Some calculations about LIGHT

[Iammygod]

Spectrum and intensity both matter to our plants and us indirectly. Assume we cant change spec as each light technology has its own unchangeable spec(almost) But we can change the intensity by using more power lights. The lights with the same technology that consume more watt give us the same spec but more intensity in all levels.

We know plant's leaf need a range of intensiy meaning not too much and not low level of light; Too level of light reduce the Photosynthesis and plants cant handle too level of lights.

Lets assume leaf needs the intensity between X and Y. We can define N by this equation: Y=X/N². Remember, N is always exist. So we can say leaf needs the intensity between X and X/N².

Right near the light, intensity have to be very higher than X otherwise no leaf will receive right intensity. Based on invers Square Law of light somewhere we have X intensity. We let A be the distance to the light source where the intensity is X. As our assumption says the Photosynthesis with be stopped at intensity lower than X/N² If we apply ISL law again we get NA as distance form the light that photosynthesis stop working. Nebula has a definition in her website, Sweet spot and our calculations say that Sweet Spot should have A(N-1) height. N depends on plant type. A can be changed by useing different power lights. The more powerful lights have higher A parameter and inversly. If A goes higher in a light, A(N-1) goes higher meaning that light have bigger SS zone.

Our simple model can explain many stuffs including CFL weaknesses, Defoliation and many more.

If you need to place CFLs as close as possible it means CFLs have very low A parameter and so they have very low height SS zone. Thats why you cant grow tall plants useing CFLs.

The leaves have been placed A(N-1) form the light dont get enough light and we deflate them.

we exchanged U watt light with a M²U watt one. If A is the parameter of U watt light So the parameter of the M²U whatt light with the same technology should be MA(based on ISL)

If a light emitting technology with parameter A produce C² times more light than another technology, then the parameter of same wattage of the stronger technology should be AC, based on ISL.

HPS(150lumen/watt) are C²=2.5 times more efficient than CFL(60lumen/watt). we know A is about 2-4 inches for a 32 wahtt CFL so we can calculate that the parameter A of a 600 watt HPS is qurt(MC), where M²=600/32 and C²=2.5. Doing the calculations we get 7-27 inche for a 600 watt HPSs



We can even Estimate N. I use data ive learnt form Nebula. 35k-85k lux. We let X=85000 and Y=35000 and we get N=1.5. So you can defoliate such a way u have A/2 long colas(its just a simple model. Plants grow as they form their buds so you better defoliat leaves 2A away from the light to have A long height buds not A/2)

ALTOGETHER: the further the light should be installed, the better penetration the light has. SUN is the must power light we can see in our life. we need to place our plant 150 million kilometers away form the sun and because of this very high A parameter the sun have, she has really great SS zone, 1000s of kilometers.

Now tell me why well-designed 5watt LEDs with almost perfect spec that should be place higher than HPSs, can't defeat HPSs? LEDs produce Photons with almost the same reletive intensity as the chlorophyll can absorb. I REALLY NEED EXPLANATION, because i heard for many ppl i real trust their acknowledge and experiences that LEDs still can defeat HPSs watt-for-watt

[NebulaHaze]

I think it might help you to look at the actual results growers are getting instead of focusing so hard on the numbers, because that's what's going to matter to you most as a grower. It seems like from your last post that you have your conclusion already and you're trying to work back to prove it. Some things are currently unexplainable, and we might not have the scientific knowledge to explain exactly why something works the way it does, but we can still look at the results people are getting in real life to estimate what we can expect in our own grow room on a practical level.

That being said, I do have a few theories because I've actually wondered about this too. I think it may partly have to do with the fact that large bulbs are a single source of light like the sun, while LEDs are made up of many small sources of light. A single diode loses intensity faster than a larger source of light. So you can compensate with lenses, and with lenses you can direct the light down strongly, but the plant doesn't grow properly if the light from a single-color LED doesn't get dispersed enough with a wide angle lens to mix with the other colors. We've learned that plants need a mix of blue, red and a small bit of green to achieve the healthiest plant growth, and if they're only getting one color beaming down on them, often the plant doesn't grow as well as it could and leaves are more likely to experience deficiencies, whether it's radish or cannabis. So you can't focus purely on penetration when designing LEDs, you also have to worry about spread.

