Ulbricht sphere PAR test (PPF) of several popular 1000W lamps

[joe fresh]

well im hoping you can test out the bulb and ballast as they are usually full of hype promoting, just wondering if they stand up to what they claim or if its inferior to what they claim

 

[whazzup]

as soon as we have it we will. promised.

 

[shirami]

whazzup,
Do you have any opinion as to which 1000w bulb/ballast combo may be best that could also be used in a vertical position?

I was thinking perhaps Phillips Aggro-Lite XT with a MicroMole or Solis-tek ballast?

 

[onegreenday]

Is this the Gavita SE bulb tested in your chart?
Thanks.

(from Gavita website)

Gavita Enhanced HPS 1000 W

Brand: Gavita
Type: Enhanced spectrum HPS lamp
Power: 1000 Watt
Lumens: 130.000
Growlight (µMol): 1750
Voltage: 230

to put it in perspective: The percentage shows how much more light this lamp produces compared to the next lamp in the line-up.

 

[knna]

That's a good question. I never understood PAR watts, but let me try to break it down for you. As far as I know Sunmaster uses PAR Watts. As they are the only or one of the few who use it it is hard to compare to anything else.

So though they acknowledge that ppf and ppfd are good ways of measuring light they focus on how much enery is converted by the lamp in the 400-700nm PAR spectrum. If I understand it correctly they measure the energy of the photons between 400 and 700 nm, but express that in energy.

The claimed highest PAR Watts unfortunately doesn't seem to correlate with high growlight output. Don't ask me why, I never calculate with PAR Watts.
12-17-2011 08:01 PM

Just to help clarifying this topic, both PAR Watts and PPF (Photosynthetic Photon Flux) are radiometric measurements of light output.

But plants uses photons, not watts, so the accurate and meaningful figure which most closely relates to photosynthetic outcome is PPF, in micromols of photons per second.

1 PAR watt of blue photons carries about 3.5 µmols while a red ones holds more than 5 µmols. More than 40% more photons for same PAR output.

It happens because energy of a photon is inversely proportional to its wavelength, so between 650 red photons and 450nm blue ones, there is 650/450=1.44, 44% more red photons than blue ones, or said inversely, there is 450/650=0.69, 31% less blue photons than red ones. And photosynthetic effect is related to number of photons, the excess energy is dissipated as heat into the leaves.

In order to avoid such confusion and use the figure more useful, as the most correlated with growth induced, botanist uses PPF and not PAR Watts, aswell as most manufacturers of horticultural bulbs.

Anyway, most HPS bulbs emits a very similar amount of photons on each PAR W, as their spectrum are very similar, ranging from 4.6 to 4.75 µmol/s on most cases (very blue enhanced bulbs can go a little lower, 4.51 for the Hortilux). Horticultural HPS usually are close to 4.65 µmol/s (4.66 on average for the Phillips GP).

So when having a PAR Watt figure from a HPS bulb, you can get a figure in µmol/s with small error margin, just multiply it by 4.65 and figure obtained won't by off by more of 1.5% of total. For example, say a HPS bulb emits 260 PAR W, then its PPF is 1209+-18 micromols of photons per second.

 

[Shafto]

Just to help clarifying this topic, both PAR Watts and PPF (Photosynthetic Photon Flux) are radiometric measurements of light output.

But plants uses photons, not watts, so the accurate and meaningful figure which most closely relates to photosynthetic outcome is PPF, in micromols of photons per second.

1 PAR watt of blue photons carries about 3.5 µmols while a red ones holds more than 5 µmols. More than 40% more photons for same PAR output.

It happens because energy of a photon is inversely proportional to its wavelength, so between 650 red photons and 450nm blue ones, there is 650/450=1.44, 44% more red photons than blue ones, or said inversely, there is 450/650=0.69, 31% less blue photons than red ones. And photosynthetic effect is related to number of photons, the excess energy is dissipated as heat into the leaves.

In order to avoid such confusion and use the figure more useful, as the most correlated with growth induced, botanist uses PPF and not PAR Watts, aswell as most manufacturers of horticultural bulbs.

Anyway, most HPS bulbs emits a very similar amount of photons on each PAR W, as their spectrum are very similar, ranging from 4.6 to 4.75 µmol/s on most cases (very blue enhanced bulbs can go a little lower, 4.51 for the Hortilux). Horticultural HPS usually are close to 4.65 µmol/s (4.66 on average for the Phillips GP).

