Gavita Pro DE vs. ePapillion: irradiance uniformity results

Beta Test Team · Nov 30, 2014

The following irradiance figures show uniformity over a 3'x3' area with the lamp 3' from the center.

Reflected photons off of walls, ceiling, and floor are not part of these measurements. Also not part of the measurements is overlapping radiation from other luminaires, as is commonly found in growth rooms, chambers, and greenhouses.

The second figure are all 1000W luminaires, well, at least that's true for Gavita and ePapillion.

It seems safe to say the ePapillion, with its less focused footprint, is better suited for 'lighting the room,' not the canopy. And Gavita Pro DE is better suited for 'lighting the canopy,' not the room, with its greater focused footprint. In other words, ePapillion irradiance is lower but its uniformity is greater, and Gavita Pro DE irradiance is greater but its uniformity is lower.

I included the last figure to show typical LED and Greenbeams (Cycloptics 315W) uniformity, as well.

These data were calculated using this method: https://www.cycloptics.com/sites/default/files/USU_functional_efficiency.pdf

http://cpl.usu.edu/files/publications/poster/pub__3942523.pdf

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0099010

Picarus · Nov 30, 2014

very interesting, thank you.

Beta Test Team · Nov 30, 2014

You're welcome. I too find it very interesting. I think the more unbiased data collected and compared, the better.

For too long Cannabis growers have been using assumptions and biased unsubstantiated marketing claims to make decisions, which were often not based upon good science or scientific understanding. Hopefully that time is near its end.

Another thread you may like I wrote, on the topic of using unbiased data for comparisons is this one (fair warning: lots of off-topic posts therein, sadly):

"LEDs vs. HPS lamps: A reality check"
https://www.icmag.com/ic/showthread.php?t=296665

HUGE · Dec 1, 2014

Keep up the good work.

habeeb · Dec 1, 2014

like that little test setup,

but 1000 are not used in 3x3, 4x4, so would the numbers differ. also what about measuring the cycloptics in a setting such as the open air you have, as I have heard some people running them in 3x3 space

also what does happen if people are using in a tent, I'm sure the numbers come out better, as this setting is more for one lamp open air, ( which I don't know anyone running a 1k in the middle of their basement all alone ) as most commercials are going to overlap with a back wall, and wall at the end clearing up the side that doesn't have the overlap lamp .. why not remeasure in a 4x4 tent as I'm sure you have one laying around with that many lamps?

man I'm really trying to compliment you as you seem to push for knowledge and want to bring people more info.. but what am I gonna do with this info, as no one is running a 1k in open air solo, show us a pic of a gavita vs. epap grow side by side and that will generate 1000x times more interest then data that is un-used, so what's that take, 2 months to get some conclusive results who is actual king in real world results. I mean are you using this data to hypothesize your next grow outcome??

Beta Test Team · Dec 1, 2014

habeeb said:
like that little test setup,

but 1000 are not used in 3x3, 4x4, so would the numbers differ. also what about measuring the cycloptics in a setting such as the open air you have, as I have heard some people running them in 3x3 space

1000W luminaires are used however best suits the grower, and in many cases 4'x4' isn't optimal, but it is the de facto suggestion by growers to other growers. These data show what one luminaire provides in terms of 'footprint' uniformity.

I presume they used meter squared because it's the common area used, for example, to define irridiance (PPF) or lux.

To get a good idea of what the uniformity looks like over a 4'x4' area just extend out the line at both ends (following the line's trend). In most cases, except for the Cyclotpics, that would be an additional reduction in PPF the further from the center one measures. The numbers would be exactly the same as they are now, they would just be extended by 6" each direction.

I'm not sure what you mean by measuring the Cycloptics. They're all measured the same way, see the first picture. These measurements don't account for reflected photons, nor overlapping photons (from other luminaires).

habeeb said:
also what does happen if people are using in a tent, I'm sure the numbers come out better, as this setting is more for one lamp open air, ( which I don't know anyone running a 1k in the middle of their basement all alone ) as most commercials are going to overlap with a back wall, and wall at the end clearing up the side that doesn't have the overlap lamp .. why not remeasure in a 4x4 tent as I'm sure you have one laying around with that many lamps?

These data were collected by Dr. Bugbee and Dr. Nelson. Not by us.

Like I wrote, these data don't account for reflected photons. So please, stay on topic. And start a new thread if that's what you want to discuss.

Like I wrote to you in the other thread, these measurements are not trying to account for every factor. Just those most useful over a broad range of applications.

habeeb said:
man I'm really trying to compliment you as you seem to push for knowledge and want to bring people more info.. but what am I gonna do with this info, as no one is running a 1k in open air solo, show us a pic of a gavita vs. epap grow side by side and that will generate 1000x times more interest then data that is un-used, so what's that take, 2 months to get some conclusive results who is actual king in real world results. I mean are you using this data to hypothesize your next grow outcome??

