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PPFD Grow Light Comparision

What do you think?

  1. PAR is not about energy, it is a wavelength range of 400-700 nm
  2. you are doing exactly what you say not to: skew data by not measuring ALL the light from the fixture, but just on a limited grid with an uneven sample, favoring straight under the lamp. You can not integrate all light from a medium to medium wide fixture on such a surface. Any deep fixture will show up favorable against medium of medium wide fixtures.
  3. A spectrometer actually DOES measure intensity. You should watch the scale more accurately. A spectral diagram however is always given with the strongest color at full scale. As a spectral reading as such does not say anything about the output of the fixture, the scale is normalized to 100%
  4. You don’t have to couple a ppfd meter to a calibrated spectrometer to measure PPFD. If you use an appropriate meter it will integrate all the measured data and recalculate it based on the planck constant and the wavelength into ppfd. You can select any range of the wavelength in your analysis software to get a PPFD value from that range.
  5. The Lighting Passport is a spectrometer that actually makes that conversion.
  6. The actual wattage of a 1000W Gavita is not 1200W
  7. A CMH doesn’t use 315 W, that is only the lamp.
  8. The power used is not an indication of the efficiency, as you imply.
  9. Just take a look at the throw of the fixtures. Most of those (deep) LED fixtures hardly cover the area, while the Gavita even lights the wall!! Most of the Gavita light is going to the outer side, not downward. Scroll to 7.30 and see for yourself. Same with the Spyder. Guess which fixture has a deep throw huh?
  10. There is not “much needed light” straight below the light. For a uniform and well penetrating light you need overlapping light.
  11. “More importantly: These are white LEDs. And many of these photons will be reflected by the plant.” Come on, green light in high intensity white light is actually considered to be more effective than blue and red. red and blue alone is not the key to healthy growlight. Those graphs are nonsense at 9.15. According to these graphs even McCree was wrong. We are talking photosynthesis here. Look at the sun and learn. “this portion of light is largely ignored by the plants”(9.50): nope. Incorrect information. Doesn’t make any difference for photosynthesis. As he earlier explained: it is a photon count response.
  12. 9:56: “recreating the inefficiency of HID grow lights” The sun is recreating the inefficiency of HID grow lights.
  13. You know you are being conned when an LED manufacturer says they produce twice the amount of light with a much lower wattage (in this case, 630W). That is practically and physically impossible. The theoretical maximum of energy conversion to light, when 100% of all energy would be converted, is, depending on the spectrum about 4-4.5 umol per W. The VERY BEST LEDs at the moment can do (at reduced power) 3 umol/W. And they are very pricy.
  14. 10.48: “Our goal here is to do a fair side by side comparison” :smiley: failed, sorry.
  15. 11.10 - “have an unmatched intensity. This is thanks to our simple but effective secondary optical lenses.” In plain english: we concentrate all the light straight under the lamp, like a torch.

What does this mean? It means that you do not know a lot about measuring light or try to willfully mislead your customers. What you SHOULD have been talking about is ppf: the total output of a fixture.

It’s really easy to focus a flashlight on a small surface and say “see, this little light gives me more intensity” Even an iPhone can do that.

What is the difference between ppf and ppfd?

How do you measure fixture output? With a PhotoGoniometer.

What is the fixture efficiency? PPF of the fixture / power used by the system.


2 posts were merged into an existing topic: Lighting 101

2 posts were split to a new topic: Lighting 101

To complete this topic about Kind LED communication, here is the result of a previous video, with quite a bit of fear mongering and incorrect data as far as I am concerned. There is a bit of a pattern there so I would like to include this in this discussion. I would like to see Kind LED’s response to this. Of course you can disagree about things, but here is how I see it:

Round 1
Yes, the Gavita fixture is 400W higher in power. In a closed grow you need 400W more cooling. However, you get much more output as well. Kind LED does not publish its fixture efficiency, as professional lighting companies do. Fluence, Illumitex, Valoya etc etc all do. You may be or may be not impressed by them, but at least they publish them. Here is the efficiency of LEDs according to the manufacturer’s websites:

Clearly Fluence is leading here at only three time the cost compared to HPS.