So when having a PAR Watt figure from a HPS bulb, you can get a figure in µmol/s with small error margin, just multiply it by 4.65 and figure obtained won't by off by more of 1.5% of total. For example, say a HPS bulb emits 260 PAR W, then its PPF is 1209+-18 micromols of photons per second.

Wait a minute, now I'm more confused knna.

The energy of a photon is inversely proportional to it's wavelength yes. This means that short wavelength (450nm blue) photon is more powerful than a long wavelength (660nm) red photon. Blue light carries more energy, not the other way around.

Par Watts and PPF are the same thing stated in a different way. It's radiometric power in the range from 400-700nm, it's that simple. Par Watts and PPF are faulty mechanisms for measuring how good a light source will be for photosynthesis, because they weigh all photons evenly between 400-700nm, when plants don't see photons evenly, and neither do we.

That's why we have "lumens" which is a measurement adjusted to the sensitivity of our human eyes. "Lumens" gives green photons much more weight, because we're so much more sensitive to green than we are to red or blue.

YPF PPF is the true measurement of how useful a light source will be for photosynthesis, and unfortunately not used very often, or even known about outside of the professional lighting world. YPF PPF weighs photons in the range of 360-760nm according to photosynthetic response by the plant, just like lumens does for our eyes. It turns it into a useful meaning.

 

[whazzup]

Yes I think you are confused . I totally agree with knna. PAR Watts and PPF ar different. PPF does not take into account that a blue photon has a more energy, because photosynthesis is not related to the amount of energy, but the photon count. It's the photon hits that excite. Excess energy is mostly dissipated as heat.

Plants see a lot more colors than we do and that is why PAR is defined from 400-700 nm. You can weigh the ppf curve according to the sensitivity curve of the plant (the 70's McCree curve which by the way is updated at the moment) or you can do a flat 400-700 measurement. In the first case more red light would positively influence the result (plants respond more or more efficient to red light), but you would not be counting/representing all photons emitted by a source any more. Micromoles are only an indication of photosynthetic potential. For light you always need to take into account how these photons are divided throught the lamps spectrum. I can assure you 1000 micromoles pure yellow light has a different effect on a plant that 1000 micromoles full spectrum light. They could have the same PAR Watts though.

For comparable sources of light (HPS in this case) PPF says a lot about the photon output of a lamp. In practice we see that increase of ppfd influences yield in a, to a limit of course, linear way. I have (printed) scientific studies here that evaluate the validity of using ppf and ppfd in horticulture. Most universities world wide (not only in Europe) and all horticultural research uses PPF/PPFD. All horticultural suppliers work with PPF/PPFD. Now I am not saying that because everyone uses it and has agreed to this standard we all should, but I do think there is a pretty good case for PPF/PPFD. But again, the other factor in light is the spectrum.

There are companies that say PAR is incorrect because also UVA has a considerable effect, as does far red. All valid points maybe, but there is a lot of research that needs to be done to confirm that. It is not until very recent that we are able to make lighting efficient in better spectra. There is still a lot more research to be done. Gavita was one of the first companies to switch to PPF/PPFD and we will do so as long as the industry regards it as best way to measure the output of a lamp in the PAR spectrum. When something better comes along we will be the first to hop on board.

 

[whazzup]

whazzup,
Do you have any opinion as to which 1000w bulb/ballast combo may be best that could also be used in a vertical position?

I was thinking perhaps Phillips Aggro-Lite XT with a MicroMole or Solis-tek ballast?

The Philips Agrolite XT is a good lamp and it can be used vertically. I am not an expert in vertical grows, but I think a combination with the MicroMole would be a good one (remember the agrolite was never built for electronic ballasts though!). I have no experience with the Solis-tek ballasts.

Some extra advise for the MicroMole (and any other similar 120-240 fan-less ballast): it is a 120-240V ballast, but it runs coolest and most efficient on 240V. If you have it, use it. Always mount the ballast vertically, that will cool it much better and will prolong the life of your electronics.

 

[whazzup]

Is this the Gavita SE bulb tested in your chart?
Thanks.

(from Gavita website)

Gavita Enhanced HPS 1000 W

Brand: Gavita
Type: Enhanced spectrum HPS lamp
Power: 1000 Watt
Lumens: 130.000
Growlight (µMol): 1750
Voltage: 230

That is a lamp that can only be used in European 1000W ballasts. They work on a lower voltage and are not that efficient in higher wattage, that's why in Horticulture we use 400V equipment and high voltage lamps.

