LED wavelength/spectrum graph questions

Jahredi · Oct 21, 2019

Hey everyone! First help-seeking post here. Very grateful for this community and all the info

Setting up my first indoor tent grow. Been reading a lot about lights on here and finding a lot of great information.

The one thing I can’t seem to find anywhere is how to read this chart. Mostly curious about how the spectrum measurement impacts plant growth. But also how the various wavelengths do, too.

Here is the graph for a light I’m looking at. What does it tell you?

FWIW, it’s a quantum board style light with Samsung LM301B diodes.

Thank you!

420baby · Oct 22, 2019

440nm and 660nm should be at the peak. Less orange or green is better. Plants need green and red more.

Jahredi · Oct 22, 2019

420baby said:
440nm and 660nm should be at the peak. Less orange or green is better. Plants need green and red more.

Thanks 420baby.

So, is the Spectrum portion of the graph something like the intensity of the wave length?

Is that measurement relative or absolute? For instance, is that a per watt measurement or something?

Do you know what the 1.0=345.065Mw/no means?

I appreciate your help. I have a general understanding of how/which different wavelengths impact plant growth. What I’m really after is exactly how to read this graph and what specific, useful information can be gleaned from it. Thanks!

MIMedGrower · Oct 22, 2019

Jahredi said:
Thanks 420baby.

So, is the Spectrum portion of the graph something like the intensity of the wave length?

Is that measurement relative or absolute? For instance, is that a per watt measurement or something?

Do you know what the 1.0=345.065Mw/no means?

I appreciate your help. I have a general understanding of how/which different wavelengths impact plant growth. What I’m really after is exactly how to read this graph and what specific, useful information can be gleaned from it. Thanks!

Thats the problem with these spectral graphs. They have no standard. They are measuring their own output rather than showing an intensity. Great for marketing. Useless for how much usable light is actually included.

Lumens were actually a better meter to determine how much light you have to work with.

Jahredi · Oct 22, 2019

MIMedGrower said:
Thats the problem with these spectral graphs. They have no standard. They are measuring their own output rather than showing an intensity. Great for marketing. Useless for how much usable light is actually included.

Lumens were actually a better meter to determine how much light you have to work with.

Thanks MIMedGrower! That’s what I suspected. It seems a little vague and relative. I feel like that equation at the top might make it more useful, just trying to figure out how the Mw/nm equation at the top fits in to the picture. I just found another thread on an engineering site that’s explaining the Mw/nm equation as a measurement of light density. I’ll post back if it makes sense to me. Lol.

Aqua Man · Oct 22, 2019

I'm no expert but here is my basic way to look at it. Intensity is more important than spectrum. The amount of photons is more important driving total growth.

Spectrum in my view affects how the plant responds to that light. Eg. Shorter internode distance. But overall growth in terms of tissue would be the same.

I could very well be wrong but with my limited knowledge that's how I see it.

Aqua Man · Oct 22, 2019

Aqua Man said:
I'm no expert but here is my basic way to look at it. Intensity is more important than spectrum. The amount of photons is more important driving total growth.

Spectrum in my view affects how the plant responds to that light. Eg. Shorter internode distance. But overall growth in terms of tissue would be the same.

I could very well be wrong but with my limited knowledge that's how I see it.

Ok I was partially wrong, i still feel intensity is most important but at saturation point spectrum also is very important... I found this and its a great read for all growers.

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Arrays of blue (B, 400−500 nm) and red (R, 600−700 nm) light-emitting diodes (LEDs) used for plant growth applications make visual assessment of plants difficult compared to a broad (white, W) spectrum. Although W LEDs are sometimes used ...

www.ncbi.nlm.nih.gov

Jahredi · Oct 22, 2019

Aqua Man said:
Ok I was partially wrong, i still feel intensity is most important but at saturation point spectrum also is very important... I found this and its a great read for all growers.