We've actually learned a lot about how light spectrum affects plants in the last couple of years. It's interesting, because it's actually NASA on the forefront of LED grow light experimentation on plants because they're trying to learn how to use them in space to grow fresh food. They've demonstrated how important the green spectrum is to plant growth, especially in bigger and more complex plants.

You might find this interesting from the Wikipedia entry about LEDs:

Though plants can grow under only red light, they often display unhealthy growth. It has been shown that many plants will grow normally if given both red and blue light.[20][21][22] However, many studies indicate that even with blue light added to red LEDs, plant growth is still better under light supplemented with green.[23][24][25]

In tests conducted by Philips Lighting on LED grow lights to find an optimal light recipe for growing various vegetables in greenhouses, they found that the following aspects of light affects both plant growth (photosynthesis) and plant development (morphology): light intensity, total light over time, light at which moment of the day, light/dark period per day, light quality (spectrum), light direction and light distribution over the plants. However it's noted that in tests between tomatoes, mini cucumbers and bell peppers, the optimal light recipe was not the same for all plants, and varied depending on both the crop and the region, so currently they must optimize LED lighting in greenhouses based on trial and error. They've shown that LED light affects disease resistance, taste and nutritional levels, but as of 2014 they haven't found a way to use that information practically yet.[26]

Here's another interesting fact about spectrum and plant growth that we're just learning about now. Not only can plants photosynthesize light from all parts of the spectrum, green light penetrates further down into the canopy than red and blue light, which get mostly absorbed by the upper leaves. This adds to amount of photosynthesis happening to leaves further down on the plant in addition to helping the plant grow more healthfully (check out some studies by NASA and others).

It's just not as simple as which light produces the highest level of photosynthesis when it comes to results. As another example, one LED could be really great at getting the plant to grow huge leaves, but if that doesn't result in increased buds than growers don't care. It's about figuring out what works with the unique chemistry of a cannabis plant to get it to make more and stronger buds. HPS lights do produce plenty of green (which isn't as efficient for photosynthesis as red or blue), but the total combination of light happens to produce a spectrum and intensity that gets really amazing results with flowering cannabis plants. I'm not saying LEDs can't get there if someone gets the spectrum and lenses right, but at least in general they haven't been quite able to match HPS lights yet.

The spectrum does affect on how the plant grows (check out photomorphogenesis) but in many cases not as much of an effect as the total amount of light energy being provided (photosynthesis) as long as the plant is healthy. But those are all just thoughts to try to explain what I've seen with my own eyes. In the end it seems like when all other things are equal, cannabis bud yields are often in direct proportion to how much light gets put out by the light, whether it's HPS, fluorescents, induction lighting, Metal Halides and LEDs. Ultimately, HPS lights simply put out the most light/watt of any grow light, at least with the current technology. It's definitely not a perfect estimate to determine yields, but it seems to give you a good ballpark figure.

To use CFLs as one last example about light spectrum vs light power (spectral irradiance), as I'm sure you know it's recommended to give plants 6500k (blue) CFLs in the vegetative stage, and 2700k (red) CFLs in the flowering stage, to promote vegetative and flowering growth. But they also sell 5000k bulbs, which contain a whole lot of green. From how we're often taught about light in the growing world, you'd think the 5000k CFL bulbs would achieve less yields than say 2700k in the flowering stage because plants "don't photosynthesize green as well." While that may be true to some extent, it's hard to spot in grow tests. The total amount of power seems to have a much larger effect than spectrum when it comes to how much the buds fatten up under CFLs. When I first started growing (I started with CFLs) I accidentally bought a huge photography bulb that was 5000k, but I still used it. When I grew it side by side against a 2700k bulb in the flowering stage, I couldn't tell the difference between the plants that were under one vs another. This is an easy thing to test if you don't want to invest in an LED panel, and it seems to sort of go along with the results you get with LEDs.