There is a lot to consider from these data and a lot to make use of, consider if you will a large room (40'x40') filled with canopies. If you're seriously interested in why these data are useful as is, I will write more. But for now I'll just wait and see.

Mister_D · Dec 1, 2014

for sharing more data :biggrin:

I can definitely see some potential uses for the information presented, but I do have a couple questions.

1. Is the photon distribution graph an average of all the measurements at X distance from the bulb for a given reflector? For instance measurements are taken 0.5m from the center of front, back, and sides of the bulb. I seriously doubt all these data points were the same, so is the graph representative of the average of all these points?

2. Do you know what sunsystem reflector was tested?

Beta Test Team · Dec 1, 2014

Mister_D said:
for sharing more data I can definitely see some potential uses for the information presented, but I do have a couple questions.

You're welcome. Dr. Bugbee is really an amazing scientist - the breadth and depth of his work is more than impressive.

Mister_D said:
1. Is the photon distribution graph an average of all the measurements at X distance from the bulb for a given reflector? For instance measurements are taken 0.5m from the center of front, back, and sides of the bulb. I seriously doubt all these data points were the same, so is the graph representative of the average of all these points?

Yes, that is my understanding, except there were only three lines of measurement (see the solid lines in the right-hand side of the first figure in the first post). A 'side-view' of sorts. Also, another improvement in their work would have been more data points. We would have made many more measurements, but then, that's really tedious.

That said, the difference between these data and two different side-views would not be large in most cases.

Here is what the athors wrote about their method:

Measuring functional light efficiency

Accurate quantification of light requires sufficient resolution to capture the variations that occur due to the non-uniform output of the lamp and luminaire, especially near the center. To reduce the number of measurements while maintaining good resolution, points were 2.5 cm apart in the center and increasing to 10 cm apart near the ends.

Radial integration over the surface allows fewer measurements by taking advantage of the radial symmetry of light scatter. Measuring three straight lines through the center directly below a level lamp provided enough data for a good approximation.

Here is what the authors have to say about the third figure in my first post, which holds true for the second figure in my first post, as well:

Lighting technologies vary widely in how radiation is distributed (Figure 1). There is no ideal pattern of radiation distribution for every application. In large greenhouses with small aisles and uniformly spaced plants, the broad, even output pattern typically emitted from HPS fixtures provides uniform (little variation over a large area) light distribution and increased capture of photosynthetic photons. In smaller greenhouses with spaced benches, the more focused pattern typically found in LED fixtures can maximize radiation transfer to plant leaves.

As the area (height of width) covered by plants increases, the need for more focused radiation decreases (Figure 2).

Figure 1. The photon distribution of four fixtures with similar photon efficiency.

Each line represents a cross section of the photon intensity below the fixture. The LED fixture (Lighting Sciences Group) uses optics to achieve a narrow distribution, with the majority of the photons falling in a concentrated pattern directly below the fixture. Conversely, the Cycloptics ceramic metal halide fixture is designed for even light distribution, and therefore casts uniform radiation over a large surface area. Since the area increases exponentially as the distance from the center increases, an equal photon flux farther from the center represents a larger quantity of total photons.

Mister_D said:
2. Do you know what sunsystem reflector was tested?

Sun Star, well, at least for the third figure in my first post. I'm not sure what model was tested in the second figure in my first post, nor its wattage. I think the second figure shows results from something other than the Sunlight Supply Sun Star, due to the differences in results between the second and third figure in my first post (and the one below, as well).

Here's the list of brands and models used for the third figure in my first post:
http://www.plosone.org/article/fetc...ri=info:doi/10.1371/journal.pone.0099010.s001

I have attached the 400W results for the Sun Star, as well (below). However, note that the lamps in the following figure were hung 0.7 meter above the floor, not 1 meter as in the figures in the first post.

Beta Test Team · Dec 1, 2014

So to write a little about 'lighting the room' vs 'lighting the canopy,' this figure shows "canopy photon capture efficiency." That is, what percentage of the total photon (energy) footprint is irradiating leaves. Obviously, the greater the canopy photon capture efficiency percentage the greater the radiation use efficiency, which means less wasted light.

This figure shows how narrow and short canopies are better suited to be irradiated by luminaires with greater focused energy (like LED), while wider canopies are better suited for HID luminaires, for example, Gavita, and yet, even wider canopies are better suited for HID like ePapillion and Cycloptics. Though again, these data don't account for effect from reflected photons nor overlapping photons from other luminaires. And generally, as the canopy get taller LEDs are less well suited for the canopy:

Figure 2: Canopy photon capture efficiency.

