Light ???

If you look at the absorbance curve of chlorophyll a and b, you'll notice that blue and red are absorbed the most and absorbed the most is another way of saying penetrated the least.

Far-red (700nm-800nm) and spectral yellow have poor absorption by chlorophyll, and thus very good penetration.

Anything that gets absorbed well has poor penetration.

Uncle Ben said:

Is it my understanding that only red and far red light is capable of penetrating the canopy.

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I came up with it myself after watching all the red+blue led grows fail so hard and after the gro-lux tubes seemed to have the same negative effects on flowering. NO MATTER HOW MUCH LIGHT WAS USED.

660nm red may be the highest 'quality' color in that it causes the most amount of phytochrome to be in Pfr state (85% in the active form), but it's an oversimplication to say that high Pfr good, low Pfr bad.

When people started showing such amazing results with 3000k leds, it vindicated my theory that yellow light was the key that was missing. Now I'm trying to prove the theory wrong rather than collecting evidence to see if it's right.

The real question you've gotta ask yourself is if yellow is so bad, what is it that makes HPS so good?? (not what makes it so bad)

natro.hydro said:

Please dont take this as me calling bs.
But I would really like to know where you read that, if it is some common law of plant growth than nevermind, but I had never heard yellow was more effective so if you have a good link to read on that would be appreciated

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think of the difference between UV-A and UV-B and your eyes. Even though UV-B photons are more damaging, they are unlikely to damage your retina, because they will never penetrate your cornea. Instead, UV-B will turn your cornea gray.

UV-A has poor absorbance in the cornea and thus it's more likely it will end up in the retina.

PENETRATION IS THE INVERSE OF ABSORBANCE!

I just love information.....

This is exactly what LED growers have been discovering over the last few years. One of the issues with R+B lighting is that it's impossible to bombard the plant with enough sheer power in R+B alone without burning the top layer of canopy with radiation. Think of yellow like the microwave while red is like a cast iron pan. You need both colors to hit all layers of canopy and to properly calibrate shade avoidance.

It would be like trying to sear a large roast all the way to medium rare on the cast iron on high. Great at cooking the outside, but in order to get enough power to cook the inside, you'll end up with an inch of black.

It doesn't matter if you get the most powerful red and blue leds in the world.. you won't beat the results of 3000k 80CRI warm white leds using only red and blue alone. I've yet to see it. Until I do, I'm led to conclude that the spectrum of 3000k warm white leds is superior for producing buds to 2 narrow bands centered at 660nm and 440nm.

Keep in mind that my theories are based on what I see with my own eyes. I used to think what you guys think about red and blue, but now think something else!! What I'm currently seeing is that red is food for the top, and yellow is food for the bottom.

RM3 said:

Pretty sure it is not the yellow light IMO (based on all I have read) the reason that HPS works is the sheer power of bombarded photons and that the plants adapt to it. With recent technical advances in LED lights it seems most greenhouses are switching to em as seen in that vid that I posted

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Sorry to steal this thread, but keep in mind that different plant species have different spectrum requirements.

Shade plants like lettuce will do just fine with only R+B, because they have no shade avoidance effect and are not tall enough that the top layer blocks the lower layers of leaves from absorbing red. Lettuce is the low hanging fruit for R+B, and it's what you've been seeing the mainstream convert over to LED for already.

Lettuce also benefits from the 660nm red in that lettuce seeds like it for germinating. (darkness or 730nm will inhibit germination)

Throw theory out the window. People have been trying all this crap for the last decade now that high power led arrays make it cheap to do these experiments. White kicks ass for flowering weed, and R+B sucks, thus I can only conclude that it kicks ass BECAUSE it's white, not in spite of it, and that R+B sucks because it's not white. The plant uses all wavelengths between 400nm and 700nm to produce photosynthesis, and tall sun-loving plants like all the wavelengths.

churchhaze said:

Sorry to steal this thread, but keep in mind that different plant species have different spectrum requirements.