When someone says you're getting "more" photosynthesis out of a certain spectrum of light, those effects appear to be relatively small compared to the total amount of power (spectral irradiance) plants are getting, at least when it comes to bud yields. In fact, when it comes to plant growth it's close enough that scientists used to use a rough estimation known as PAR (Photosynthetically Active Radiation) to estimate how much energy a plant is producing for a certain amount of light. They looked at the amount of total irradiance in the 400-700nm range, and used that to estimate the level of photosynthesis, because even though total photosynthesis varies a bit at different colors, an estimate based purely on irradiance is easier to measure, and close enough a lot of the time.

Anyways, I'm definitely not a scientist, or anything close. I just have an interest in learning more about plants and especially cannabis plants! We love experimenting to figure out what works best on a practical level so we can help teach others, and it's interesting to try to figure out on a scientific level why us growers get the results we do

[Pankace]

Some old tech can't be beat. As a guitar player I hear a lot about new digital amps that a company will suggest is better than anything before it, but any guitar player with experience will tell you nothings better than an old school tube powered head.

not yet same thing I get it. But the comparison stands.

[Steveo h]

Tube amps rock.

[Smokey McPot]

Spectrum and intensity both matter to our plants and us indirectly. Assume we cant change spec as each light technology has its own unchangeable spec(almost) But we can change the intensity by using more power lights. The lights with the same technology that consume more watt give us the same spec but more intensity in all levels.

I think this postulate is inaccurate. Luminous spectra and intensity can vary substantially due to material/manufacturing differences (e.g. glass composition determines refractive index/loss tangent, gas composition in discharge lamps) and specification differences (e.g. HOMO/LUMO levels and hence wavelength is determined by the differing work functions i.e. dopant concentration of semiconductor substrate of an LED but the quantum efficiency can be completely independent) mean spectra differ between bulbs. Unsurprisingly, they also cost different amount too.

A lot of the following, I think, is a misunderstanding of the 'sweet spot' and how those numbers are reached. Irradiance (luminous radiance) on Earth is approximately 1 kW.m^-2. Because the sun is so far away, the rays arriving in any square metre are parallel to each other. If you measure the power at 5cm above the ground, it's the same as at 50cm above the ground, because the same rays pass through both surfaces of integration. The tables serve as a guide to keeping the artificially imposed irradiance roughly equal throughout the plant, as it would be in nature.

Lets assume leaf needs the intensity between X and Y. We can define N by this equation: Y=X/N². Remember, N is always exist. So we can say leaf needs the intensity between X and X/N²...
Right near the light, intensity have to be very higher than X otherwise no leaf will receive right intensity. Based on invers Square Law of light somewhere we have X intensity. We let A be ... intensity lower than X/N² If we apply ISL law again...
Our simple model can explain many stuffs including CFL weaknesses, Defoliation and many more.
If a light emitting technology with parameter A produce C² times more light than another technology, then the parameter of same wattage of the stronger technology should be AC, based on ISL.

HPS(150lumen/watt) are C²=2.5 times more efficient than CFL(60lumen/watt). we know A is about 2-4 inches for a 32 wahtt CFL so we can calculate that the parameter A of a 600 watt HPS is qurt(MC), where M²=600/32 and C²=2.5. Doing the calculations we get ... I use data ive learnt form Nebula. 35k-85k lux. We let X=85000 and Y=35000 and we get N=1.5. So you can defoliate such a way u have A/2 long colas(its just a simple model. Plants grow as they form their buds so you better defoliat leaves 2A away from the light to have A long height buds not A/2)

