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Tests of different DIY household bulb solutions

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Howdy farmers!

I recently tested the PPFD (umol/m2/s) of a few different generic household bulbs to figure out how they perform compared to each other at a certain height. As we (humans) can perceive a lamp to be very bright, plants can sometimes experience a different reality. I also tested a couple of homemade reflectors and how they affect a lamps light footprint.

Here is a link to a blog post I wrote about the test if anyone wants to read the summary.
https://www.ledtonic.com/blogs/guid...ht-test-ppfd-amp-footprint-for-indoor-growing

I am currently in the process of gathering new lamps and bulbs to test and I am wondering if any of you have any ideas of what would be interesting to test? Is there any regular generic type of household light that would be interesting to know the output and footprint of? Is there any lamp out there that is not intended for growing, that many still use for that purpose?
Bulbs_PPFD_Results.JPG


I have an idea that the propagation/seedling period and maybe even early veg-period, could potentially be covered with a small bulb when the intensity requirement is low (50-300 PPFD). There is a possibility to save some electricity in the process, save some additional heat from being produced, and save some hours from being taken of your big and expensive grow lamps' life.
If the plants' canopy hasn't yet reached the size of 1inch x 1inch (2,5cm x 2,5cm), we might not need to light up a whole room in the process of keeping that sucker alive at that size.

Obviously, this idea is based on that you only need to light up a small area of only one plant or a couple of small plants in small pots. A big lamp is obviously more practical if you have a big area to illuminate.

I'd love to get input from you guys :)
 

Ina

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I'm trying floodlights(for now only for veg but I made few seeds under it as well,it wasn't for the size of the buds ,just for the seeds).Also tried few types of LED bulbs but they were 35w each,not the usual 10 to 15w.CFL also above 48w each.To be sure:) I prefer them to be as strong as possible.Now these days I found 100w LED bulb(6400,3200k they had both colors)but I have nothing to grow under it.For veg I am positive all the cheap,not grow LEDS can perform fantastic.I discontinued to use CFLs but they were also fine….I just don't want to broke them in my house,LEDS are safer:)
 

Ina

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and save some hours from being taken of your big and expensive grow lamps' life.
I also think so.....You can choose expensive light especially for flowering than(this is what I am gonna do eventually),not grow under 3200k all the time for example but start under something cheaper 4500-6400 that doesn't produce so much heat……...Because for veg you don't need much and plants growing vigorous with these.Another member(az2000)showed that flowering also can be done really well.
 
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.I discontinued to use CFLs but they were also fine….I just don't want to broke them in my house,LEDS are safer
I agree. I was a little sceptical to remove the protective dome/diffuser on the CFLs when I found out that they were made of glass. There was no super safe way to do it. I crushed the first lamp by hand but the other two I carefully sawed of with an angle grinder. Just touching the glass made them break right away in super small pieces and I found that to be a lot safer. The domes on the LEDs were made of plastic and were a lot easier to remove by first puncturing them with a knife and then just squeeze hard until the silicone holding it will let it go (for anyone wondering or having the same issues).

Floodlights sound like a cheap and easy option. great idea :)
 
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Wow, epic! I could really recommend the grid that I use in the video (at 19:35)
It is a grid made for compost but the e26/e27 lamp holders fit perfectly in there and can easily be tightened to it, they can be positioned anywhere you want them, moved around, and added one by one when your plants grow and need for light increases.
 

Ina

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20s for 200w(real,not equal) floodlight?O,it will be fantastic! but I think 20 dollars is the cost of way lower watages,about 50w and such.But I will check.That reminds me you can get few smaller units with different color temp,for example one warm and two cold white or...….
 
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I agree. I was a little sceptical to remove the protective dome/diffuser on the CFLs when I found out that they were made of glass.
A few years ago I grew with household LED lightbulbs, and documented some things on a blog. I made some measurements of the difference between lightbulbs with/without the diffusion globe, mounted in reflectors or not. I used an inexpensive lux meter (because I wasn't motivated enough to buy a real PAR meter. Plus, it's all white light. I think it's fairly comparable in terms of lumens. If it was blurple light, lux/lumens wouldn't be.).

