Lumens Vs Spectrum

Discussion in 'Advanced Marijuana Cultivation' started by RickWhite, Jan 30, 2010.

    Uncle Ben

    Uncle Ben Well-Known Member

    I'm saying that both are full spectrum lamps. I have known people who swear by MH exclusively. IOW, it doesn't matter. Choose the most efficient hood you can and go with a 600W HPS for your best bang for the buck. You're buying light.

    I have been in these age old discussions on light spectrums for years. It comes down to alot of theory and little real world application. You just have to do the experiments.

    Attached is a spectral graph of an Osram Sylvania HPS.

    Attached Files:


    lmn8r Well-Known Member

    Sadly it will likely remain a discussion as long as cannabis remains illegal and socially taboo; as it's tough for universities and research institution to get grants to study it. Until a standardized measuring system for plant growth is created for light bulbs, or peer reviewed scientific analysis is done, it's all going to be he said she said. After all, I doubt there are many PhD's lurking in this forum.


    No one light runs much hotter then any other. It's easy to calculate how much energy as heat each light outputs. The maximum luminous efficacy is 683 lumens/watt; therefore say a 400 watt HPS outputting 50,000 lumens outputs 125 lumens/watt. That calculates to 18% light, 82% heat. 82% of 400 watts is 328 watts of heat.

    A 400 watt Philips CMH bulb for instance outputs 34,800 lumens @ 87 lumens/watt. 12% of it's energy is light so 88% is waste heat, or 352 watts. 352 compared to 328 is negligable. A 24 watt difference = 82 BTU's/hour, or a difference of 1.6 degrees F for a 4x2x8 small closet or 4x4x6 grow tent.
    Hobbes and ANC like this.

    RickWhite Well-Known Member

    Glad to hear someone is doing a trial. I might also bud a plant under the 250W blue MH for comparison.

    From the graphs it is clear that the CMH and the Hortilux Blue emit more light in the ranges used for photosynthesis. Does anyone know what the Y axis ("relative energy") actually means? Because looking at them it seems that the plant can not use most of what the HPS puts out.

    If anyone can attach a spread sheet I would like to bump up the whole spectrum to see what it looks like.

    UB, I hear what you are saying but it just doesn't jive with what I am looking at. I know people grow well with both but these newer bulbs merit some study I think.

    RickWhite Well-Known Member

    Can you attach your spread sheets?

    Also, I'm wondering how you got the figures you did earlier because based on relative energy I found the CMH to put out something like 15 times as much light in the one useable peak and 3-4 times as much in the other over the HPS. The difference in overall light was only about 42% more for the HPS.

    Your figures were far different - 'd like to see how you got there.

    Mcgician Well-Known Member

    No problem. My analysis will be as impartial as I can be. I play no favorites here, although I'd like to think I spent my money wisely. We'll see I guess. The problem I have is that I'd like to narrow down the variables in the equation more than they are and make it a truly scientific analysis, but my grow room isn't quite a real laboratory. What would constitute "evidence" exactly in this case btw? Overall plant growth, including photosynthetic response, or just dried bud weight? I'm willing to guess most people only care about dried bud weight-I know that's what I'm focusing on. And Rick, time to step up to a larger light man. 250 watts is small time, lol. *stick-poke* J/K. :joint:
    Uncle Ben

    Uncle Ben Well-Known Member

    OK. People see what they want to see too.

    Are you saying you're using a "newer" bulb and have empirical evidence that it is superior, or is this discussion just rhetoric based on theory or the latest forum chatter, or what we choose to believe, blind faith? Did the hydro man say it was so?

    RickWhite Well-Known Member

    What I'm saying is that according to all the literature, photosynthesis is driven by light from two points in the color spectrum. 425nm-475nm and 650nm - 700nm. If one were to use a light that emitted only 500nm - 600nm, very little growth would occur.

    According to the published graphs, which is the best I have right now, a CMH compared to an enhanced HPS, emits about 42% less overall light but 15 times more in the blue peak and 2-3 times as much in the red. Or vice versa - i forget.

    Looking at the math:

    The HPS:

    Assume a value of 2 for the red and 142%. 2(1.42)= 2.84

    Assume a corresponding value of 6 for the CMH at 100% 6(1)=6


    So for the one peak which is where photosynthesis occurs, the CMH should put out more than twice as much usable light.

    At the other peak you get 15(.79)=11.85 or almost 12 times as much usable light.

    Of course I am only crunching numbers according to what I see on the graphs of relative energies. I do not know how the term relative energy is being used or exactly what the graphs represent. Nor do I have any actual data. If the graphs show how much blue is emitted in relation to how much yellow, my calculations could be erroneous because this shows only a relation and not actual output.

