller which made the best penetration area smaller. Higher peak but lower average.) I guess some of it is situational. Depends on the plants, growing technique, light and what you grow in. With or without walls etc.
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Moflow
Well-Known Member
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.....?
How will the yeild change and why.....?
wietefras
Well-Known Member
That's only temporary. When the lights are high you get more directional light and the leaves will aim for the light and close up ranks.