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A beginners guide to LED's

High-Dro Mephisto

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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.
 

rick-j

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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:
 

L0wbob2017

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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:



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 )



---

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" )



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 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.


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





---

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

(McCree-version)

(DIN-Version from 2018)


---

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:



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.



For a "perfect spectrum" this also means it cant be only one white ( full ) spectrum from seed to harvest.
 

High-Dro Mephisto

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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:



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 )



---

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" )



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 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.


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





---

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

(McCree-version)

(DIN-Version from 2018)


---

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:



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.



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!
 

TheMongol

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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:
 

L0wbob2017

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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 ;)
 

MrOldBoy

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: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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