The Perfect Spectrum *Graphs*

[runner's high]

Almost all lights used to grow marijuana are inefficient. They use a lot of energy to create light that is useless and even harmful to the plant. This isn't the lights' fault; most lights are designed to emit bright, semi-natural looking light and they are generally good at this. The problem is the idea that this light is right for growing marijuana.

This is my personal summary of some pretty basic info I've collected. If you already know about this stuff just skip to my second diagram.

Marijuana uses only a few wavelengths of the wide spectrum of light and it rejects the rest; it doesn't even absorb most natural sunlight. Marijuana's specific absorption spectrum requires a specific emission spectrum and, despite our general failure to meet it efficiently, we know exactly what it is. The plant's color pigments absorb mainly high red (around 670nm) and blue (around 440) wavelengths, and very little in between. (In fact, plants appear green because they don't absorb green light for photosynthesis and it is reflected.) And light outside the visible spectrum is also useless and even potentially damaging, like ultraviolent light (< 400nm) and infrared light (> 680).



Above is a typical plant absorption spectrum--the full range of wavelengths of light it absorbs. The perfect emission spectrum of a grow light must be the exact same in order to fill the needs of the plant without wasting energy on unneeded wavelengths.

What lights do we use to get the best spectrum?

There are a number of lights we don't use at all, light incandescent lights and black lights, because their spectra are poor fits. Other lights, namely fluorescent tubes, CFLs, metal halide and high pressure sodium lights have better reputations for a reason. Look at their spectrums; they cover most of marijuana's spectrum but, unfortunately, they all additionally emit a lot of unneeded light. Flouresent tubes and CFLs do not emit as much useless light, so they are often termed "more efficient". Metal halide and high pressure sodium, on the other hand, are less efficient but they more fully cover the desired spectrum. This is where most growers end their search, with a choice between more efficient, cheaper lights and more powerful, less efficient ones. A tradeoff.

But LEDs are a new contender, a wildcard, since LED technology is still developing and LEDs are considerably more diverse in wavelength, watts, and lumens than traditional grow lights. LEDs are generally very efficient and they tend to emit very limited ranges of light. While LEDs are becoming increasingly popular most LED lights are poor fits for marijuana's spectrum. These lights are the "best fit" for marijuana but they are all very expensive. So we hit another roadlock.

OK, something affordable?

Yes, I think I've just found it. I've looked at the emission spectra for most commercial lights and two of these lights offer an almost perfect fit for their range of wavelengths: red and blue flouresent tubes. Here I superimposed the red-blue light emission spectrum over the plant's absorption spectrum.



This is the best fit I've ever seen. There's no UV, no IR, and almost no green. These two relatively cheap, efficient lights combine to cover most of marijuana's preferred spectrum.

There must be disadvantages...

As you can see, the blue portion of the spectrum is a little weak. This isn't actually a problem because we don't need the same number of red/blue lights. Just get more blue lights than red ones.

One disadvantage with all grow lights that I should have mentioned is that marijuana's preferred wavelength actually changes as marijuana matures. The blue range is more important for vegitating and the red range is more important for flowering, this forces some people to alternative between completely different light sources, but the red-blue method is much easier to deal with--just appropriately replace red bulbs with blue ones or vice versa.

So what do you guys think?

Is there anyone out there who has tried or is willing to try red and blue fluorescent bulbs? The stats I cited were from Philips 36W bulbs but I imagine other companies make them as well. I can see no reason why they would not work, but unfortunately I am not in a place where I can grow. I've put a good deal of thought into this and I want to hear what you guys think.

[Red Eye]

Lots of people use fluorescents, or CFLs to grow their crops. i have also seen people use LEDs to grow their plants. The main problem with these types of lights is their low penetration. These lights arent intense enough to penetrate very far. This leads to people training(tying down, SCROG, or LST) their plants to recieve as much light to the budsites as possible. These lights also need to be placed much closer to the plant than traditional HIDs. THis is ok because they create much less heat also.