I think your are working with an oversimplification of the problem which misses some details. For a start, you're looking at only two of a 4/5D problem. Try drawing it out; an isometric perspective may help. Picking a coordinate system is tough, I would say use Cartesian and then your objective function is the L2-norm between your light sources and growth-tips (i.e. sqrt(dx^2+dy^2)). If you were to defoliate every fan leaf intercepted by the rays traced between end points your plant will die. That would be too much. You need to "measure" the radiant fluence at a point in 3D space in the absence of your plant, integrate over time and maximise this value. But the better the plant grows, the more light it occludes and the lower your value will be. But the whole thing is nonsense because the plant is now being oversimplified. It's not a homogeneous volume. Monte Carlo simulation is a feasible analytical technique; the early symmetric dicot structure of the vegetating plant is easy to model but things rapidly change during the flowering period. Plants are structured recursively. Think about it. There's a balance to be struck between defoliating fan leaves to expose flowers to direct light and reducing the plant's potential yield. Unfortunately the only way to know what the potential yield is, is to grow the exact same phenotype under differing conditions. Repeatedly. Even if your experiment isn't a full factorial (or not even partial factorial when you're interested in trying out 2 or 3 lights), the repetitions are the most important. You can't plan ahead if you don't know how your phenotype responds to different conditions and stressors. Knowing how much room you have to leave for 3-4wks of growing after the 12/12 switch could be the difference between a magnum harvest for your monster bong and a bunch of foxtailed, light-bleached flowers that are pre-dried to 3%RH at chop. Take three equally sized cuttings, root them and flower one under LEDs, one under HPS, and one under MH. How much stretch can you expect for that one phenotype? Hint: it's three different lengths/ratios any way you look at it.

• geometry of plants; cylindrical top, sparsity of lower branches -- 'popcorn'=body-centred spheres, cubic cell=internodal spacing, cannabis sativa longer cf. C. Indica vs. christmas tree (cones & fill factor)
• collimated light vs divergent sources, reflector geometry & purpose. flood vs throw. parabolics & barn. (thermal managmnt). reflection efficiency
• xy-plane fill factor of merit vs integral(iradiance(z)) & intersection of solid angle - subtended by leaf surface area - of hemispheres and cones
• trellis cylinder, w/ bare bulb/vertical light mover scenario?

Now let's talk biochemistry. Auxins, specifically, apical dominance, the xylem/phloem and transpiration's effect..
Actually I need to sleep. I'll try to come back to finish this tomorrow but there's a lot of ground to cover.
[ this space intentionally left un-blank? ]

• internodal spacing vs yield/linear length of stem
• container size, root pruning. light deprivation and corresponding reduction in leaf surface area (pic of WW1605-II??)
• uniformity is king; equal utilisation of all resource, max yield=max efficiency. consistency is predictable. dat control chart.

[s]While irradiance is a simple measure, yield mass is actually proportional to spectral fluence. But it's a ball-ache to measure accurately. You have extrapolations far beyond their prediction power.[/s]

[Iammygod]

but the plant doesn't grow properly if the light from a single-color LED doesn't get dispersed enough with a wide angle lens to mix with the other colors. We've learned that plants need a mix of blue, red and a small bit of green to achieve the healthiest plant growth, and if they're only getting one color beaming down on them, often the plant doesn't grow as well as it could and leaves are more likely to experience deficiencies, whether it's radish or cannabis. So you can't focus purely on penetration when designing LEDs, you also have to worry about spread.

Good point. I've thought about it before. Ive read many LED panels specifications, many of them are like candle even they use much much power. But there are some LEDs panels that are able to act better than HPSs and even Sun.

Many 3watt LED planel use 90 degree lenses and should be placed at 18" height. A well-designed LED panel use 5 watt LEDs and should be placed at 24" height for the same intensity at the top of the plants. Im going to say 5watt LEDs disperse light much better than 3 watt because they have bigger footprint.

large bulbs are a single source of light like the sun, while LEDs are made up of many small sources of light. A single diode loses intensity faster than a larger source of light

I think both above and below text can be true at the same time meaning only one of them can be true



Let me say how i think.

Sun moves in the sky but our light dont. This sun movement let many leaves to receive light. We place our light right at the top of the plants. In this situation top leaves always block light. Although our artificial lights dont move but a reflector can help plants receive more light in compare of LEDs.
We know HPSs use reflector and LEDs use lenses. Both lenses and reflector have its own pros and cons. A Reflector can allow light to reach to lower leaves because light reflected by the side of the reflector wall is a way to lower leaves. Lenses can help intensity but it make more parallel light. Sun's light is also parallel but sun moves and LEDs dont move. That why i belive LEDs need light moving system more than HPSs.

Altogether im thinking well-designed 5watt LEDs(not 3watt) can get better results than HPSs.