Round 2
More power consumption is not bad at all. I doubt if Kind LED will come to 1.9 umol per W output, that is what you look at when you look at power: is it used efficient, and what it brings you as output. Did anyone ever see the fixture ppf of Kind LED? A 2000W LED lamp uses twice the power of a 1000W lamp. So?

Round 3
Yes, the Gavita lamp has a much shorter life span. However, over time by changing the lamp you go back to 100% output. LEDs do fall back in output too. So we doubt if you would still be using it in 10 years. you can’t change the LEDs. But in life span this definitely goes to the LED. But it comes at a price: the 630W lamp costs $1,895.00. For that you can buy 4 Gavita 1000W fixtures. Or you can change a lot of lamps.

Round 4
Yes, lamps contain mercury so you should recycle them. You would not be very environmental friendly if you would not. So no issue. If you install your fixtures safely there is no fire hazard. Fear mongering.

Round 5
Better quality yield. Well, I’d like to see that, because I don’t think they did very well with the 1000W DE, getting less than a gram per Watt. But, a better spectrum could give a better quality. So in the one to one the Gavita easily wins on yield if used correctly, but that is not the metric you need. You are comparing 1000 against 630W. The next metric is probably a bit more important

Round 6
Anyone who grows less than a gram per Watt under a DE HPS should be ashamed. I bet they used it in the same type of room than the 630, or had no walls at all. I’d like to see this setup because this is ridiculous.

Now under a lower ppfd you should be able to get a much better grams per Watt. If you want to see how effective each light is expect that you need almost twice the size room to get the same average ppfd from the 1000W HPS average. Of course you would use a SR reflector for single fixture use, as the DE is meant for overlapping plans. But even so, a much better result should have been obtained.

Then there are of course the averages and min/max data that can not be compared because not all light was integrated. But based on only that data here is another round:

Round 7 - uniformity
Even with the standard reflector the min/avg uniformity is much higher: 59% against 35% for the Kind LED LED fixture, that should actually have an advantage on this small footprint because of the deeper beam. Let alone the min/max uniformity. In a G1 tent with the SR reflector uniformity under a 1000W lamp is over 90% (!).

Round 8
We already touched this. A 630W Kind Led fixture is 4x as expensive as a 1000W HPS. So let’s assume that they are at least as efficient as we are. You know what? I give them to make the comparison a bit skewed in their favor 10% advantage in efficiency (don’t believe it but still), I’m kind ;)). Let’s say you want to light 200 square meters with a ppfd of 1000 umol s-1 m-2. You need about 100 DE fixtures for that. Assuming kind LED is 10% more efficient that’s about 152 fixtures. Let’s use the GrowersHouse prices for the reference comparison:

100 X Pro 1000e DE (450) = 45.000
152 x K5 XL1000 (1.695) = 257.640

Again, this is assuming that they produce 10% more light. Even with 100% more light efficiency than ours (which is physically impossible) it would still 3 times as expensive. You can buy a lot of lamps (or other LEDs) for that… (@Fluence you are welcome ;)) .

I’ll make some free promotion for Kind LED here, so you can judge yourself.

So I welcome your take on this, and especially Kind LED’s of course.


@Theo you list the Gavita Pro 1000e at $450 and our VYPRx PLUS at $810… that’s not even 2x, let alone 3x. Please show your math, sir. -TW


Reminder to stay polite and not make any personal attacks.


“Our goal here is to do a fair side-by-side comparison…” Well, you failed.

Simply because you ignored the manufacturer’s recommendations and fixed the mounting height at 36” and 48”. In what “fair” study do you blatantly ignore a manufacturer’s recommendation? Most likely one that benefits your product… oh, interesting, you recommend 24” – 48”. Fancy that.

So, why are we taking the time to comment specifically about the flaw of fixing your mounting height. Simple – because (as you know) mounting height plays a MAJOR role in the intensity & uniformity of PPFD. Most fixtures have a poor design (and/or emit too much radiant heat – here’s looking at you, HPS :wink:) to mount close to the canopy.