LEDs show the ability to create the most focused PAR lighting of any type of lighting. But, these have yet to be made commercially available. And they are the weakest in terms of penetration. I beleive NASA is working with LEDs. Still seems like their are in their infancy in terms of sophistication and need more time.

There are grow threads on The City that use CFLs or fluoros, and even a LED grow. It works, but with the caveats ive mentioned. Do some searching the LED grow is pretty kool to check out. The problem is the low wattages used leading to smaller yeilds than HPS or MH lighting can produce.

Sunlight Supply manufactures a lighting system that utilizes both a 400w MH and a 400 or 600w HPS bulb under one hood. Its called the Sunsystem 7. My question about this product is does it have the penetration of a 1000w system(ie. does 400w plus 600w equal to a single 1000w bulb). Not sure myself. Once i had the cash to buy my grow equipment i was gonna ask for oppinions on this system, but i havent gotten there yet.

And dont be so quick to discount UV lighting. It may(does) have an indirect beneficial effect on potency.

[tenacity2986]

an 1000 watt will expend more lumens per sq. foot but cover a smaller area

a 400 watt and 600 watt will cover more space, yet less lumens per square foot.


IMHO, option 2 is the way to go. I would rather use 2 400 watt or 2 600 fixtures than a single 1000 watt fixture. I just personally think its more efficient.

[runner's high]

I know there are many different kind of grow lights and that some of them are relatively efficient. But if I'm correct then blue and red fluorescents will be the most efficient grow lights, even more so than white fluoros, CFLs, and LEDs. (LED grow lights might be comparably efficient but they will be much more expensive.)

My information is based on spectral evidence (no pun intended), so it's only theoretical, but I will definitely try a red-blue fluoro grow as soon as I have the opportunity. I don't believe you should have to use 400W of energy to light a few plants, and I don't think you should have to buy expensive mh, hps, or LED lights for a good grow. This should actually work better than all those and it should be more efficient and less costly.

[strenenstaub]

hello.

your graphs are interesting. if was wondering if you had any examples of floro grow lights that would be effective for vegging plants. im fairly new to growing and i was wondering if you could provide me with the specifics so I can go out and compare the models at my local lighting store.

[chimera]

runner you still don't get it, flouros do not have the ability to penetrate. MJ she be a big girl and likes her light all the way to her feet inside and out and the uv thing, I like my buds sugary don't you, trichomes are the plants protection against uv. uv good.

[inthewintertime]

I would stick with MH and HPS as well.

[runner's high]

Originally Posted by chimera

runner you still don't get it, flouros do not have the ability to penetrate

You're right, fluoros don't usually penetrate as much as mh and hps. I didn't mention that because my post was mainly about light wavelength (nm), not light output (lumens). Light "penetration" is a measure of light output/intensity, and since mh and hps are usually more intense than fluoros they are predictably more penetrating and most people argue they are better lights overall. But it doesn't have to be that way. All you need for light penetration is good light output and a good light angle. So just buy more fluoros and use reflectors to focus the light. Considering how cheap and efficient fluoros are, too many people brush them off as inferior to mh and hps. They don't have to be.

Originally Posted by chimera

I like my buds sugary don't you, trichomes are the plants protection against uv. uv good.

Trichomes function mainly as insecticides, but yeah, they also play a role in UV-B absorption. But if you're looking for UV, using a UV-B fluoro would be the most efficient way to get it. It could be a little too powerful--I've never tried them--but they would still be more efficient than using hps or mh.

[Red Eye]

Originally Posted by runner's high

Considering how cheap and efficient fluoros are, too many people brush them off as inferior to mh and hps. They don't have to be.

Absolutely, but very few people setup that many flouros. Youd have to put them all around a plant. You can get expensive tube style formfactors that make setting up a surround light pattern easier, but like i said theyre expensive. CFLs are cheaper but its alot more work. The most efficient/easiet CFL system ive seen is the dual 200w Envirolites with reflector. But its not really cheap at 240, and its a hood so you still have to deal with penetration. Im not sure if they sell them in the US either. I really consider CFLs to be best used as supplemental lighting for an MH or HPS. Especially since you can use a different light spectrum from the main light, to give you a more complete lighting frequency. Because even though the plant prefers more red during flowering and blue during veg, in nature it would receive both.