You are theoretically right that two x watt LEDs are better that a 2x watt LED panel. But i think we get better results with a 2x watt LED and a light mover in compare of two x watt LED

Movement is what LEDs need more than HPSs

Guide me. Tell me your idea please

In the http://www.growweedeasy.com/led-grow-lights you mentioned that "Generally your goal with LED panels should be 50-60 watts per square foot of grow space to get the best results.". In this article we read P600 covers even 3×5. But in this footprint every squar feet only gets 24 watt. You think 24 watt LED per squar feet can reach good results? If so why LEDs still are not better that HPS that needs at least 37 watt per squar feet?

[SiriusFourside]

The first two sentences you quoted aren't mutually exclusive.

• "large bulbs are a single source of light like the sun, while LEDs are made up of many small sources of light. A single diode loses intensity faster than a larger source of light"
  • A large source of light loses intensity over distance slower than a small light - True
• "With LED grow lights, you will generally get better results with more smaller LED panels than a few big LED panels. For example, you will often get better results with 2 x 125W LEDs (total 250W) than you would with a single LED model that produces 250W. This is because more panels often make it easier for you to spread the light to where it's needed."
  • Using a small array of panels ends up being more efficient than a single large panel of equal wattage - True

You've already gotten a few well thought out and accurate responses from Nebula (if you include the other thread) as well some math/science wizardry in the post before yours. You say stuff like "guide me", but it seems like what you really want is for someone to tell you to get an LED.

I'm not being facetious here: you really should get an LED. I'd bet you'll be super happy with one!

[Iammygod]

The first two sentences you quoted aren't mutually exclusive.

• "large bulbs are a single source of light like the sun, while LEDs are made up of many small sources of light. A single diode loses intensity faster than a larger source of light"
  • A large source of light loses intensity over distance slower than a small light - True
• "With LED grow lights, you will generally get better results with more smaller LED panels than a few big LED panels. For example, you will often get better results with 2 x 125W LEDs (total 250W) than you would with a single LED model that produces 250W. This is because more panels often make it easier for you to spread the light to where it's needed."
  • Using a small array of panels ends up being more efficient than a single large panel of equal wattage - True

You say stuff like "guide me", but it seems like what you really want is for someone to tell you to get an LED.

Not at all. Im just trying to understand thoeries. If Nebula Says HPS is better, for me it means HPS is better for sure. These questions im asking dosent mean she is wrong at all. I trust her completely. Im telling my idea and asking her to correct me. Thats all.

[Iammygod]

[*]A large source of light loses intensity over distance slower than a small light - True[*]Using a small array of panels ends up being more efficient than a single large panel of equal wattage - True

These 2 are a little Contradictory to me.

Small source of light losses intensity over distance faster than big light but a array of panel that use many but smaller watt ends up more efficient although they lose intensity faster?

I think LEDs have a big problem that can be solved easily using a light mover. Because of lenses they use, They make almost parallel photons and that's why 2 smaller LED end up better results than a big LED panel with the same watt. Lower leaves of a plant under 2 LEDs can receive light. I think 5 watt LEDs have better penetration than HPS but the light they emit dosent have an effective way to reach lower leaves.

[Iammygod]

Am i wrong with this thought:

"LEDs need a light mover, otherwise they get smaller germ/watt in compare of HPSs because they are not able to support lower leaves efficiently. LEDs emit almost parallel photons and need straight way to reach lower leaves but HPS emit photons in 360 degree and these photon can reach lower leaves by reflecting from the walls."

[NebulaHaze]

LEDs need a light mover

I've also wondered about light movers with LEDs. If you have a garden with many LEDs, often it seems like the parts of the plant located in between the panels are the healthiest. To me this indicates that the mixing of the spectrum (or possibly the angle/intensity that the light is getting to them) has a positive effect on the plants. However when we got a light mover to try with an LED to test this hypothesis, we realized it didn't work well on a practical level. The light movers available are not that tough, and have a hard time handling the increased weight of an LED panel (LED panels can weigh quite a bit more than HPS lights of similar wattage). You need to be careful when hoisting lights up to make sure not to pull on the apparatus or it will break. They also don't fit well in a grow tent (and take almost a foot of height by themselves), so it seems like they're much better suited to a room with plenty of height than a tent. We ended up tossing our light mover because it just doesn't work for 4'x4'x7' tent with a big LED, but I know I'd be interested in the results someone got from an LED in a room with a light mover.