SPYDR is purposefully designed to be mounted 6” from the plant canopy (or in the case of this video, 6” from your testing plane). Specifically because we designed SPYDR for vertical farming applications (like this one). When deployed correctly (i.e. per our recommendation), the SPYDRx PLUS has an average PPFD of 900-1,000 with extremely high uniformity over a 4’x4. Far from the 387 figure your published.

We’ll ignore (for now) the entire spectrum discussion on white light/purple light (but for those interested, we suggest this article by Qingwu Meng, a Ph.D. student in Horticulture at Michigan State University.

We appreciate your attempt at a fair comparison, but it’s not fair. If you’d like to increase your credibility, please try again using the manufacturer’s recommendations. Until then, we’ll assume this was an attempt to prey on uneducated consumers.

@Theo, thank you for weighing in. It’s important that we keep everyone honest. Cheers.



Gladly. The price is a comparison of the price per umol s-1 output initial investment. Yes, per fixture it is less than double, but your fixture has less output because it is a lower wattage (though a higher initial efficiency):

It’s 1100 umol over $810, and for us 2000 umol over 450. To be fair we have 3% losses per year on the lamp, so that should be average 1,5% lower average, but LED also has losses over her lifetime, though a little less per year. You could argue that the fixture output us average actually lower, however we can boost the lamp 15% to a higher output at the same efficiency, so per fixture we could go way over 2100 umol with boosted output, which is frequently used. I did not take that into account in the comparison, but rounded it to 2000 umol. Even with a bit lower output it would be about 3x the costs per initial umol light that you need, again not taking our boost feature fully into account

Take into consideration though , this is an investment overview, not a running costs overview. There will be reflector and lamp changes so our running costs are higher, also because we use a bit more electricity. I have a different comparison for that, I was purely talking investment costs to put the initial costs into perspective. The running costs on the other hand should also take into account current present value and interest costs over the investment, so it’s quite a complex calculation. If you wish we can compare notes and discuss this in a different topic. Will probably see you in Vegas, right? Happy to sit with you and compare.

Of course you have the advantage with the Spydr of the multi-layer applications etc, so in a comparison there is much more to it than just looking at price or running costs. However, initial investments, specifically for a large project, should not be overlooked. I made this comparison to explain the “logic” in the Kind LED comparison against other brands that do publish accurate PPF of their fixture.


I’m not shooting the messenger, I’m shooting at the message :wink:


As long as you don’t accidentally hit any bystanders :slight_smile:


Ah - PPF/$. Thank you for clarifying. You’ve already preempted my comment about how PPF/$ is just one variable so I’ll save my pitch for now. :slight_smile:

I won’t be Vegas this year (as of this writing), but it’s a good conversation we should explore. Maybe in another post or podcast - would make for a healthy discussion. -TW


:smiley: not if they are innocent

I don’t think that we see things a lot different. It’s a complex discussion and you can talk about it for weeks. There are so many factors you can and/or should take into account. But let’s face it: basically it is about the bottom line and initially what you can spend and how you can spend it.

I think we also agree that there are a lot of LED products on the market that do not perform as advertized, and are extremely hyped by non-science. There is no such thing as alternative facts.


This is the quote of the day! :+1:


Continuing the discussion from PPFD Grow Light Comparision:

TL;DR (too long, didn’t read): Comparisons of grow lights are necessary and important for consumers but light is a tricky topic. Spreading misinformation willing or unwittingly has the same negative effects. We should do our best to keep basic principles and physics in mind when doing these studies.

Discussing light and lighting fixtures is not a trivial topic. I started my degree in optical engineering 4 years ago and still find myself consulting text books and my notes regarding light. That’s why I think grow light comparison videos are a great way to untangle difficult vocabulary and concepts around lighting for growers and consumers alike. However, after seeing a few of these videos, there tends to be some amount of myth and mystery weaved into each one.

I want to first thank KIND LED for taking the time to put together this video and then share it to the community. I do believe that addressing lighting concerns for controlled environment agriculture is one of the major paths toward a sustainable alternative to traditional ag.

