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Can a light get too efficient

Discussion in 'LED and other Lighting' started by Uncle Reefer, Feb 9, 2018.


    nfhiggs Well-Known Member


    PurpleBuz Well-Known Member

    per the original chart you showed. Its "relative" and not absolute they don't even show an absolute scale. That's the primary reason why the charts look so different.

    absorptance and absorbance are different grammatical forms of the same thing.
    The Daughtry and Walthall paper only talks about absorptance.

    where do you get a definition that absorptance is a fraction of absorbance ???
    the IC graph is absorptance and represents the absorbance by the leaf. It actually confirms the absorptance data that McCree found in his survey and shows us that Cannabis is a pretty typical dicot C3 plant per its absorptance.

    McCree defines their calculations in his paper.

    Calculation of results The following parameters were calculated for each wavelength:
    absorptance = (PMo--PMs)/PM o where PMo = photomultiplier reading without sample; and PM~ = photomulti- plier reading with sample.
    action = kl(C L + Cr~)/I where kl = constant to convert to micromoles/joule; CL = CO/ differential in light; Co = C02 differential in dark (interpolated); and I = irradiance.
    quantum yield = k2(action)/(wavelength × absorptance) where k 2 = constant to convert to moles/Einstein absorbed.
    relative action, relative quantum yield = action, quantum yield normalized to a maximum of 1.00

    so wtf are you talking about ?

    GrowLightResearch Well-Known Member

    But not normalized. Relative does not mean normalized.

    No they each nave their own definition. They probably have their own Wikipedia page.
    Absorptance has many meanings depending on which discipline it is used in.

    You must have missed the post on CI

    Notice the very top line. In general absorptance is a utilized or effective absorbance. Like action.

    Not that I totally agree with writers of that post. I think I understand what they mean. What they say is not all that technically correct.

    Cannabis absorptance part 1.jpg

    When I read the Daughtry and Walthall some time ago my interpretation was it was mostly about reflectance and how to identify illegal cannabis grows from the sky. I did not take the time to figure why they brought McCree into their argument. Reflectance chromaticity is how to identify the color of a cannabis leaf.

    McCree was trying to standardize the term PAR. What wavelengths do plants use and how the energy of photons fits into PAR. So after finding what wavelengths were absorbed then he looked at of the absorbed photons, how many were utilized. Not sure, I think he used CO2 utilization rather than oxygen evolution. Photons are mostly used to oxidize water and secondly to reduce carbon dioxide to other organic molecules.

    The whole point to McCree's absorptance is to see if the energy of the photon had a significant effect on utilization (action). It did not and that is why we use quantum (moles) measurements instead of radiometric (watts) to assess spectral photosynthesis utilization.

    Absorptance is calculated relative to the absorption of photons. It removes the number of photons absorbed at each wavelength from the equation. The charlatan grow light vendors like to use the relative yield to support their spectrum, but it is not a valid use of quantum yield as the percentage of absorbed photons at each wavelength has been eliminated.

    A lot more research has been done on absorbance and action since McCree. McCree still holds up but more is now known. Subsequent studies have refined McCree's findings by including more "actions" their analysis.

    Most of what I have posted in this thread I have fact checked with the well respected text book Plant Physiology and Development. I am an electrical engineer and have no formal training in plant physiology, biochemistry, or molecular biology. I do have a son-in-law (Dr. Thomas Colquhoun) and I regularly ask him questions regarding these sorts of things. He also refers me to textbooks for further information. Thomas also teaches plant biotechnology and is a research professor that heads LED horticulture research at the University of Florida.
    For the past few years I have been building grow light fixtures for his research. I also live in a house owned by him.

    For the past few years my area of interest has been the efficiency of grow lighting and thermal dynamics. I do not like to tell people how smart I am, so instead, I try to sneak into the conversation that my daughter graduated from Harvard Law School at the age of 23. While attending Harvard she also taught freshman Economics there. She met Thomas while getting her degree in Economics at UF.