What was tested is the Gavita Enhanced 1000W E39 US lamp we are introducing next month after 1,5 years of trials. We postponed introduction 3 times because we wanted to improve certain elements, with this result.

We actually decided to stop selling 230V 1000W EU lamps as they are no match to the high voltage lamps.

 

[knna]

Wait a minute, now I'm more confused knna.

The energy of a photon is inversely proportional to it's wavelength yes. This means that short wavelength (450nm blue) photon is more powerful than a long wavelength (660nm) red photon. Blue light carries more energy, not the other way around.

Exactly, blue photons are more energetic, that's why there is less for a given energy (as 1 PAR Watt). If you divide a total on smaller units, there is more units than if you divide it on larger parts

Par Watts and PPF are the same thing stated in a different way. It's radiometric power in the range from 400-700nm, it's that simple. Par Watts and PPF are faulty mechanisms for measuring how good a light source will be for photosynthesis, because they weigh all photons evenly between 400-700nm, when plants don't see photons evenly, and neither do we.

PAR Watts is faulty because plants dont use watts, but photons. It not take into account the SPD (Spectral Power Distribution) of the light source, just its total power.

While photons number is directly correlated with photosynthesis. Plants use photons for driving photosynthesis, a minimum of 8 are required to dissociate a molecule of water, irrespective of the energy they are carrying. In the practice, plant requires a higher number of photons, because the process is not perfect and plants have photoprotective mechanisms which consumes photons. The best they can do is 1 carbon fixed each 10.5 photons on average (670nm photons, perfect conditions), usually they need from 12 to 14 photons per C fixed.

So as amount of photosynthesis is directly related to the number of photons absorbed by the plant, knowing the output in photons of a light source is by far the most meaningful figure you can get for horticultural applications.

That's why we have "lumens" which is a measurement adjusted to the sensitivity of our human eyes. "Lumens" gives green photons much more weight, because we're so much more sensitive to green than we are to red or blue.

YPF PPF is the true measurement of how useful a light source will be for photosynthesis, and unfortunately not used very often, or even known about outside of the professional lighting world. YPF PPF weighs photons in the range of 360-760nm according to photosynthetic response by the plant, just like lumens does for our eyes. It turns it into a useful meaning.

The problem is although human sensibility is well defined on photopic conditions (color vision with decent light intensity), photosynthetic response is not so well defined at all.

Actual photosynthetic response depends of the plant specie you consider. Different leaves morphologies has different absorption/reflection depending of the wavelength. Shape is similar for all, but relative difference between species is noticeable.

And once absorbed, all photon into PAR range has a very similar ability to drive photosynthesis. Photosynthetic quantum yield is pretty flat.

But not only that, but photosynthetic response depends of the light level and other factors as CO2 available and temperature, so you cant convert to YPF on a way valid for all conditions. Indeed, wavelength with the highest efficacy on lowlight conditions often has the lower efficacy at high light conditions.

I developed a sheet to calculate photosynthetic efficacy based on the efficacy of photons driving photosynthesis as a way to check how good is a spectrum for plants growing, but the only way of doing it is doing some assumptions that often are not true on the real world.

Best photosynthetic response curves are those of Inada and McCree. The first studied the response to incident PAR Watts of each wavelength, the second to absorbed photons. Their curves are averages of several species, and performed on light levels not limited by CO2 availability. You can't expect same response when you grow plants at way higher light levels (CO2 limited) as we always do when growing our magic plant. And in fact, it is not the same.

Not only that, those photosynthetic response curves are calculated for isolated wavebands (2nm wide on both cases), without including synergistic effects between wavebands which happen when using them together.

So although calculating PYF and other photosynthetic indexes is very useful, you cant say they are more meaningful or best correlated with photosynthesis than the total emission in photons. For sure that is true that different spectrums has different efficacies, but for calculating it on a meaningful way you need to consider specie being grown, light and CO2 level used and synergies between wavebands used.

For general horticultural info, output in micromols of photons is the best you can get.

 

[whazzup]

lol and we didn't even orchestrate that

Thanks knna

 

[Shafto]

I think some of the confusion was lost in translation. knna, I thought you were saying that red photons contained 44% more energy than blue photons.

So the PAR Watts take into account the extra energy of shorter wavelength light, because it carries more energy, whereas PPF just counts the photons between 400-700nm, weighing them all equally. I should have realized that, I've never worked with PAR Watts before.

While a green photon, once absorbed, may be just as useful as a red or blue photon, the plant has a much harder time absorbing the green photon to put it to use, therefore the green photon should not have the same weight as a red or blue photon, and this is where PPF is flawed.