Originally Posted by runner's high

It could be a little too powerful--I've never tried them--but they would still be more efficient than using hps or mh.

Yea UV-B tubes/CFLs are much more efficient than MH or HPS at delivering UV-B. Heres a good one ive come across http://www.bigappleherp.com/Reptile_Supplies/Product/Reptisun_100_High_Output_UVB_Fluorescent_Light_Ser ies_262180.html
High penetration value with the 10.0 type lights. But you dont leave them on all the time during lights on. Just 2 hours or so, and even then you have to acclimate the plants by starting with less time.

[youngandstupid]

Awesome thread Runner. I tried, half-assedly, to find exactly this info using google and whatnot but I came up with a big 0 in knowledge learned. As far as penetration and it being expensive to buy a flouro set-up that can make up for that fact, I have to disagree. The way I have my grow set up is really simple and I have every part of my girl soaked with light. I just have CFLs hanging on all sides (one side are 2 40" flouros). In total the lights cost probably less that $75.

[Spanishfly]

Excellent post, runner´s high. Good bit of research, nice to see some real science. +rep

[runner's high]

Thanks guys for all the rep. By popular request, here's a graph of mh, hps, and incandescent all plotted against the absorption spectra of chlorophylls a-c (in gray). If it looks a little shabby it's because I edited it in MS Paint.



As you can see, all the lights emit a lot of infrared (heat) radiation. Incandescent lights give off so much heat they are virtually worthless for growing, but you didn't need a graph to tell you that.

The HPS is generally weaker than MH in this graph because I screwed up; the HPS light I picked is of a lower wattage than the MH light. Anyway, you can still tell from the graph that MH is stronger in the blue end of the spectrum and that HPS is stronger in the red end. But notice that both MH and HPS spike at some useless wavelengths: MH spikes in green and HPS spikes in IR, neither of which marijuana wants.

My tentative conclusion: Although MH and HPS are both a little inefficient they each cover most of chlorophylls' absorption spectra so, if you are willing to pay for the watts, they will both be adequate grow lights. This is all that matters to most people, and if it's all that matters to you, go ahead. Just know that a similar effect could be achieved using much less energy with some carefully selected fluoros.

And there are other benefits to fluoros. Here are a few:

(1) They are harder to detect because they emit less heat
(2) They can be put closer to the plants without burning them
(3) They are cheaper than MH and HPS lights

My graphs were based on data from this site. If you want to know more I suggest you check it out. Thanks everyone for your input!

[h4rk4t]

i subscribing to this so i dont forget hah. great info +rep!

[cupcheck]

wow, contrary to what you first might think, this thread is not intended for stoners.

[h4rk4t]

Originally Posted by chimera

runner you still don't get it, flouros do not have the ability to penetrate. MJ she be a big girl and likes her light all the way to her feet inside and out and the uv thing, I like my buds sugary don't you, trichomes are the plants protection against uv. uv good.

But why would you need to penetrate when you can place 5 lights all pretty much just 2 cm away from the buds/leaves....i have a few 30 watt CFL's and you can just let them sit right on the plants heh, i've got a 400watt hps as well...and when you can set the CFLS on a plant and they dont get hot....there is no need at all for much penetration to the feet of her. Check out this dudes grow he's got lights under the plant, the sites....etc and their budding sooooo phat, just find the right set of cfl's or w/e and set em' all over your plant... heh i noticed their an asss load cheaper then my hps and grow just as good if you utilize them correctly.

oh yeah here is the link to the guy i was talkin about http://forum.grasscity.com/grow-jour...oset-grow.html
peace

edit: here is another guy with some prettty dank bud from using this nice ass LED light thing and CFL's http://forum.grasscity.com/grow-jour...seed-grow.html