A beginners guide to LED's

Colorado Dreaming’s Ultimate LED Guide


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So here we are. We decided to grow some weed and all your research shows you the left hand doesn't know what the right is doing. Meanwhile, all you want to want to know is what lights will work best for your grow without damaging your new babies. Well you have have found the right place. Especially if you want just the facts and no bullshit salesman gimmicks or sci-fi scientist talk.


With that being said, there are a few basics we must cover and I will do my best to explain them in layman stoner terms. Also to avoid confusion, discount everything else you have read. You will find most of it aligns with what I have to say however there are some misconceptions which I will address. If you wish to be extra lazy, and want someone else making your decisions vs being informed, feel free to jump down to the Buying guide section.



Science Shit


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So there are some terms you may have heard. Par, PPFD, Quantum Board, Cob , Lumens, Watts and your over here like “Watt” the fuck lol. This is okay. Going in to this shit I felt the same way. I do have a background in optics, including light wavelengths etc. which may have helped me but not much. With that being said let's come to terms.


There are several ways to measure light. But which is right? The short answer, when it comes to horticulture is PPFD, and I would never buy from a lighting company/distributor that does not supply a full ppfd plotting map. ( more on this latter) Let me explain why by breaking down the bullshit others throw at you. Let's start with laymen definitions of the terms.




  • Wavelength- This is the color of the light. Plants like different colors of lights for different reasons.

  • Temperature - This is a fancy way of pointing out which group of wavelength a light source is using.

  • PAR - This is how much of that color light (usable) a lightsource is putting off. If our light is the sun. This is how much radiation its putting off.

  • Lumens - This is how bright the light source is. We don't care at all about this one as we are not trying to see, but rather, grow weed.

  • Watt - Look at this one as a measurement of how much electric does the light source use. This one may be useful if we are measuring energy efficiency. But when it comes to LEDS they are designed to be efficient. So unless we are counting pennies we can pretty much ignore this one as well. Electricity doesn't grow plants!

  • Quantum Board - is basically a board with a series of high performance LED’s on it. The advantage of these is they are able to deliver a more uniform coverage area.

  • COB - Is short for chips on board. Look at this as if we took a quantum board’s LEDs and push them all together in a tight spot. These are a great choice because they do a great job at growing and are relatively inexpensive. The disadvantage is if you are growing several plants over a large area, it will take several to provide optimal coverage.

  • PPFD - This is the measurement of how much of that awesome light is hitting your beautiful plants that they can use to GROW! That's right. This is the one that really matters at the end of the day.



3 Rules on choosing lights


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Okay, now that we have most of that out the way you are probably wondering what does all this mean or how can I use any of this information to buy the light I want? Well we can use this info to provide a few simple ground rules for shopping for a light. Which I will lay out and then briefly explain.



  • Ignore watts! 1W, 3W, 5W…. 150 watts from the wall. Doesn’t mean shit!

Like I mentioned before, electric doesnt grow plants, light does. So why would we care how much electric our lights are using unless we counting pennies. Don't be fooled by anyone selling you on the watts of a light.


  • All lights provide the same PAR and Temperature options. There isn't a magical formula .

Don't be tricked by companies claiming they have the perfect “Spectrum” of lighting. Or that their light mimics the sun. This is all gimmick shit. In simple terms you want something around 3000k ( More red wavelength) and 4000K (More Blue). To make it supper easy go with 3500K and you can't go wrong.


  • Look for a Plot map of PPFD ranges. Not just a single PPFD number or PAR number.

Whoa, whoa, whoa. I thought you said this was going to be simple? Relax. It is. Basically a lot of companies will give you “features” laid out in list format. This is great for a quick comparison. But at the end of the day we want to make sure we got adequate coverage for all our plants. We will get to what numbers to look for in a minute. But for now, just know that a bigger number is better. Look below.