[Iammygod]

I've also wondered about light movers with LEDs. If you have a garden with many LEDs, often it seems like the parts of the plant located in between the panels are the healthiest. To me this indicates that the mixing of the spectrum (or possibly the angle/intensity that the light is getting to them) has a positive effect on the plants. However when we got a light mover to try with an LED to test this hypothesis, we realized it didn't work well on a practical level. The light movers available are not that tough, and have a hard time handling the increased weight of an LED panel (LED panels can weigh quite a bit more than HPS lights of similar wattage). You need to be careful when hoisting lights up to make sure not to pull on the apparatus or it will break. They also don't fit well in a grow tent (and take almost a foot of height by themselves), so it seems like they're much better suited to a room with plenty of height than a tent. We ended up tossing our light mover because it just doesn't work for 4'x4'x7' tent with a big LED, but I know I'd be interested in the results someone got from an LED in a room with a light mover.

Finally we found something in common. You know ive never grown real plants in my life but im planing to. Although ive never grown in reality but ive harvested many plants in my mind.

As i mentioned in previous posts, after a liitle discussion i had with SiriusFourside, lower part of a plant cant get much light from its top LED. Maybe thats one of the reasons we get better results with 2 or more separate planel (or HPS in small setup) although the bigger panels have better intensity and penetration. But in larger setup with more panels this top leaves blocking effect will be disappeared.

When i was thinking about LED with lenses after i read your article about LEDs(and wikipedia to understand how LEDs work) i asked myself how light emitted by an LED can reach the lower part of a plant right under that LED. Top leaves always block the only way to the lower part. I thought light movers can solve this prob a little. I knew HPS can have this problem much less because they reflect light such a way that there are many ways to lower part of the plant right under its reflector. but i knew in the big setup im planning containing (4) 1000 watt LED to cover 9×9 feet, it's not going to be a big problem.

[Royal Nugs]

Lol... you guys lost me a long time ago.

I had to share this though: I just can't stop picturing lammygod as some stereotypical mad scientist with photocells and LED chips strewn about his laboratory with a whiteboard in the back with some rediculous equations (see above) on it. He's got to have a cool accent too.

I can hear him cackling now...

[insomniaczzz]

Lol... you guys lost me a long time ago.

I had to share this though: I just can't stop picturing lammygod as some stereotypical mad scientist with photocells and LED chips strewn about his laboratory with a whiteboard in the back with some rediculous equations (see above) on it. He's got to have a cool accent too.

I can hear him cackling now...

I'm picturing either Johnny Lee Miller (Sherlock) or Yannick Bisson (Murdoch). teehee

[Smokey McPot]

You know ive never grown real plants in my life but im planing to. Although ive never grown in reality but ive harvested many plants in my mind.

You should really read GWE #232 Learning Hard Lessons the Easy Way.

separate planel (or HPS in small setup) although the bigger panels have better intensity and penetration. But in larger setup with more panels this top leaves blocking effect will be disappeared.

When i was thinking about LED with lenses after i read your article about LEDs(and wikipedia to understand how LEDs work) i asked myself how light emitted by an LED can reach the lower part of a plant right under that LED. Top leaves always block the only way to the lower part. I thought light movers can solve this prob a little. I knew HPS can have this problem much less because they reflect light such a way that there are many ways to lower part of the plant right under its reflector. but i knew in the big setup im planning containing (4) 1000 watt LED to cover 9×9 feet, it's not going to be a big problem.

Yeah, this is pretty much the crux of the problem.
Go sprout some seeds and grow a plant. Don't get 4+kW without every growing a plant or four. Learn the basics under 600W or something. You can't force a plant to grow, it's going to do its own thing. You need to be flexible in guiding it and catering to its needs. The poor girls just want to reproduce.

[Royal Nugs]

LOL! Many Bud, such cola. DOGE FTW!

[NebulaHaze]

I have some dogecoins somewhere, not sure how I got mixed up in all that haha