The perfect LED spectrum

[PurpleGunRack]

• What's your guys take on the perfect spectrum for veg, transition and flowering respectively ?

• Where did you get your information or what experience did you have that made you see the light ?

• Please assume we're already pounding the plants with 1000 PPFD and just looking for the perfect spectrum both within PAR and the signalling wavelengths beyond PAR, and thus be able to find the recipe for the best combination of different CCT white light LEDs and supplemental mono diodes

Based on personal experience very little blue is needed to avoid non-genetical over stretch, according to NASA's studies 15 PPFD blue is sufficient for this, but some side by side grows, growers subjective experiences and the amount of blue found in a MH bulb suggests that a higher dose of blue than found in ie. 3000K could benefit the plants in the vegging state.
I have to say that 3000K is very good for vegging if the PPFD is decent, probably why it's the go to CCT and why it's always the first to sell out when a new batch of PCBs or strips hit the stores.

Transition or pre-flower is a bit more tricky, but with strips or COBs it's pretty easy to run somewhere between 50/50 and 70/30 3000K and 5000K each on its own dimmable driver, the question is just what ratio we need, and could we get the same result by just adding 10-20 blue mono diodes per m2 ?
Definitely add the Far Red here from 1 hour before lights out to 15 minutes after lights out but that's pretty much all I can say for sure, we know that works to quickly transition the plants to their respiration state.

So far I ''narrowed'' it down to 3000K 80CRI or something with more red for flowering.
Based on experience and observation aka hardly close to being scientific, but perhaps nod in the right direction.
Keeping the Far Red going here is most likely worthwhile based on the nature of short day plants.

There's not a lot of useful studies out there, and most are done on other species and often only on leaves in vacuum chambers or seedlings.
And most of the time tests on ligth is done by setting one narrow spectrum against another, like the Emerson experiments with 660nm, 730nm and both combined.
NASA's test are also done like this with a 1990's CFL as control and only 350 PPFD, and let's face it they're not doing their research to make it easier to grow cannabis in our houses, but to make it easier and more cost efficient to grow food in space
We kinda already figured that growing with 660nm (Photo Red) alone isn't the way to go, most of us know what sunlight looks like...


A few charts:

fluence-PAR-600.jpg

• PurpleGunRack
• Mar 27, 2018

Plant Absorption Peaks PAR & McCree curves Vs Sunlight.png

• PurpleGunRack
• Mar 27, 2018

So chime in with what you know, I don't think we can expect any universities or other non-commercial organizations to do some testing we can use directly in practical application any time soon.

​

 

[Mayne]

4100k is the best all around spectrum,

 

[TurboBucket]

I've been struggling to find a solution to this as well. One realization I have come to make is that there will never be "one best spectrum". I believe each Gardener is going to need a spectrum and environment balanced to individual strains to truly achieve their "optimal growth" each growers end goal is not guaranteed to be the same that alone changes the required input.

For example three growers with White widow, one striving for flower mass, one for flower thc% the other for oil volume. They would all have their own "best" recipe for their desired results.

Photomorphogenesis and manipulating plant growth with spectrum for each growers space now adds in a whole bunch of other variables. Imagine increasing the node spacing on your favorite typically super tight indica. Or being able to squash some of those big lanky sativas you can never keep out of the lights.

Don't forget the UVB.

So what's a grower to do? How do we build a lighting system to take into account the different variables we may encounter.

 

[Mayne]

/

 

[PurpleGunRack]

4100k is the best all around spectrum,

For what part of the cycle and based on what?

Why exactly 4100K?

I've been struggling to find a solution to this as well. One realization I have come to make is that there will never be "one best spectrum". I believe each Gardener is going to need a spectrum and environment balanced to individual strains to truly achieve their "optimal growth" each growers end goal is not guaranteed to be the same that alone changes the required input.

For example three growers with White widow, one striving for flower mass, one for flower thc% the other for oil volume. They would all have their own "best" recipe for their desired results.

Photomorphogenesis and manipulating plant growth with spectrum for each growers space now adds in a whole bunch of other variables. Imagine increasing the node spacing on your favorite typically super tight indica. Or being able to squash some of those big lanky sativas you can never keep out of the lights.

Don't forget the UVB.

So what's a grower to do? How do we build a lighting system to take into account the different variables we may encounter.