    I have no commercial interest in grow lighting, it is just a hobby. I know I am a weird mother fucker and I am quite content in that I am not normal. I can't even imagine how awful that must be to be normal. I often say to others if you're trying to be normal, you will never know how amazing you can be. Overcome the notion that you have to be normal. It robs you of the chance to be extraordinary.

    I am pretty fucked up right now so the above may not meet the scrutiny of my RolliTup trolls, I am only trying to help. Sometimes it is better to listen to what I mean than what I say.

    PurpleBuz Well-Known Member

    Yes the terms are used to mean different things but all centered around absorbing. Regardless that's just a distraction. Everybody is talking about light that is absorbed by the leaf ie absorptance. The charts are different because they slammed together two completely different sets of data relative to some whole like 1 or 100%.

    wietefras Well-Known Member

    Well, I indeed agree with SSGrower that's incomprehensible how you can be so wrong all the time.

    You take measurements forming a straight line and conclude "ISL" applies according to those measurements. Even going one step dumber to conclude that because "ISL" applies we should hang our lights higher above the plants to improve "penetration".

    Or now this Chlorophyll nonsense again. McCree's charts show how the whole leaf reacts to light. It shows the plant uses the whole visible spectrum. Chlorophyll charts show how singled out Chlorophyll pigments suspended in water react to light. If we are talking about how the plants as a whole absorb/use the light, who the fuck cares about a single pigment if you have a chart covering the whole? That's why actual growers use McCree's charts. That's my world yes. Reality and actually growing plants.

    Besides, this thread is about efficiency.
    Randomblame likes this.

    GrowLightResearch Well-Known Member

    I understand what you are saying. It is all about absorbed photons. That's correct. But after a photon is absorbed multiple things can happen. One, it can be re-emitted at a higher wavelength, which is called fluorescence. So if it's re-emitted at a different wavelength was it absorbed or not? Some energy is lost in the wavelength conversion. If a photon is absorbed by a carotenoid the carotenoid passes the energy to a Chlorophyll b, which is then passed to a Chlorophyll a, which is then passed to the reaction center. In the process some energy is lost as heat. When a blue photon is absorbed because it has 50% more energy than a red photon the absorbing chlorophyll is in a higher excited state. The chlorophyll must shake off some of the energy to get to the lower excited state of a red photon. So 50% of the blue photon's energy is lost as heat. Sometimes when a chlorophyll is excited by a photon the energy is passed to the reaction center under ideal conditions (e.g. 680nm photon) there is no loss in energy. That ideal condition is the 1 or 100%. It's not a normalization but certainly looks that way.

    Although the photochemical quantum yield under optimum conditions is nearly 100%, the efficiency of the conversion of light into chemical energy is much less. If red
    light of wavelength 680 nm is absorbed, the total energy input is 1760 kJ per mole of oxygen formed. This amount of energy is more than enough to drive the reaction which has a standard-state free-energy change of +467 kJ mol–1
    The efficiency of conversion of light energy at the optimal wavelength into chemical energy is therefore about 27%, which is remark-ably high for an energy conversion system. Most of this stored energy is used for cellular maintenance processes; the amount diverted to the formation of biomass is much less.
    Source Plant Physiology and Development 5th Edition, chapter 7.

    Untitled.jpg Untitled2.jpg Untitled3.jpg

    When the path of a photon is interrupted by an object some of the photon's energy is absorbed and converted to heat. That is pure absorbance. When the photon is absorbed by chlorophyll it's energy is not all converted to heat, it's utilized by the plant, that part not converted to heat is absorptance.

    The way they know this stuff is through experiments like McCree's. There's a lot of stuff the must be measured. That why it looks like a bunch of data being slammed together, because it is. But when someone sorts through the data the result is absorbance. But it's actually very simple. It's just the difference between how much of the photon's energy was utilized by the plant (action) and what was not.

    It's complicated shit. But them scientists are very picky about things like the difference between absorbance and absorptance and it's not easy to understand.