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This above is taking from a Quantum LED board. Notice how the numbers in the middle are highest and get lower almost uniformly as we get further away from the center. This is very typical of a quantum board and as I mentioned above they may be best for covering a large area.



The Picture below is a PPFD plot a COB. Notice the higher numbers in the middle but see how the numbers quickly drop off on the edges. ( with the exception on a line across the middle due to refractors, which are not covered here.) This makes COBs idea for growing in tight spaces or only 1 or 2 plants per light.

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Still with me? Alright fantastic. So far we have covered; weeding through science lingo, what not to buy or what to look out for, and started to look at what you should be looking for. This next part we will talk more specific in numbers and I will make some recommendations on some actual lights.




Buying guide


So let us get right into it. First thing is first, there isn’t a “one size fits” all. Errrr. I hate this expression because anytime I hear it I know shit isnt going to be as simple as I want it to be. It doesn't have to be complicated either though. Because there are enough universal rules that we can safely pick a few lights that will fit almost everybody's needs.

If you are just joining us and skipped “science shit” just relax for a minute, don't think to hard and we will get into recommendations soon enough.


  • We want a PPFD around 600-800 (optimal) for growing weed.

If we look back at the examples of the PPFD plots from before we can see now, taking into account plant space, the limitations of the 2 style of lights. Now these would be ideal conditions and it is very common to be below these ranges in parts of your grow space. So don't fret if your doing math on some lights you've seen and are now thinking you need 3 of them and the toll it’s going to have on your wallet. PPFD ranges even as low as 200 will grow plants just fine. You also can add additional lighting and quickly get where you want from where the light overlaps.


  • What if we are over that?

Well at some point we reach like a “light saturation level” Where the plants will stop using it. This is somewhere between 800-1000 PPFD typically. Depending on your grow environment if you can supplement CO2. Which a lot of growers do, you can actually get your plants to use numbers as high as 1500. But we are not going to get into all that. Just know that your not going to hurt your plants, but you are wasting energy by going for any more than that.


  • Buy a white light!

Im serious people. The age of the “Blurple” is over. There is still a lot of science to be found out about how plants use light. But just know they use all of it, if you are only giving your plants blue and red they are missing key components needed to grow optimal. Buy a full spectrum white light and if you want you can supplement it with narrow spectrum lighting. I’m not going to tackle the subject of that in this guide quite yet. Maybe down the rode.




This about covers most of the basics and the main mistakes and misconception when it comes to buying a LED light. At least that I can think of at this time. I will definitely update and provision this guide as time goes on. But I really wanted something out there like this since I spent weeks reading science articles and studies just to figure out some very basic shit it seems. Below are a few of my recommendations based on your grow areas for LEDS. I have no ties to any of these companies. And this isnt a comparison. I encourage you to do your own research and share any other awesome manufactures you may find. I hope you have enjoyed this article and I look forward to the feedback!



Update 2020

I really wanted to come back to this and provide some more useful information but have not had time between work and school. However I did come across a nice video on YouTube that does a good job at illustrating some of the items covered in this guide so I wanted to share it as a supplement as I know some people are more visual learners.

 
Last edited:
Nice job with the write up, CD!

:slap:

There will always be room for a Blurple in veg for me, though. I read somewhere where someone said Blurple provides something magical during the veg phase, and I must say I agree with them! Cobs with UVB for flowering for sure, though.
Thank you for the love. And there is absoultly nothing wrong with having a blurple . lol. There is defintly a very good use for narrow band lighting as a supplement. Im going to add sections later down the road on it for sure. Especially the use of the UV wavelengths. Nothing like forcing mutations and self defense mechanisms to improve your end product.
 
Absolutely. There is lots of great info on this site amd it has helped me out tremendously. Those girls are looking nice. You close to harvest?
Yes, with lots of help, I just chopped the tops off all 3 girls, waiting for the rest to catch up. This is such a great hobby, and believe me, I need those good relaxing meds. Thanks again----:jointman:
 
Please dont take any of this offensive!