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Arrays of blue (B, 400−500 nm) and red (R, 600−700 nm) light-emitting diodes (LEDs) used for plant growth applications make visual assessment of plants difficult compared to a broad (white, W) spectrum. Although W LEDs are sometimes used ...

www.ncbi.nlm.nih.gov

Yes! Thanks Aqua Man This looks like a great article. I can’t wait to read this when I get home tonight. Thank you

Moshmen · Oct 22, 2019

As a first time indoor LED grower myself I don’t fully understand the spectrum yet , I will read the article as well, but what I have learned is the led lighting affects the nutes uptake much differently than the sun. So no matter what light u end up with just be careful with the feeding.

MIMedGrower · Oct 22, 2019

Aqua Man said:
I'm no expert but here is my basic way to look at it. Intensity is more important than spectrum. The amount of photons is more important driving total growth.

Spectrum in my view affects how the plant responds to that light. Eg. Shorter internode distance. But overall growth in terms of tissue would be the same.

I could very well be wrong but with my limited knowledge that's how I see it.

This was proved at the university of michigan with the old metal halide vs. hps argument. Hps won for overall plant growth because of more light output.

Intensity trumps spectrum was the outcome.

Now they are testing discreet colored led diodes and their effect on plant growth.

Proving more blue equals leafier, stouter plants and more red longer stronger branching and more and larger bud sites.

Of course it is much more complicated than i stated.

Im sure they will lead the way to light spectrum plant specific lighting for the ag industry. Well when companies like phillips and samsung get the final info.

madkevin · Oct 22, 2019

I find when looking at each manufacturers light graph they all show them different. There is not standard between them all it makes no sense. They need to standardize the LED industry so the novice can understand their products better.

Jahredi · Oct 22, 2019

Moshmen said:
As a first time indoor LED grower myself I don’t fully understand the spectrum yet , I will read the article as well, but what I have learned is the led lighting affects the nutes uptake much differently than the sun. So no matter what light u end up with just be careful with the feeding.

Interesting Moshmen. Appreciate the insight. How do you find it affects nute uptake?

Now that you mention it, I’d guess they might be less hungry due to a less efficient photosynthesis process. I can’t imagine that even the best Chinese light comes anywhere close to the power of the sun

Jahredi · Oct 22, 2019

V

Aqua Man said:
Ok I was partially wrong, i still feel intensity is most important but at saturation point spectrum also is very important... I found this and its a great read for all growers.

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Arrays of blue (B, 400−500 nm) and red (R, 600−700 nm) light-emitting diodes (LEDs) used for plant growth applications make visual assessment of plants difficult compared to a broad (white, W) spectrum. Although W LEDs are sometimes used ...

www.ncbi.nlm.nih.gov

Very informative article. I’m not quite finished, but it does seem to support your statement that intensity is more critical than spectrum. I thought it was interesting how the Green light was found to penetrate leaves better. And I was surprised by how relatively little of an impact the spectrum has on overall growth. More or less supporting the idea that an intense White light would produce better results than a less intense light of optimal spectrum, definitely making spectrum secondary to intensity.

Thanks so much for sharing that

Jahredi · Oct 22, 2019

MIMedGrower said:
This was proved at the university of michigan with the old metal halide vs. hps argument. Hps won for overall plant growth because of more light output.

Intensity trumps spectrum was the outcome.

Now they are testing discreet colored led diodes and their effect on plant growth.

Proving more blue equals leafier, stouter plants and more red longer stronger branching and more and larger bud sites.

Of course it is much more complicated than i stated.

Im sure they will lead the way to light spectrum plant specific lighting for the ag industry. Well when companies like phillips and samsung get the final info.

Totally. I’m understanding now that it’s really mostly about intensity. And makes sense that choosing a good light means finding one that produces it efficiently.

I found this article explaining PPE helpful:

Plant Lighting Efficiency and Efficacy: μmols per joule - Greenhouse Product News

Plant lighting continues to be a hot topic, especially as light-emitting diode (LED) technology continues to advance. Growers commonly ask which type of lighting technology to purchase. Supplemental lighting using LEDs is usually more efficient, but the initial cost is higher than with...

gpnmag.com

They even explain the processes used to measure intensity. Short and clear.