To start, it is indeed important to distinguish between photometry and raidometry. However, the definition for radiometry provided is lacking quite a bit and these two topics end up getting crossed later in the video. Radiometry is the measure of electromagnetic radiation from a source or on a target in space. With radiometry we are able to understand the light distribution from a source or on a target in both angular and spatial extend as well as the transport of light from source to target.

@3:00 there is a quote “Photosynthetic receptors in plants are activated by the photon itself, not the energy contained within that photon.” A photon is a quantized unit of electromagnetic (EM) radiation and has no mass, it is pure energy. A photoreceptor takes incident EM energy and converts it into an internal signal. That signal drives a number of processes, photosynthesis being the most well known.

@9:08 referencing white LEDs and their green/yellow content, you say “Many of these photons will be reflected by the plant.” This is a very dangerous statement in a video such as this. There is a ton of stuff packed into that statement. When light is incident on a surface it can transmit, absorb or reflect. Green light is highly transmissive in leaves! This is how shaded leaves actually survive while trying to grow into better quality light. Saying that “many” of these photons reflect from the surface is very misleading. The amount of light reflected is dependent on the index of refraction of the leaves. Furthermore, there are cartenoids that have absorption peaks in this green and yellow range. With so many variables at play, generic statements like this are dangerous because it’s easy to take these statements at face value.

It’s great to openly discuss various topics and analyze grow light systems but caution needs to be taken with what information is spread. Physics gives us the tools to help us understand how light quality and quantity affect the plants we care so much about, so I just think we should care equally about how we interpret and use these tools.


Why not add this response in the topic discussing this video? I believe the issues you talk about have already been addressed.

As for photosynthesis and photons: I actually agree with Kind LED that the photosynthetic process is based on the number of photons, and not on the photon energy.

Comparisons like this are not helpful, as they do not integrate the light of the fixture on the surface. It would be a good start if LED manufacturers started to publish the PPF of their fixtures, instead of the ridiculous PPFD-at-distance variables. Serious manufacturers do.

You can only guess why a lighting manufacturer shows their comparisons like this, with such a bold disregard for lighting science. Either they are not educated or willfully misleading their customers. Both are extremely bad for the industry.

1 Like

Hello, fellow optical science PhD student here, wanted to clear something up that seems to be a common misconception. Light is electromagnetic energy. Like shibbyhockey04 said, a photon is a quantized unit of that energy. A single photon has energy equal to the frequency of that photon multiplied by h-bar (planck’s constant). image

Therefore, a single wavelength source has total energy equal to the number of photons emitted by that source multiplied by the energy of a single photon at that wavelength.

For a broadband (multiple wavelength) source, the total energy emitted is equal to the sum of the energy contributions from each discreet wavelength.


From this we can see that although PPF and PPFD are important factors to keep track of, it is an almost meaningless number when decoupled from the emission spectrum of the source in question. For example, a light can be advertised as having the highest PPF on the market but if all of those photons are at unhelpful wavelengths then it wont be a good grow light. Even though PPF already restricts us to the photosynthetic wavelengths, plants do not respond evenly across that spectrum. Plants absorb specific wavelengths more efficiently than others, which is also cultivar dependent.

Hopefully this explains why it is incorrect to talk about photons and energy as if they are different, decoupled things and that PPF is only a useful metric when referencing a normalized spectrum.


Unfortunately the original thread was locked so I opened up a new topic to comment. And you are correct there were some great replies to various aspects of the video @Theo.

A video that quantifies the total fixture output (integration of illuminated energy in PAR region) and then correlates PPFD measurements, with sufficient sampling, would be a more accurate comparison video. PPFD measurements with varying fixture heights hold value in describing how the fixture output is distributed over a given area. In this context, I’m stating these videos do have merit in education and product differentiation.

My point is simply that with these comparison videos, manufacturers must be careful in presenting this information to the community, especially fundamentals, correctly. Grow light comparisons in terms of light quality, light quantity, and radiometric distribution allow growers to make an educated decision on what fixture is best for their space. As I prefaced in the original comment, this is a challenging subject! Mistakes will happen and we the community have the ability to vet this information. An open comparison and discussion over clearly defined metrics and testing methods is tremendously beneficial to those using the products.