First of all, plants use light for waaay more than just photosynthesis, therefore a varying white (full) spectrum is a must for optimal results.

Wavelengths:

Sinus-visualisation.gif


Light is a photon that acts like a wave. Imagine a sinus wave like this. The faster this happens the higher its frequency is.
A high frequency results in a shorter wavelength ( for example ~460nm - blue ). The lower the frequency the longer the wavelength ( for example ~640nm - red )

800px-Electromagnetic_spectrum_-de_c.svg.png


---

Humans can see light in a range of about 380 - 780nm. Also the human eye can see some colors better than others and this also depends on the day or night cycle.
(Theoretically you can name this the human "action spectrum" )

800px-Spectral_luminous_efficacy_1200x1400_wcols_de.png


The big one ( K' ) is called scotopic and describes the average spectral sensitivity of human visual perception of brightness at night ( at night you are more sensitive for blue - maybe some of you know the bluefilter of your smartphone, thats why it even exists )
The small one ( K ) is called photopic and describes the same for daytime ( you are more sensitive to green )

Every spectrum ( this should better be called "spectral power distribution" ) you can see in a datasheet is normalized for this curve, so you know what a human eye would see at the day because it was invented for artificial working lights.
This results in the fact, that a spectrum in a LED-datasheet is not what plants see.

---

Back in the time it was thought that plants only use light within the range of 400 - 700nm. Therefore they invented the so called PAR-spectrum. ( photosynthetic active radiation )

PAR-photonen-effizienz.png


PAR itself does not have any unit and is only a curve that sets the efficiency on 1 for a range of 400 - 700nm. This also means that every photon is equal in terms of photosynthesis ( which is not the case ).
To measure this radiation the so called photosynthetic photon flux ( PPF ) is used and it has the unit µmol/s.

If you have a PAR-value for a specific lightsource this just tells you the sum of all photons within the range of 400 - 700nm that get emitted in 1 second.

In the last 2 years a new measurement is coming in some horticulture datasheets. It is called photobiological active radiation ( PBAR ). It is basically the same as PAR but with a range from 200 - 800nm.
Because the PPF-value of a lightsource does not say much about what will hit the plants at a certain distance and McCree found out that photosynthesis is a quantum process which depends more on the amount of incoming photons than on the wavelength ( color ), the photosynthetic photon flux density ( PPFD ) was created. It is a measurement of how many photons hit one squaremeter. Its unit is µmol/(m²*s).

About the range you should aim for it is about 400 - 600 µmol/(m²*s) if you dont live in a very industrial part of your city where the ambient CO2 levels are higher. For effective usage of more light you should be about 600ppm CO2.

---

To be able to compare photons of different wavelengths these have to be equalized in terms of energy. Like aforementioned "blue" light does have more energy than "red" light.
Therefore you take 1 Joule of energy and calculate how many photons of a certain wavelength you can produce with it. The results get normalized by the wavelength with the lowest energy which is 700nm.

PAR-umrechnung.png

You can see that the energy of a photon with a wavelength of 700nm would be close to 60% of the energy of a photon with a wavelength of 400nm. This curve is also called the "PAR spectral response".

---




Since PAR, PBAR, PPF or PPFD all assume that every photon is equal in terms of photosynthesis ( which it isnt ) the so called Yield photon flux ( YPF ) was invented. It has the range from 360 - 760nm.
This takes the photosynthetic reaction of the plant depending on the energy of the incoming photon ( normalized with the PAR spectral response ).
You also can call this the action spectrum.