Completely true that many outside factors will influence the conversion to YPF PPF, but using some constant figures to make a general conversion would still be more useful than PPF.

Using a 100W 555nm lamp will have the same PPF as an 84W 660nm lamp. A plant will however, grow much better under the 660nm lamp.

Applying a generic YPF conversion will be much more useful in defining how useful a light source will be for photosynthesis.

 

[shirami]

That is a lamp that can only be used in European 1000W ballasts. They work on a lower voltage and are not that efficient in higher wattage, that's why in Horticulture we use 400V equipment and high voltage lamps.

What was tested is the Gavita Enhanced 1000W E39 US lamp we are introducing next month after 1,5 years of trials. We postponed introduction 3 times because we wanted to improve certain elements, with this result.

We actually decided to stop selling 230V 1000W EU lamps as they are no match to the high voltage lamps.

Is this lamp designed for electronic ballasts?

 

[whazzup]

@shafto: Please read my remarks: with ANY ppf measurement you have to take into account the spectrum. Comparing PPF is a good general tool.

Using a 100W 555nm lamp will have the same PPF as an 84W 660nm lamp. A plant will however, grow much better under the 660nm lamp

.
I do not necessarily agree with that. They will both perform really bad because of narrow spectrum, specifically in a generative stage. You can easily do the test with LEDs. Also you need to take into account the efficacy of the lamp. 100W input doesn't mean 100 PAR Watt output.

I don't have all the answers, there is still much ongoing scientific research. Until there are more reliable sources we stick with PPF: that is the only way to measure full photon flux from lamps.

@Shirami: We have this lamp for the US as Enhanced (standard magnetic and electronic ballasts) and Pro (high frequency high voltage ballasts such as our Pro-line ballasts). They have been approved for our DigiStar ballasts, we will test them for other electronic ballasts as well to see if there is any acoustic resonance, but yes, these have been developed to withstand high frequency energy in the construction.

Every lamp has a different resonance frequency, every E-ballast has a different frequency output. Those need to be matched.

 

[Shafto]

@shafto: Please read my remarks: with ANY ppf measurement you have to take into account the spectrum. Comparing PPF is a good general tool.


I do not necessarily agree with that. They will both perform really bad because of narrow spectrum, specifically in a generative stage. You can easily do the test with LEDs. Also you need to take into account the efficacy of the lamp. 100W input doesn't mean 100 PAR Watt output.

I don't have all the answers, there is still much ongoing scientific research. Until there are more reliable sources we stick with PPF: that is the only way to measure full photon flux from lamps.

I did read your remarks, though I'm not sure what you mean with this "ANY ppf measurement you have to take into account the spectrum." The spectrum is stated, it's 400-700nm, that's what PPF is. Total photonic flux from 400-700nm.

My example of green vs. red light would hold true, though obviously the plant would do poor under only red light, the red light is much more useful to the plant than green light, which you can easily understand by looking at any graph relating chlorophyll A or B response to light. Also, we're not talking about lamp driver efficiency, so why would you bring up 100W intput isn't going to be 100W output of light? Of course not.. but that's not what we're talking about here. Call it an imaginary perfect lamp if you want, or imagine they have the exact same efficiency and efficacy, it really doesn't matter, it's still a sound comparison proving why PPF is flawed.

PPF says that a green photon is as useful to a plant as a red or blue photon. Whazzup, would you agree that green light works just as well for growing plants as red or blue?

People use green when lights are off for a reason, that plants don't see it nearly as well as red or blue (and we see green very well). Ever wonder why a plant's leaves are generally green? That would be because they mostly reflect green light, while absorbing red and blue.

Green photons are not as effective as red or blue photons for plant growth. PPF does not account for this.

YPF PPF takes into account the response the plant has to different wavelength photons, it's a better measurement, there's no argument here.

 

[knna]

Shafto, please read again my arguments about why YPF and other indexes not necessarily are more informative, but in some circumstances they can be misleading. While PPF is a very objective figure of a lamp's output and the best correlated with photosynthetic response.

How good that PPF actually induces photosynthesis then depend of how you use it, and not so much of the lamp itself. Reflectors, grow design, CO2 level, plant specie, light density....are factors that will affect the performance of any given light.