Shade plants like lettuce will do just fine with only R+B, because they have no shade avoidance effect and are not tall enough that the top layer blocks the lower layers of leaves from absorbing red. Lettuce is the low hanging fruit for R+B, and it's what you've been seeing the mainstream convert over to LED for already.

Lettuce also benefits from the 660nm red in that lettuce seeds like it for germinating. (darkness or 730nm will inhibit germination)

Throw theory out the window. People have been trying all this crap for the last decade now that high power led arrays make it cheap to do these experiments. White kicks ass for flowering weed, and R+B sucks, thus I can only conclude that it kicks ass BECAUSE it's white, not in spite of it, and that R+B sucks because it's not white. The plant uses all wavelengths between 400nm and 700nm to produce photosynthesis, and tall sun-loving plants like all the wavelengths.

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I do not see your input as stealing the thread, rather I see it as adding to the conversation. While we don't agree on everything, I believe we do agree on most things

IE: when I played with LED lights I went ALL white ( in fact I just posted the results of that test in my ICMAG thread) and if I was to play again I would go in the 4100K region with something like these ,,,
https://www.energyavenue.com/LED-Light-Bulbs/PAR38-LED-Lamps?start=0&display=24
I tend to play with things that most would not consider LOL

For those interested in the actual math, theories and laws there is a very good book on photosynthesis here ,,,,,

http://www.life.illinois.edu/govindjee/photosynBook/

And yet another good read on the subject here ,,,

http://www.controlledenvironments.org/Light1994Conf/1_5_Bugbee/Bugbee text.htm

For those that wanna go crazy with it here is a google related search with all kinds of stuff

https://www.google.com/search?biw=1024&bih=646&q=related:www.life.illinois.edu/govindjee/photosynBook/Chapter10.pdf+photon+penetration+vs+absorbance+in+plants&tbo=1&sa=X&ei=nQu8VKjBHcSbyASq74GYDA&ved=0CEkQHzAG

Photosynthesis is only one half of the story.

Plants, like animals, have color vision that is independent from the pigments used to produce photosynthesis. Instead of 3 cones that excite the brain electrically, they use 2 complementary pigments, phytochrome-R (the inactive form) and phytochrome-FR (the active form). When one form absorbs a photon, it becomes the other form.



Conveniently (or coincidentally), the absorbance peak of chlorophyll a and the absorbance peak of Pr happen to line up perfectly. This allows leaves to see how "good" the light is, where 660nm is "perfect", and 730nm is "completely shaded". A 660nm light source will cause %Pfr (percent of total phytochromes in Pfr form) to reach %85. a 730nm source will cause it to reach near 0%.

When a lower branch has a low %Pfr, it stretches until it sees a higher %Pfr.

The correlation between %Pfr and stretch rate is logarithmic. You will get exponentially more stretch by introducing far-red to a grow.



If you want proof that 730nm causes stretch, get some high powered 730nm leds (about 20W worth) and introduce them to your grow, and you will no longer doubt this. After a few days, you will be convinced that the stretch is insane just by adding light.

On the other hand, a very small amount of 730nm in your light source is good, because it tells the lower branches with red filtered out to stretch until it gets to canopy level. It's a signal!

Yellow also causes %Pfr to converge lower than red and penetrates well, so it has a similar shade avoidance calibrating effect. As a bonus, any yellow absorbed by lower leaves can be used to produce photosynthesis!

churchhaze said:

Photosynthesis is only one half of the story.

Plants, like animals, have color vision that is independent from the pigments used to produce photosynthesis. Instead of 3 cones that excite the brain electrically, they use 2 complementary pigments, phytochrome-R (the inactive form) and phytochrome-FR (the active form). When one form absorbs a photon, it becomes the other form.