Over the time there were created some standards/DINs/ISOs ( whatever you wanna call them ). [ McCree, Inada, Tazawa, DIN 5031-10, Dodillet ]
McCree and Inada made the start with a massive data-collection which has been used years later by Tazawa to make some nice graphs

YPF-alt-Inada.png
YPF-alt-McCree.png

YPF-tazawa-1999.png



---

To make the difference between PPF and YPF a bit more clearer

(McCree-version)
PPF-YPF-alt.png

(DIN-Version from 2018)
PPF-YPF-neu.png


---

So after all that you can now take the famous average action spectrum and try to adopt it to one specific planttype that changes its action spectrum depending on age and veg/bloom stage. ( hint )
But first you have to take a spectrum of a LED, renormalize it with the action spectrum of humans at daylight and normalize it back with the action spectrum for plants.
Then you know how the average tested plants would see your light. With this you also could calculate how effective it would be compared to a theoretically perfect spectrum.

To see the difference between the datasheet and what plants see i made a post a few months ago. Here is the graphic from that post:

6sF7OUJ.png


The dashed lines are from the datasheet and the not-dashed lines are what the plant would actually see.

---

Coming to that hint i made before.
If someone claims he has a light that is optimized for a specific planttype and it has only 3 possible spectra ( veg, bloom, veg + bloom ) it most likely is not optimized.
Since the incoming light spectrum varies within the day and the year it basically would need a lot of different spectra with the right intensities.

UVBArtikelBild5.gif


For a "perfect spectrum" this also means it cant be only one white ( full ) spectrum from seed to harvest.
 
Please dont take any of this offensive!

First of all, plants use light for waaay more than just photosynthesis, therefore a varying white (full) spectrum is a must for optimal results.

Wavelengths:

Sinus-visualisation.gif


Light is a photon that acts like a wave. Imagine a sinus wave like this. The faster this happens the higher its frequency is.
A high frequency results in a shorter wavelength ( for example ~460nm - blue ). The lower the frequency the longer the wavelength ( for example ~640nm - red )

800px-Electromagnetic_spectrum_-de_c.svg.png


---

Humans can see light in a range of about 380 - 780nm. Also the human eye can see some colors better than others and this also depends on the day or night cycle.
(Theoretically you can name this the human "action spectrum" )

800px-Spectral_luminous_efficacy_1200x1400_wcols_de.png


The big one ( K' ) is called scotopic and describes the average spectral sensitivity of human visual perception of brightness at night ( at night you are more sensitive for blue - maybe some of you know the bluefilter of your smartphone, thats why it even exists )
The small one ( K ) is called photopic and describes the same for daytime ( you are more sensitive to green )

Every spectrum ( this should better be called "spectral power distribution" ) you can see in a datasheet is normalized for this curve, so you know what a human eye would see at the day because it was invented for artificial working lights.
This results in the fact, that a spectrum in a LED-datasheet is not what plants see.

---

Back in the time it was thought that plants only use light within the range of 400 - 700nm. Therefore they invented the so called PAR-spectrum. ( photosynthetic active radiation )

PAR-photonen-effizienz.png


PAR itself does not have any unit and is only a curve that sets the efficiency on 1 for a range of 400 - 700nm. This also means that every photon is equal in terms of photosynthesis ( which is not the case ).
To measure this radiation the so called photosynthetic photon flux ( PPF ) is used and it has the unit µmol/s.

If you have a PAR-value for a specific lightsource this just tells you the sum of all photons within the range of 400 - 700nm that get emitted in 1 second.

In the last 2 years a new measurement is coming in some horticulture datasheets. It is called photobiological active radiation ( PBAR ). It is basically the same as PAR but with a range from 200 - 800nm.
Because the PPF-value of a lightsource does not say much about what will hit the plants at a certain distance and McCree found out that photosynthesis is a quantum process which depends more on the amount of incoming photons than on the wavelength ( color ), the photosynthetic photon flux density ( PPFD ) was created. It is a measurement of how many photons hit one squaremeter. Its unit is µmol/(m²*s).

About the range you should aim for it is about 400 - 600 µmol/(m²*s) if you dont live in a very industrial part of your city where the ambient CO2 levels are higher. For effective usage of more light you should be about 600ppm CO2.