We have to consider the strain and light it appropriately, but it's mostly an issue when we grow landrace sativas and indicas, and though useful and interesting we need to establish some basic knowledge first like 3000K, 4000K and 5000K veg and flower comparisons.

Stretching an indica is easy enough, but tightning a sativa is probably only possible to a certain degree and the genes will dominate, but if it means you can manage it indoors it's a plus, the problem is how do we apply our lights to do it?

UVB might be worthwhile and it might not be and it's very unhealthy for living things, however UVA is pretty safe and easy to apply with mono diodes, but again I need a reason to and an understand of how, when and why before I want to spend money in that direction (or any... : ) )

Building the light is no problem, knowing what to put in it and how to use it right is the problem


:48;

 

[TurboBucket]

That's kinda my point. There is no "best" chip set. Personally I've opted for 4000k range as a base. I'll add the supplemental blues reds far red and uvb as the budget allows. With a chassis capable of running any color I want at any intensity I want I would be able to adjust with the plants through their growth cycle.

Most of my understanding behind color spectrum has admittedly come from manufactures and cross referenced where possible to agricultural crop studies.
Hydrofarm actually setup a big greenhouse and made a handful of videos about it using a guy named "Farmer Tyler" as the mouthpiece. You have to deal with some product plugs but there is a very good basis of knowledge available there.
You may already have a handle on all of that and actually be seeking the light recipes that folks either don't know or won't share.

 

[Mayne]

GreenGene and Growmau5 came to the conclusion, 4100K was the best all-a-round spectrum.. I really wish i could dig them up on the tube, but i think they are gone. utube stripped everything almost, at least the best ones..

alot of my knowing came from them 2.

 

[TurboBucket]

GreenGene and Growmau5 came to the conclusion, 4100K was the best all-a-round spectrum.. I really wish i could dig them up on the tube, but i think they are gone. utube stripped everything almost, at least the best ones..

alot of my knowing came from them 2.

You have now repeated yourself 3 times. Lol

If you want to buy one set of diodes yes. I suggest the 4000k range. They are not the BEST spectrum though. I'm done here. There will never be one perfect light for every situation. The sooner you can understand that the sooner you can build a tunable light. G'luck keep em green.

 

[Mayne]

You have now repeated yourself 3 times. Lol

If you want to buy one set of diodes yes. I suggest the 4000k range. They are not the BEST spectrum though. I'm done here. There will never be one perfect light for every situation. The sooner you can understand that the sooner you can build a tunable light. G'luck keep em green.

not sure what you mean. I only said it once, then asked why. *shruggs, not sure the problem.

I personally take word a very small crew that have done personal research on this subject. 4100k from start to finish if you had to pick one single Kelvin to grow from start to finish.

My rig is tunable. I use 3500K90CRI and 4000K80CRI, dimmable, with 730nm addition. What we need in this thread, is what do blues do, what do reds do,

and its not about mixing and this and that, its about the best spectrum to MAXIMIZE Photosynthesis rate. Which boils down to VPD, USUABLE Light, and nutes.

Each Spectrum does play different parts into the whole realm of things, I totally agree with that. Kinda funny, but these plants are like fat people trying to diet. Different things work for everyone, and not everyone can use the same plan, because its not universal. And the same can be said for these plants to an extent.

But if you get the basics down, you see pretty good results, using universal variables. Dont over water, dont over feed, and dont burn your plants with light heat.

 

[Mayne]

at the end of the day bro, we cant meter spectrum by the eyeballs, and need a true spectrometer to get proper data to come to a conclusion.

love to have one, lol..

 

[bluter]

best i've found is a mix of 3500 and 3000k. we use it as full spectrum running both thru veg and flower. eveything 90 CRI. components are super dependant on brand.

have built veg only as 4000k / 4500k and flower only as 3000 / 2700k, those were dedicated veg / flower. essentially identical results, but the lack of difference may be due to growing style and other factors.

money-wise i'd say 3000k / 3500k is a good buy if you have good brands and stick to 90 CRI. higher binned leds perform better period imo. a lot of what you are buying is the binning.

have built them with supplemental 5050 smd's to add a little dedicated far red. honestly can't say the 5050's do much, but people like them, doubt they'd grow on their own.

used to work on band and show production lighting. first leds we ever grew under were show lights, long before there were kits or internet knowledge available. there are still people using show tech.

one thing i would add is don't over think it. you can get very spendy chasing the "perfect" light.

cheers.