As the plant growth area under the fixture gets smaller, wasted radiation often increases. This figure illustrates the concept of canopy photon capture efficiency. Two meters was chosen as a typical mounting height, but this can be scaled as a unit-less ratio. Multiple overlapping fixtures are typically used to minimize PPF variation over a large area.

A good goal for efficient use of photons is at least 70% photon capture efficiency. And if one includes reflected photons (off of walls, floor and ceiling) in a high quality growth room or chamber, the photon capture efficiency can be increased greatly - but doing so isn't feasible for most luminaires (a notable exception is Greenbeams, which used computer modeling of the growth area).

An associated efficiency metric we use is what we call space use efficiency, in terms of canopy area to floor area. This tells a grower how much area is taken up by empty floor space (no canopy), such as walkways, equipment, etc. Generally, the lower this efficiency the better suited luminaires have more focused energy output (footprint), and the higher this efficiency the better suited lumianres have less focused energy output.

Mikell · Dec 2, 2014

Beta Test Team said:
You're welcome. Dr. Bugbee is really an amazing scientist - the breadth and depth of his work is more than impressive.

Indeed. After reading you quote his name a few times, I noticed that two of the studies I use to try and convince peppers growers that spectrum does matter, were conducted in part by Bugbee.

He's on RG as well, and thankfully makes the majority of his studies immediately available for download.

As always, your contributions are much appreciated.

flat9 · Dec 2, 2014

This seems to be in line with what Grower's House was reporting:

http://growershouse.com/images/DE_TEST_INFOGRAPHIC.pdf

Beta Test Team · Dec 3, 2014

Thanks for adding that link, and good point, they all do comport pretty well.

flat9 · Dec 4, 2014

What was the LED fixture you tested in that infographic up there?

Beta Test Team · Dec 4, 2014

We didn't do the testing, but the LED you're referring to is the Lighting Sciences Group "Violet" model. Here's their website: https://www.lsgc.com/

Looking at that site now, they have what they call "high bay" LED, called "VividGro," maybe that's the same one under a different model name? https://www.lsgc.com/products/fixtures/vgrohb/

flat9 · Dec 4, 2014

Kind of off topic, but I feel LED may be commercially viable if you order from China and also get smaller units and more of them. The Houyi w/ 120 degree reflectors w/ 75 watt COBS in 2 x 2 arrays seem promising in that regard. For what it's worth, here's what Houyi gave me at 12" from canopy for their 4 x 4 model (draws 610 watts). Their numbers, so not sure if it's legit. I'd love to do a test on my unit but I don't have a spectrometer nor do I want to splurge for one.

whazzup · Mar 2, 2015

First of all, a grid test is useless. We do not light a 3x3 or a 4x4 grid. Secondly, the representation of how HPS is used over beds is ridiculous. Of ourse you do not throw away you light like that. In a modern greenhouse or climate room you use rolling benches and light wall to wall with HPS. You do not just light the top of your plants, but you provide good vertical and horizontal penetration. There are no paths in a modern grow room, only perimeter paths.

The suggestion that you should use our fixture over a 4x4 area is insane. First of all it is not a square field reflector and secondly you are more looking at two square meters of surface for 1000 umol. You will totally oversaturate your crop in a 4x4 grid and create hotspots by too much overlap on the sides.

The same mr Bugbee btw suggests in his caculations that LEDs use 50% of energy compared to HID lamps. I dare you to find a led lamp that produces 3.5-4 umol per watt. 1.7 is more the standard.

Check your sources and go take a look in a professional operation.

Attached is a polar distribution diagram of the HR96 reflector.

Beta Test Team · Mar 2, 2015

whazzup said:
First of all, a grid test is useless. We do not light a 3x3 or a 4x4 grid. Secondly, the representation of how HPS is used over beds is ridiculous. Of ourse you do not throw away you light like that. In a modern greenhouse or climate room you use rolling benches and light wall to wall with HPS. You do not just light the top of your plants, but you provide good vertical and horizontal penetration. There are no paths in a modern grow room, only perimeter paths.

The suggestion that you should use our fixture over a 4x4 area is insane. First of all it is not a square field reflector and secondly you are more looking at two square meters of surface for 1000 umol. You will totally oversaturate your crop in a 4x4 grid and create hotspots by too much overlap on the sides.

The same mr Bugbee btw suggests in his caculations that LEDs use 50% of energy compared to HID lamps. I dare you to find a led lamp that produces 3.5-4 umol per watt. 1.7 is more the standard.

Check your sources and go take a look in a professional operation.

Attached is a polar distribution diagram of the HR96 reflector.