    GrowLightResearch Well-Known Member

    Of course you would. Because you are a dick.

    nonsense? The way you explain it is nonsense and to the ignorant that do not care to take the time to understand but would rather ignore the facts. You are the perfect example of that ignorance. I'm not saying you are stupid you just refuse to take the time to understand and ignore the facts. Textbook ignorance.

    All photosynthetic pigments are in water in the chloroplasts. Singled out??? They are nearly the only pigments used in cannabis leaves 99+ percent..

    Just the two chlorophyll pigments (a & b) involved in photosynthesis that apply to cannabis and other green plants. What other pigments does cannabis use?? Too fuckin' ignorant you are. Amazing how you spout pure bullshit with such conviction.

    Nothing will happen if a photon is not is not first absorbed by chlorophyll or carotenoid pigments. Photons are almost all absorbed by chlorophyll in cannabis. The photon energy absorbed by carotenoids are passed to chlorophyll. It is chlorophyll and only chlorophyll that gets the photon energy to the reaction center of the plant. That is why the absorbance of chlorophyll is very relevant. And that's why yield is relative to absorbance and absorptance.

    Because those two single pigments are what absorb all the light. That is what the charts show including McCree's. McCree's charts have been refined by subsequent studies since 1973. Charlatan grow light vendors use McCree's charts to bamboozle people like you. Getting you to believe that an absorbstance plot shows all spectra are absorbed nearly equally. They are not. Even McCree's charts show absorbance and utilization are much lower (#10 (Castorbean an oil plant) = 58% @ 475nm, and 39% @400nm, 68% mean @ 475nm).

    This is all AFTER (relative to) the absorption primarily by chlorophyll in green plants and secondary carotenoids in leaves with orange pigmentation.

    Last edited: Feb 14, 2018

    Schalalala Active Member

    You have serious problems dude. Or you are trolling. But seeing how much time you spend with your posts, I tend to believe the first...
    The thing is:
    The absorptance spectrum of pigments in a solution is different compared to when the whole fucking plant works together. Is that so hard to believe?

    "Subtle alterations in the molecular architecture of chlorophyll molecules according to the particular protein to which they bind in either light-harvesting or energy-processing centres are responsible for these shifts in absorption peaks, and for a general broadening of absorption spectra (compare lower and upper curves in Figure 1.8). Such effects are further accentuated within intact leaves by accessory pigments and greatly lengthened absorption pathways resulting in about 85% of visible wavelengths being absorbed (Figure 1.10)."

    Source: https://horticulture.ahdb.org.uk/sites/default/files/u3089/Lighting_The-principles.pdf
    Which you and everyone else should really read as it nearly covers everything one need to now about light and plant responses.

    But yeah, an lengthy, overly complicated response from you will follow, where you mix hundred phenomena ups until the result is: Green light is not useful for photosynthesis.

    Attached Files:

    Last edited: Feb 14, 2018
    PurpleBuz likes this.

    mahiluana Well-Known Member

    1L of water need ~ 0,6KW to vaporize

    ...would be interesting if anybody could weigh a (bigger) plant + pot / before and after a light cycle,
    to get some numbers
    Rocket Soul likes this.

    GrowLightResearch Well-Known Member

    You must have missed my post where I said I have issues. The voices in my head have voices. I am far from fuckin' normal.

    That does not change the fact that chlorophyll must first absorb a photon before anything can happen. Absorptance is NOT the same as absorbance.

    From the thread you originally linked to:



    Notice it says: relative RQE ... once absorbed by chlorophyll.

    But NOTHING can happen until a photon is absorbed by chlorophyll. There is no other way to get anything from a photon unless the photon is first absorbed by chlorophyll.

    McCree did not measure "when the whole fucking plant works together". He cut a 25mm² piece of a leaf with a razor blade and mounted it between kitchen sponges for his

    Photosynthesis measurements (Fig. l) A section of leaf approximately 25 mm square was cut with a razor blade and placed, within a few seconds, between two sheets of wet household cellulose sponge. The sandwich of leaf and sponge was then clamped between two sheets of aluminum and screwed into a block in the base of the assimilation chamber.
    Last edited: Feb 14, 2018

    wietefras Well-Known Member

    OK, try to understand how they created those chlorophyll charts. Then come back and apologize.