Addressing your example, you could think looking at chlorophylls absorbency graphs or photosynthetic response curves than for same photon count of 555nm or 670nm photons, the latter performs better. It is true on many conditions, but not on all conditions. Not only that, the difference in performance between one and the other varies as conditions varies:

Upper layer of leaf absorb most red photons reaching it. But once chlorophylls on the upper layer are saturated of red photons, ability of the leaf to use more red photons is strongly minimized. Carbon fixed on the inner part of the leaf can account higher than C fixed on upper layer, more as thicker the leaf you consider (plant specie and light acclimatization has a role on this). Green light penetrates deeper in the leaf and drive photosynthesis on that part of the leaf. Under very high light irradiance and specially, when there is a background red light, green light can drive more C fixation than red light.

But still when red light outperform green light efficacy, how do you measure it in order to express it quantitatively on a index as YPF? For what plant? What CO2 level? What average irradiance?

Those indexes are useful, but you need to understand their limitations. They work for isolated wavebands or broad 400-700nm spectrum at low light levels. But when things varies, they are anything but accurate.

Im afraid such indexes might be used for dishonest sellers in order to hide the actual performance of their lamps (emission in photons per Watt) on cryptic indexes which only a few understand their meaning.

So such indexes are very useful, but when you understand their limitations. And they are more referred to how you use the lamp than to the lamp itself. So for lamp's specs, Im all with the use of PPF as the most objective measurement of its performance.

 

[Shafto]

But still when red light outperform green light efficacy, how do you measure it in order to express it quantitatively on a index as YPF? For what plant? What CO2 level? What average irradiance?

Please read what I wrote earlier.

From McCree "Photosynthetic spectral efficiency is remarkably similar among species"

Use average atmospheric CO2, say 400ppm.

Not very difficult to come up with a generic measurement that we can all use.

Dishonest sellers calculating their own YPF PPF could use figures to make their product look better, and that wouldn't be good, but what I'm talking about is a general way to calculate YPF from PPF with known constants, just like lumens. Light sources could be then compared to each other more accurately for how well they induce photosynthesis. There should be an industry standard way to measure YPF PPF.

We don't even need to worry about CO2, We're not measuring that, make it some agreed upon constant. Just give photons more easily absorbed more weight. Exactly like what is already done for lumens and our eyes. We all have different eyes that respond differently to light depending on the person and light level (just like plants), but we can still find the general medium and make an index that works well, see here:

http://hyperphysics.phy-astr.gsu.edu/Hbase/vision/efficacy.html

Horticultural HID manufacturers will cling onto PPF for dear life, as it will make their light sources look good compared to emerging LED products, however the LED products will have their PPF in wavelengths much more easily absorbed by plants, and will therefore have a much higher YPF PPF than their HID counterparts. PPF may work primitively for HID-HID comparison, but it's not a good tool to compare different light sources, because it doesn't take into account how the plant reacts to different wavelength photons.

A green photon is not as useful to a plant as a red photon or a blue photon, and therefore giving them the same "score" is not appropriate.


By the way knna and Whazzup, this is a most excellent conversation! Thanks fellas.

 

[whazzup]

I did read your remarks, though I'm not sure what you mean with this "ANY ppf measurement you have to take into account the spectrum." The spectrum is stated, it's 400-700nm, that's what PPF is. Total photonic flux from 400-700nm.

What I meant to say is that I do agree with you that 100 micromoles of one color is not the same as 100 micromoles of a for example full continuous spectrum. If you compare lamps you can not always just compare PPF, there are other factors that define the quality of a lamp, specifically spectrum. You can not compare 300 micromoles 640 nm with 300 micromoles full spectrum light for example for effect on the plant. But that is not what we are measuring now.

If you glance at the spectrum of HPS you will not see much difference between the lamps. If you look more carefully and with better detail you do see many little differences. If you would see 10 different HPS lamps lit next to each other you would see slight differences: some more yellow/orange, some more light yellow. Anyways, how we perceive it. So there is a difference indeed. But in general they are comparable because they more or less work in exact the same spectrum. So that's why I feel it is allowed to compare these lamps using micromoles. For the effectiveness of the lamp, with same purposes, we can compare.

My example of green vs. red light would hold true, though obviously the plant would do poor under only red light, the red light is much more useful to the plant than green light, which you can easily understand by looking at any graph relating chlorophyll A or B response to light. Also, we're not talking about lamp driver efficiency, so why would you bring up 100W intput isn't going to be 100W output of light? Of course not.. but that's not what we're talking about here. Call it an imaginary perfect lamp if you want, or imagine they have the exact same efficiency and efficacy, it really doesn't matter, it's still a sound comparison proving why PPF is flawed.