---

To be able to compare photons of different wavelengths these have to be equalized in terms of energy. Like aforementioned "blue" light does have more energy than "red" light.
Therefore you take 1 Joule of energy and calculate how many photons of a certain wavelength you can produce with it. The results get normalized by the wavelength with the lowest energy which is 700nm.

PAR-umrechnung.png

You can see that the energy of a photon with a wavelength of 700nm would be close to 60% of the energy of a photon with a wavelength of 400nm. This curve is also called the "PAR spectral response".

---




Since PAR, PBAR, PPF or PPFD all assume that every photon is equal in terms of photosynthesis ( which it isnt ) the so called Yield photon flux ( YPF ) was invented. It has the range from 360 - 760nm.
This takes the photosynthetic reaction of the plant depending on the energy of the incoming photon ( normalized with the PAR spectral response ).
You also can call this the action spectrum.

Over the time there were created some standards/DINs/ISOs ( whatever you wanna call them ). [ McCree, Inada, Tazawa, DIN 5031-10, Dodillet ]
McCree and Inada made the start with a massive data-collection which has been used years later by Tazawa to make some nice graphs

YPF-alt-Inada.png
YPF-alt-McCree.png

YPF-tazawa-1999.png



---

To make the difference between PPF and YPF a bit more clearer

(McCree-version)
PPF-YPF-alt.png

(DIN-Version from 2018)
PPF-YPF-neu.png


---

So after all that you can now take the famous average action spectrum and try to adopt it to one specific planttype that changes its action spectrum depending on age and veg/bloom stage. ( hint )
But first you have to take a spectrum of a LED, renormalize it with the action spectrum of humans at daylight and normalize it back with the action spectrum for plants.
Then you know how the average tested plants would see your light. With this you also could calculate how effective it would be compared to a theoretically perfect spectrum.

To see the difference between the datasheet and what plants see i made a post a few months ago. Here is the graphic from that post:

6sF7OUJ.png


The dashed lines are from the datasheet and the not-dashed lines are what the plant would actually see.

---

Coming to that hint i made before.
If someone claims he has a light that is optimized for a specific planttype and it has only 3 possible spectra ( veg, bloom, veg + bloom ) it most likely is not optimized.
Since the incoming light spectrum varies within the day and the year it basically would need a lot of different spectra with the right intensities.

UVBArtikelBild5.gif


For a "perfect spectrum" this also means it cant be only one white ( full ) spectrum from seed to harvest.
Lol I love it! I spent a lot of time reading studies just like that before I wrote this guide. Thats the whole reason I felt it was needed. Thanks for sharing that. Im going to thread mark it in case anyone wants a more in depth look. I plan to add some sections later on supplementing uv and infared wavelengths at some point. Awesome read mate!
 
So......his Highness @L0wbob2017 was pleased again to let some foot prints on canna earth:crying: well done buddy and others i haven't expected from you :thumbsup:, but 1 thing you have to explain....why u 9 am already like this :coffee: wile university is off till march for you?:shrug:bored again?....had to tickle you rep kitty for your post:pass:
 
So......his Highness @L0wbob2017 was pleased again to let some foot prints on canna earth:crying: well done buddy and others i haven't expected from you :thumbsup:, but 1 thing you have to explain....why u 9 am already like this :coffee: wile university is off till march for you?:shrug:bored again?....had to tickle you rep kitty for your post:pass:

well, you tagged me and i had the time and was in the mood for it, so i thought i am going to answer on a scientific level. Since i had to learn all that a long time ago, i thought it might contribute. I had the feeling that there were missing some important infos and explainations.

Yesterday was a bit late so i left out some topics. Gonna edit later when i have time again ;)
 
:worship:
I would like to attribute a portion of the success I’m experiencing growing autoflowers to the fine folks like @ColoradoDreaming420 .... it’s info like this shared that makes us all better .... I think it’s @Vapo69 - another who gives freely his knowledge .... that says “imore I know the better I grow” .....

Best of Grows to All.
:frog:
 
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