    Also, I get that you want to bury your stupid remarks in tons of copy pasted material you found somewhere rather than simply admit you were wrong, but nobody cares. What's more, since you without fail misinterpret that extra info it just makes you look more ignorant.

    PurpleBuz Well-Known Member

    You are arguing yourself into a corner ...

    One look at a relative action spectrum for photosynthesis (co2 production) tells us that light of wavelengths through the PAR range and slightly beyond drives photosynthesis. The peak wavelength absorptions for chl a and chl b while significant are only modestly higher than the rest.

    PurpleBuz Well-Known Member

    technical ? lol more like a copy and paste robot scanner that can't connect any of the dots
    wietefras and SSGrower like this.

    wietefras Well-Known Member

    Yet you don't understand the actual difference.

    That part of the leaf still produces the response of ALL THE PIGMENTS in there. So yeah that's in small scale how the whole plant reacts to the light. As opposed to putting some Chlorophyll in a liquid. Which is only relevant for studying that subsystem.

    Everybody, but you, can see the huge difference between McCree and Chlorophyl action charts.

    Also, don't forget that we know you had never heard of McCree a few months ago. There is no use pretending.
    SSGrower likes this.

    GrowLightResearch Well-Known Member

    You're the ignorant one. I explained that.

    Copy and paste? That's called citations something you never do.

    Your typical response, change the subject. Let's get back to your ignorant bullshit regarding the insignificance of chlorophyll.

    You think you understand this stuff better than the authors of the overwhelmingly respected text Plant Physiology and Development?

    I'll make it easy for you. The attached PDF is form Plant Physiology and Development 5th Ed. which is considered the bible of plant physiology.

    Attached Files:


    wietefras Well-Known Member

    No, I'm saying that you are demonstrating that you don't understand that text. Or any other text for that matter.

    Which leads to the incomprehensibly incorrect conclusions you keep making.
    SSGrower likes this.

    GrowLightResearch Well-Known Member

    Yes, that little subsystem where photosynthesis begins. Without chlorophyll there is nothing. Nothing absorbed. Not even any oxygen on Earth. Insignificant?? Your ignorance is astounding.

    You do not know me. Fuck you and the horse you rode in on. Dumbass.

    GrowLightResearch Well-Known Member

    Okay. Please show me what I have said wrong and where in the textbook I got it wrong.

    wietefras Well-Known Member

    It's cute how you desperately try to think of dumb interpretations of what people say. It really only makes you look dumb though.

    How about just sticking to the point. There is a huge difference between McCree and Chlorophyl action spectra. McCree's showing that "green" light is actually used by the plants even though Chlorophyl doesn't use it.

    So which chart is more relevant to us? The one that measures the whole response of the leaf or the chart that measures the response of one pigment?

    Well I do know that a few months ago you lectured the HLG guys for having some "unkown" action or absorbance spectrum on their site. Which according to you "incorrectly" sows significant action on wavelengths between 500 and 650nm. So we took probably about a week trying to explain to you that McCree's charts are actually correct. Yet here we are. Again with the Chlorophyll nonsense. You truly never learn a thing.
    Rocket Soul

    Rocket Soul Well-Known Member

    Depending on plant size a plant can drink up to a gallon or more=+3.5 kg

    0.6kw per litre: are those numbers for boiling water? Doesnt seem to add up with real life examples: 20 plant SOG on 1 1x1m tray drinks aprox 20 litres (12kw of vaporation) a day under a 600 hps which will produce 3.6 KW of light and infrared (.6x12x0.5: assuming 35% light + 15 % infra red heat). But maybe i missunderstand you.
    I think maybe the plants know how to cheat ;)
    SSGrower likes this.

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