 

[PurpleGunRack]

one thing i would add is don't over think it. you can get very spendy chasing the "perfect" light.

This thread is exactly about the over thinking of it, so we can do it before buying parts, ie. why spend $150 adding a UV-A rig if the potential return is say only 1%

 

[bluter]

This thread is exactly about the over thinking of it, so we can do it before buying parts, ie. why spend $150 adding a UV-A rig if the potential return is say only 1%

lol ok. keep at it. so far the only i been good at this run is killing plants anyway.

 

[Mayne]

day 65 from seed, 12/12 from start

2-3500KCRI90
2-4000KCRI80
FarRed

A12-12--day65-thr1.png

• Mayne
• May 25, 2018

 

[TTKlaus]

My take is the sun always puts out the full spectrum. She is the big bar all want to mimic. I don't agree using Kelvin to come up with a perfect spectrum. I understand the charts with kelvin and the photo output. But the kelvin lights seem to be heavy in the center and fall of on one or the other extreme (red or blue). If using Kelvin as a measurement, one should supplement in the blue or red spectrums to make it a broader spectrum.

I believe you need a big punch of blue for root and stem foundation when the seedlings first emerge. This takes about 7 days. 24h light during this time. But don't just give them blue, give them all the spectrum you have or can give them. Make sure you also have green spectrum in there, this will give the plant more energy to make photosynthesis more efficient. Green also penetrates into the canopy by reflection of the leaves, it bounces around. Blue and red only hit the tops of leaves and get absorbed there 100%. Green helps to move this energy throughout the plant. Don't over power the plants with umol's, they will start spending energy shedding excess light instead of using energy for photosynthesis.

A light which doesn't get too hot, or has too high a umol output is better, because you can drop it right on top of the canopy. This makes the plants happy, they don't need to stretch, get lot's of dense nodes and broad leaves to aid in light absorption.

There is nothing out there that proves UVB and IR is useful to plant health. It's just myth and hearsay. And it sounds good.

I say, get a light with great overall spectrum, not too powerfull, get between 30 and 40 DLI and keep all the spectrum on all the time, blue,red,green and white. Of course, we see white, the plants don't.

My info is from our direct research with NASA, our research through the University of Wisconsin, our direct plant engineering research, many years of using artificial light for developing seeds (though none of this with Cannabis).
Green light info is from scientist Bruce Bugbee, Utah State University. And much info from Christopher Sloper's book "The LED Grow Book" everybody must read this book!
Here is my spectrum:

Spectrograph.jpg

• TTKlaus
• Mar 26, 2018
• broad spectrum

TTKLaus Spectrograph

All on, all the time.

TTKlaus

 

[TTKlaus]

One other issue which I believe is important. I have a light that puts out a PPFD of 577Umol, in a footprint of 18" x 36". This light consumes 103w to do so. I have increased the drivers output to consume 158w, this increased the PPFD to 661Umol. A nearly 60% increase in power consumption and only a 15% increase in Umol output. Point is, you can spend a lot more energy for little increase in performance. Question is, will the yield and quality of the crop go up by 15% or by 60%? I don't know........

TTKlaus

 

[Mayne]

the higher the cri the better. sun is 100

 

[Mayne]

One other issue which I believe is important. I have a light that puts out a PPFD of 577Umol, in a footprint of 18" x 36". This light consumes 103w to do so. I have increased the drivers output to consume 158w, this increased the PPFD to 661Umol. A nearly 60% increase in power consumption and only a 15% increase in Umol output. Point is, you can spend a lot more energy for little increase in performance. Question is, will the yield and quality of the crop go up by 15% or by 60%? I don't know........

TTKlaus

I think there are alot of myths out there, and really not enough data to consider this or that, this early in the industry of LED.

There are many variables, that needs consideration.

 

[TTKlaus]

I think there are alot of myths out there, and really not enough data to consider this or that, this early in the industry of LED.

There are many variables, that needs consideration.

This goes back to.... Just don't overthink it! We can't improve the sun.
Get a good light source and don't overload the plants with nutrients!

TTKlaus

 

[Purpsmagurps]

4100k is the best all around spectrum,

LOL dont listen to that guy.
3500k is the all around that you want. honestly I like 3000k because I have vertical headroom and it help with Yield not having a bunch of nodes stacked on top of eachother. plus more red in flower wiill give you bigger buds. if you can even go 2700k for flower iif you can afford