    In other words, the graphs are shown in relation to a yellow spike. If all data points were squared, the spectrum's might look more similar with the HPS just showing one yellow spike off the chart. This yellow spike might be 1% of total output.

    I'm not sure if the graphs show relation of color to output or color to other colors.
    Uncle Ben

    Uncle Ben Well-Known Member

    That's true but like I said, MH and HPS are full spectrum lights. Maybe your argument is that you think that more output in the 425nm-475nm and 650nm - 700nm range would be beneficial? I finally broke down and went to a HPS enhanced lamp. Really didn't see any difference in plant response. Like I said, you'll just have to let loose of the theory and try it out for yourself.

    good luck,

    lmn8r Well-Known Member

    You can find the spreadsheet there. ^^
    You can find the spreadsheet there. ^^
    You can find the spreadsheet there. ^^
    You can find the spreadsheet there. ^^
    You can find the spreadsheet there. ^^
    You can find the spreadsheet there. ^^

    Neither HPS or MH are "full spectrum" lights. Only black body radiators, such as tungsten incandescent, or.. the sun emit a full spectrum of EM radiation in the visible light wavelengths. Even lights with high CRI such as cermic metal halide, or short arc xenon bulbs have dips and peaks in their spectra, as well as D-line emissions from their root elements.

    I think lighting with the most potential right now are LED lights, because they can be tuned perfectly to the right colors a plant needs. The only problem is they're woefully inefficient compared to sodium vapor light. They'll eventually come down in price but I don't see anything to suggest they'll be ever be able to beat 100 lumens/watt.

    sizzilky Well-Known Member

    <3 u uncle ben u da man
    tea tree

    tea tree Well-Known Member

    veg with t5 or metal halide. flower with hps. ;)
    Uncle Ben

    Uncle Ben Well-Known Member

    I'm sho glad mah plants can't read! Whew doggies.......:hump:

    HomeGrownHairy Well-Known Member

    Data? Prolly, somewhere but, yes, and that's the way it should be. I use a 250 mh for veg and a 400hps for flowering. The higher spectrum K's are better for veg. Far as a 1000w mh, if I were going to use a single HD type bulb throughout the grow, I'd have to grow with an hps, not a mh.

    RickWhite Well-Known Member

    Thanks, but would you tell me what the headings mean? Where did you get these figures?

    RickWhite Well-Known Member

    Well, since these are the ranges in which photosynthesis occurs it makes sense that a lamp that emits more of this light would be more effective than one that emits only a small percentage of its total output in this range. Anything outside these areas is waste.

    sagensour Active Member

    Ive got a 6x7 room vegging out right now(2 week old babies). Im useing 2-1000watt switchables. Running 1-CMH and 1-HPS (eye hortilux) right now(20-4) and will veg for a couple more days till the babies are 11 inches tall. Im building a Scrog screen and installing tonight or tomorrow. I will start a journal with HPS vs CMH tonight. We can compare results. Thanks

    lmn8r Well-Known Member

    CMH only comes in sizes up to 400w. Technically, the Hortilux blue/EYE Quartz Arc HCR bulbs are not classified as CMH, even though they emit a comparable spectrum.

    I assume the two grow areas are separate light-wise? Make sure the gals are of similar size and weight, give them equal watering, equal temps, equal nutes.
    Uncle Ben

    Uncle Ben Well-Known Member

    You're referrring to PAR.

    I understand, you would think that. Doesn't hold true in the real world though, it's like the plant doesn't care as long as both red and blue spectrums are there. I too researched for hundreds of hours for the "perfect lamp" regarding PAR and gave it up when I tried an experiment, which showed me the spectrum this and that is all hooey. Had a acquaintance many years ago who said the same thing. He and his kids tried an experiment using different colored lights on beans and found no difference.


    figtree Active Member

    Rick, I agree.

    I have both spectrums going 2700 and 6500 kelvin and what i notice from my observations is the the plants tend to lean and grow towards the bluer of the light 6500 kelvin. I'm not really up to speed with the exact spectrums that plants use, but the little research ive done gives me the incling to think if your in the exact spectrum the plants need, it would be nothing but beneficial. and if you can get a bulb that only produces those spectrums with enough photons...... it would be explosive growth. I have been watching the led industry (not real close) in hopes i can switch when the prices come down and the technology gets up to speed.

    Now from what i understand, plants are using spectrums that humans dont generally see, or seem very dim to our eyes, just cuz we dont see it doesnt mean its not getting massive photons. ie.... led lighting. gives off less visible light to us but the photons its dumping onto the plant are really what the plants are using.

    Great conversation guys!

    majikmerlin Member

    Amazing read! Thanks all!

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