Conveniently (or coincidentally), the absorbance peak of chlorophyll a and the absorbance peak of Pr happen to line up perfectly. This allows leaves to see how "good" the light is, where 660nm is "perfect", and 730nm is "completely shaded". A 660nm light source will cause %Pfr (percent of total phytochromes in Pfr form) to reach %85. a 730nm source will cause it to reach near 0%.

When a lower branch has a low %Pfr, it stretches until it sees a higher %Pfr.

The correlation between %Pfr and stretch rate is logarithmic. You will get exponentially more stretch by introducing far-red to a grow.

If you want proof that 730nm causes stretch, get some high powered 730nm leds (about 20W worth) and introduce them to your grow, and you will no longer doubt this. After a few days, you will be convinced that the stretch is insane just by adding light.

On the other hand, a very small amount of 730nm in your light source is good, because it tells the lower branches with red filtered out to stretch until it gets to canopy level. It's a signal!

Yellow also causes %Pfr to converge lower than red and penetrates well, so it has a similar shade avoidance calibrating effect. As a bonus, any yellow absorbed by lower leaves can be used to produce photosynthesis!

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AFTER READING THE YELLOW SPEC THEORY SEEMS PLAUSABLE, what led would u recomend or would u say stick w hps and mh? do led's put out anything with a spectrum equal to an hps, not only in penetration, but square meter? i believe all the links pining hid's vs led's are geared for the led by using a 4x4 area wile using a 1000 watt hps which can cover double the area of the led its up against..if they want to do a true comparison put both lights in a 5x6 area,,i believe in thsat area the hps would beat out any led..

Look into cree cxa3070 or vero 18 (or any of the vero series).

3000k 80cri for both is very close to HPS spectrum, but has a R:FR of about 6:1 rather than HPS 2:1, so it's not entirely the same.

In the long run, I think everyone will be using the 3000k 80cri vero or cxa. It's slightly more efficient than HPS, with a much higher startup cost, and since driving them at lower currents gets slightly higher efficiency, there's a direct correlation between start up cost and efficiency, with very hard diminishing returns. Efficiency with the cxa3070 3000k 80cri AB bin is as high as 50% when driven at 350mA, but most DIYers run them at 1400mA, which has an efficiency closer to 40%.

The performance is definitely there though if you're willing to shell out the cash up front. Most of the DIYers in the LED section are using 3000k or 3500k whites.

The efficiency of a fresh 600W HPS lamp is about 35%, which is pretty hard to compete with. Vero 18 driven at 700mA is about 38% efficient... It's not going to eliminate heat like a lot of people think. The other 62% is dumped out as heat, and realistically, so is the 38% output as light. Where you think that's going, light heaven? The output from the cobs is dangerously strong and can start fires if you're not careful. Light is heat. Most of the light hitting the plant is actually just going to heat it up. Very little of that energy is used to produce sugars.

Of course there are some other advantages of cobs over HPS. The output does not decrease over time and require replacement nearly as fast as HPS. 35% is only for a fresh HPS lamp. It goes down to about 30% when it's time for replacement. The cobs also have a 120 degree cone pattern, which means they don't need a reflector, which some light is lost reflecting.

It's a very tough call whether it's worth replacing HPS with cxa3070 or vero, especially if you have everything setup already.

Here's my DIY vero 18 3500k 80cri setup driven at 700mA. (20W dissipated per cob). Lots of people have been going this route because it's easier than wiring and mounting individual, smaller, leds. I have 3 of these hanging in a 4'x2' tent.

TheChemist77 said:

AFTER READING THE YELLOW SPEC THEORY SEEMS PLAUSABLE, what led would u recomend or would u say stick w hps and mh? do led's put out anything with a spectrum equal to an hps, not only in penetration, but square meter? i believe all the links pining hid's vs led's are geared for the led by using a 4x4 area wile using a 1000 watt hps which can cover double the area of the led its up against..if they want to do a true comparison put both lights in a 5x6 area,,i believe in thsat area the hps would beat out any led..

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churchhaze said:

Look into cree cxa3070 or vero 18 (or any of the vero series).