Homesteader · Oct 23, 2019

The more intense your lights (to a certain point) the more the plants will cycle through nutrients. Certain strains will reach their max quicker than others will. From my experience, using more blue and red light will allow you to peak quicker and create more color in your plants. Certain strains carry a pigment called anthocyanins and others don't. Targeting plants with blue or red that carry this pigment will achieve a much deep color in the finished flower.

Moshmen · Oct 23, 2019

Jahredi said:
Interesting Moshmen. Appreciate the insight. How do you find it affects nute uptake?

Now that you mention it, I’d guess they might be less hungry due to a less efficient photosynthesis process. I can’t imagine that even the best Chinese light comes anywhere close to the power of the sun

well I def not as versed as you guys but I believe the led affects the calcium uptake thru evaporation and ionization from the different spectrums therefore the cal may either evaporate faster or attach itself to other nutrients in the plant which does not let the calcium do its job in the photosynthesis process.
I’m a brand new indoor/auto grower but have done a few grows outdoors and NoTHING even comes close to the power of the

Moshmen · Oct 23, 2019

Jahredi said:
Interesting Moshmen. Appreciate the insight. How do you find it affects nute uptake?

Now that you mention it, I’d guess they might be less hungry due to a less efficient photosynthesis process. I can’t imagine that even the best Chinese light comes anywhere close to the power of the sun

Nutrient uptake probably is not the right verbiage age! Sorry

Homesteader · Oct 23, 2019

Moshmen said:
well I def not as versed as you guys but I believe the led affects the calcium uptake thru evaporation and ionization from the different spectrums therefore the cal may either evaporate faster or attach itself to other nutrients in the plant which does not let the calcium do its job in the photosynthesis process.
I’m a brand new indoor/auto grower but have done a few grows outdoors and NoTHING even comes close to the power of the

Calcium is the main element in the cannabis plant outside of carbon. Calcium is used at the same ratio as other nutrients when intensity of light is increased

Homesteader · Oct 23, 2019

Homesteader said:
Calcium is the main element in the cannabis plant outside of carbon. Calcium is used at the same ratio as other nutrients when intensity of light is increased

I kind of screwed up the wording here. Not AT the same ratio as the other nutrients but the uptake increase is at the same ratio

Aqua Man · Oct 23, 2019

Jahredi said:
V

Very informative article. I’m not quite finished, but it does seem to support your statement that intensity is more critical than spectrum. I thought it was interesting how the Green light was found to penetrate leaves better. And I was surprised by how relatively little of an impact the spectrum has on overall growth. More or less supporting the idea that an intense White light would produce better results than a less intense light of optimal spectrum, definitely making spectrum secondary to intensity.

Thanks so much for sharing that

Kinda makes me think green is a lot more important than I previously thought when reachi

Homesteader said:
The more intense your lights (to a certain point) the more the plants will cycle through nutrients. Certain strains will reach their max quicker than others will. From my experience, using more blue and red light will allow you to peak quicker and create more color in your plants. Certain strains carry a pigment called anthocyanins and others don't. Targeting plants with blue or red that carry this pigment will achieve a much deep color in the finished flower.

Did not know that. Temps also play a role. Anthocyanins don't do as well over 70f like photosynthesis. That's why people drop their temps to bring out color

LED wavelength/spectrum graph questions

LED wavelength/spectrum graph questions

Jahredi

420baby

Jahredi

MIMedGrower

Jahredi

Aqua Man

Aqua Man

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Jahredi

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Moshmen

MIMedGrower

madkevin

Jahredi

Jahredi

Spectral effects of light-emitting diodes on plant growth, visual color quality, and photosynthetic photon efficacy: White versus blue plus red radiation

Jahredi

Plant Lighting Efficiency and Efficacy: μmols per joule - Greenhouse Product News

Homesteader

Moshmen

Moshmen

Homesteader

Homesteader

Aqua Man

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