Hi whazzup. You may like to see my comments about your misunderstandings below. For example, PPF (and PPFD) is irradiance over a meter squared:

https://www.icmag.com/ic/showpost.php?p=6830072&postcount=600
https://www.icmag.com/ic/showpost.php?p=6830096&postcount=601
https://www.icmag.com/ic/showpost.php?p=6830129&postcount=602

Also, there are paths (walkways) in many "modern grow rooms," like say, the huge operations out here in the US. I know this personally, as I have designed and seen designs for huge warehouses, well above 20,000 sq. ft. of canopy area - they all have walkways, throughout the room, as well as along the walls ("perimeter paths"). The designs are highly space efficient, as well as work efficient, which is an important factor to consider when you're dealing with thousands of plants a time.

Having walkways also is beneficial in terms of irradiance in the canopy, so lower branches get bigger buds, rather than having a completely closed canopy over the entire room like you're suggesting. Also, many growers grow so-called "trees," where moveable trays are not appropriate.

And like the old saying goes, "there's more than one way to skin a cat." A value you should look into is what I call "space use efficiency," which is the % of total floor space in a grow room taken up by canopy area. The greater this value the better, as long as work efficiency doesn't suffer (which can happen with plants on moveable trays).

That figure you posted isn't the whole story, sorry to say. The data in this thread speaks for itself.

Beta Test Team · Mar 10, 2015

About Gavita vs. ePapillion, I totally neglected to mention that the ePapillion actually emits more umol/s within PAR than Gavita, by about 1%.

ePapillion = 1,767 umol/s in PAR range emitted from the fixture.
Gavita = 1,751 umol/s in PAR range emitted from the fixture.

So ePapillion emits a little more useful radiation than Gavita. However, when accounting for input watts (joule/s), both fixtures have a photosynthetic efficiency of about 1.7 umol/s per joule within PAR range.

Here is something I wrote to someone about this topic, when he asked me why I suggest ePapillion instead of Gavita, when tests like Growers House show Gavita has greater averaged umol/s over a 4'x4' area or 5'x5' area:

It's mostly about uniformity, which is more important than umol per fixture per area. Basically, simply in terms of umol the Gavita provides more than ePapillion in a 5'x5' (or 4'x4', etc.) area due to the greater spread of the ePapillion, which is why ePaillion has much better uniformity. And in fact, ePapillion fixture emit more umol than from than Gavita by about 1%. But Gavita's reflector produces a much greater hot spot than ePapillion due to Gavita's design, which means more of its total output is focused within a smaller area (leading to greater umol values you mentioned), but that isn't a good thing when working with large rooms.

Those claims about Gavita providing much more umol are simply wrong in the context of what's important (umol uniformity). And the average umol over 5'x5' doesn't matter because Gavita and ePapillion fixtures should be spaced much closer than on 5'x5' centers for worthwhile uniformity.

I believe the basic ePapillion fixture layout they suggest is:
-- About 3.5 feet between fixtures (measure from center of lamp to center lamp) along a row and about 6 feet between rows, with additional fixtures along the canopy edges (the canopy area is not taken into account)

I believe the basic Gavita fixture layout they suggest is:
-- About 2.5 feet between fixtures (measure from center of lamp to center lamp) along a row and about 7 feet between rows, with additional fixtures along the canopy edges (the canopy area is not taken into account).

whazzup · May 23, 2015

Go read high times magazine in July for the DE test.

As for light spacing: here is how it is done. Have you ever seen a lights interaction calculation with a bigger grid than just between the center lights? That may be good for greenhouses, but not for climate rooms. We calculate room uniformity, not just in the center.

https://www.dropbox.com/s/ahg4wvcoqgdqtt5/sample light calculation for Howard Steven Soto.pdf?dl=0

Why paths?
https://www.dropbox.com/s/vtryce1slvfleo8/img_1068.jpg?dl=0

LargePrime · May 23, 2015

Beta Test Team said:
About Gavita vs. ePapillion, I totally neglected to mention that the ePapillion actually emits more umol/s within PAR than Gavita, by about 1%.

I appreciate your work BTT. And I can get all uptight when people call me out. But with love, i call horse shit.

There is no way your confidence in this number, or this testing, can allow you to say with a high degree of confidence that there is any appreciable difference between these reflectors, if you are being honest. Statistically you would need to test several hundred randomly selected reflectors to even get close to "1% accuracy" with any meaningful confidence. And you would need quite a few other people repeating this same test to do it with any degree of confidence that a third party should respect. there are all kinds of biases in a one man operation that make it hard to have confidence in the results.

I mean just looking at your significant figures there is a problem. And you have how many quantum detectors to verify which one is lying?

Now DO NOT THINK I am shitting on what you are doing. Just the opposite. Who the fuck else is doing this BASIC science we need except you! And who is giving it AWAY!? The work you do is real and important, IMHO.

Gavita Pro DE vs. ePapillion: irradiance uniformity results

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