3000k 80cri for both is very close to HPS spectrum, but has a R:FR of about 6:1 rather than HPS 2:1, so it's not entirely the same.

In the long run, I think everyone will be using the 3000k 80cri vero or cxa. It's slightly more efficient than HPS, with a much higher startup cost, and since driving them at lower currents gets slightly higher efficiency, there's a direct correlation between start up cost and efficiency, with very hard diminishing returns. Efficiency with the cxa3070 3000k 80cri AB bin is as high as 50% when driven at 350mA, but most DIYers run them at 1400mA, which has an efficiency closer to 40%.

The performance is definitely there though if you're willing to shell out the cash up front. Most of the DIYers in the LED section are using 3000k or 3500k whites.

The efficiency of a fresh 600W HPS lamp is about 35%, which is pretty hard to compete with. Vero 18 driven at 700mA is about 38% efficient... It's not going to eliminate heat like a lot of people think. The other 62% is dumped out as heat, and realistically, so is the 38% output as light. Where you think that's going, light heaven? The output from the cobs is dangerously strong and can start fires if you're not careful. Light is heat. Most of the light hitting the plant is actually just going to heat it up. Very little of that energy is used to produce sugars.

Of course there are some other advantages of cobs over HPS. The output does not decrease over time and require replacement nearly as fast as HPS. 35% is only for a fresh HPS lamp. It goes down to about 30% when it's time for replacement. The cobs also have a 120 degree cone pattern, which means they don't need a reflector, which some light is lost reflecting.

It's a very tough call whether it's worth replacing HPS with cxa3070 or vero, especially if you have everything setup already.

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THANKS FOR THE INFO!! ILL DO SOME RESEARCH, BUT DAMN LED'S ARE SO EXPENSIVE TO SWITCH

RM3 said:

Pretty sure it is not the yellow light IMO (based on all I have read) the reason that HPS works is the sheer power of bombarded photons and that the plants adapt to it. With recent technical advances in LED lights it seems most greenhouses are switching to em as seen in that vid that I posted, but here is yet another example,,,

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I don't know where he bought this light but that spectrum doesn't look anything like the spectral analysis of HPS I've ever seen. I posted an Osram back on page 7. https://www.rollitup.org/t/light.853779/page-7

RM3 said:

What are we investigating? not sure I'm following. I would put temp & humidity above light in importance of tweaking but light is very much needed, I simply don't consider it the #1 item in terms of tools to use to improve. However I use T5's so I can tweak the spectrum and have it be nothing but what plants require

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My first question would be this: have you done this test with HPS and T5's to compare actual results? My second question is: have you done this test with Sativa's and Indica's, where there are completely different stretch modes in flowering.

Guitar Man said:

My first question would be this: have you done this test with HPS and T5's to compare actual results? My second question is: have you done this test with Sativa's and Indica's, where there are completely different stretch modes in flowering.

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What test ???

RM3 said:

What test ???

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Growing out the same Strain using HPS and Floro lights to see if the overall results of harvest are different?

Guitar Man said:

Growing out the same Strain using HPS and Floro lights to see if the overall results of harvest are different?

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I do not (nor will I ever) own an HPS light, but there is a grower doing a test with one of my strains that just started, he has T5, CMH & HPS and is gonna do clones under each.

Here is what I already know to be true, the results will be that the HPS yields better and the plants under the T5 will be more potent or better quality. This grower doing the test has already posted that with a different strain (C99, I believe)

RM3 said:

I do not (nor will I ever) own an HPS light, but there is a grower doing a test with one of my strains that just started, he has T5, CMH & HPS and is gonna do clones under each.

Here is what I already know to be true, the results will be that the HPS yields better and the plants under the T5 will be more potent or better quality. This grower doing the test has already posted that with a different strain (C99, I believe)

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Then how come your post is focused on the subject of Light, but you've never proven that HPS is good or bad via your own experience?