If you just look at the chlorophyll response then only red an blue LEDs would be the perfect solution. I think we all know that that theory did not completely work out as expected.

Let me explain why the lamp input power imho is important:

We defined the output per Watt lamp power, not system power. We use a custom electronic ballast which we can fine tune to meet the lamp manufacturers specification for lamp input within 0,5%. We measure that balllast output to the lamp with a high frequency power analyzer, so we know exactly what is going to the lamp and tune to that. So all the lamps get the right power. Another way of doing it is to use a magnetic ballast and a Variac.

PPF says that a green photon is as useful to a plant as a red or blue photon. Whazzup, would you agree that green light works just as well for growing plants as red or blue?

Maybe not as good but it has a function. Take a look in the sunlight spectrum: there is a lot of green light in it and less red. That might explain why a plant uses it differently. I am a firm believer in full spectrum btw. HERE is an interesting read.

People use green when lights are off for a reason, that plants don't see it nearly as well as red or blue (and we see green very well). Ever wonder why a plant's leaves are generally green? That would be because they mostly reflect green light, while absorbing red and blue.

Green photons are not as effective as red or blue photons for plant growth. PPF does not account for this.

Some wavelengths have important signal functions. The fact that green light does not disturb your flowering cycles does not mean it is not effective. According to the McCree curve green is not ineffective. The reason why plants might not use it as they do with other light is exactly what knna explained. And there are plants with much different response spectrums and light recipes.

YPF PPF takes into account the response the plant has to different wavelength photons, it's a better measurement, there's no argument here.

Yes but a good measurement of what? And how would a lot of red light influence the score compared to ppf?

For lamp output you have to take all photons within PAR into account. That is what you are trying to compare: the efficacy of a lamp. If I put in 1000W as specified, how many photons within PAR doe ik get from them? If they are useful and within the PAR spectrum is a matter of reading the spectrum. Spectral quality is hard to grasp in a figure.

 

[knna]

I dont think it is fair to use a index which depends of the actual use of the lamp. If a lamp manufacturers want to offer YPF or other index along with absolute PAR emission in photons, its perfect. But first and essential, how many micromols of photons emits a lamp.

And actually, Ive checked that output in photons correlates the best with photosynthetic inducing potential of the lamp, irrespective of the type of spectrum considered, if you look for a wide range of growing conditions.

Yes, typical LED spectrums works great at low light levels, typical of nursery or veg stage for MJ. Its spectral efficacy (C fixed/mol photons) can double that of an HPS spectrum in that conditions. But on the other hand, as you increases the light density in the grow area, that difference goes narrowing and may become negative at high irradiance (HPS higher spectral efficacy).

For the moment LED grows have proven to be able to get high g/W always you are fine with low g/sq ft. If you want to match the yield of a 1000W HPS on 15 sq ft, probably you would need to use more photons of a typical LED spectrum to yield the same.

At high irradiance, assuming all photons are equal performing photosynthesis is actually closer to reality than anything else. When NASA started experiments on plant growing for the future mission to Mars, they were very concerned because, based on Inada and McCree, MH have higher spectral efficacy than HPSs. It was a concern because while energy budget in space is limited, initial cargo is more limited yet, and MH have shorter lifetimes and obliges to carry more lamps. Later they observed than when using lamps on light saturating conditions, actually HPS outperformed MH.

Extrapolating indexes calculated under some strict assumptions to general conditions is mislaading and often lead to wrong conclusions.

On the other hand, if you have the PPF of a lamp and its SPD, you can make good estimations of performance for given conditions (plant specie, light density, CO2) and select the best option.

But Im been saying for years that the most important thing about a growing lamp is their photon output because spectral efficacy of most lamps is similar, often not varying more than 25%. If you use a lamp emitting 25% less photons but having a 25% improvement on spectral efficacy, actually you end yielding less (because 0.75*1.25=0.94<1).

And based on YPF and other indexes, spectral efficacies are below 15% for all growing lamps. While in the practice, you can get up to double spectral efficacy, but it needs a perfectly tuned spectrum for the growing characteristics (plant specie, light density, CO2...).

Advantages of LED lighting are about the reduced light losses (no reflectors), better light distribution and best efficiency (but this is something which is being achieved right now, not years ago) and the possibility of tune the spectrum. But the spectrum is just one of the advantages, and not the main IMHO. And in some sense, it can be a disadvantage, because some LED colors have low efficiencies.

 

[knna]

lol! Whazzup, lately we are synchronized