Anyway, the blogs disappeared. But, I had copies of them. I'm in the process of putting the info on my Google Drive:
https://drive.google.com/open?id=17eMlIDRQFDN0_0XAyrJyh-44NVBhXLz-

There will be 6 articles. Until they're all up, some interlinking inside the documents won't work. You might like the first document which compares lightbulbs.

Another member (az2000) showed that flowering also can be done really well.
Ina is referring to this post <<link (in the "COB vs gram-per-watt rule" thread). It doesn't discuss how I do it much (that will be the articles mentioned above). But, it shows photos of the plant in flower & the harvest.

Note: I said in that post that I was using 28w-32w/sq ft of lightbulbs. However, reviewing my notes fromback then: it was 18w-22w sq ft. That's very low light/energy, especially for flower. I was keeping it low to see how efficient these bulbs are. (I actually believe that surrounding a plant with light adds efficiency compared to supplying all the w/sq ft from a concentrated location from the top.). I.e., if I had all those bulbs mounted to a board hanging above the plant, I think I would have needed 28w-32w/sq ft. (But, juggling managing/positioning many individual sockets is tedious. It's not bad growing one plant. But, if I had 4 plants in a 4x4 tent, that could turn into a full-time job.).

PS: I haven't watched your video yet. I'll reply further when I do. I'm sure it's great stuff! I think more people should grow with these bulbs. Either supplementing/sidelighting in flower. Or, new growers who don't want to spend a lot of money on lights (before knowing they can grow. They can scale into light this way. And, use them for sidelighting if/when they buy a "real" grow-light fixture.).
 
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A few years ago I grew with household LED lightbulbs, and documented some things on a blog. I made some measurements of the difference between lightbulbs with/without the diffusion globe, mounted in reflectors or not. I used an inexpensive lux meter (because I wasn't motivated enough to buy a real PAR meter. Plus, it's all white light. I think it's fairly comparable in terms of lumens. If it was blurple light, lux/lumens wouldn't be.).

Anyway, the blogs disappeared. But, I had copies of them. I'm in the process of putting the info on my Google Drive:
https://drive.google.com/open?id=17eMlIDRQFDN0_0XAyrJyh-44NVBhXLz-

There will be 6 articles. Until they're all up, some interlinking inside the documents won't work. You might like the first document which compares lightbulbs.



Ina is referring to this post <<link (in the "COB vs gram-per-watt rule" thread). It doesn't discuss how I do it much (that will be the articles mentioned above). But, it shows photos of the plant in flower & the harvest.

Note: I said in that post that I was using 28w-32w/sq ft of lightbulbs. However, reviewing my notes fromback then: it was 18w-22w sq ft. That's very low light/energy, especially for flower. I was keeping it low to see how efficient these bulbs are. (I actually believe that surrounding a plant with light adds efficiency compared to supplying all the w/sq ft from a concentrated location from the top.). I.e., if I had all those bulbs mounted to a board hanging above the plant, I think I would have needed 28w-32w/sq ft. (But, juggling managing/positioning many individual sockets is tedious. It's not bad growing one plant. But, if I had 4 plants in a 4x4 tent, that could turn into a full-time job.).

PS: I haven't watched your video yet. I'll reply further when I do. I'm sure it's great stuff! I think more people should grow with these bulbs. Either supplementing/sidelighting in flower. Or, new growers who don't want to spend a lot of money on lights (before knowing they can grow. They can scale into light this way. And, use them for sidelighting if/when they buy a "real" grow-light fixture.).
Sweet information and pictures! Very informative and great looking. I love that you are experimenting and those lamp-splitter arms looks super handy.
I will dive deeper into that again later on :) thanks for the links.

I've just seen so many use household bulbs without really knowing how much they put out and how far away to place them from leaf surface/canopy at different stages. My goal is to provide thorough horticultural information to lighting technology not made for the purpose of growing, as it is so widely used. We should produce photons wisely and make the best use of them, at the right distance and quantity. I've seen multiple grows with one or two 23w CFLs hanging a foot above the canopy, producing plants that are falling over and I just think that some education in intensity and footprint could help a lot of people out there.
Many stare themselves blind on drawn wattage and lumens, which a plant cares nothing about if none of the light is actually reaching its leaves.
But it makes sense since the average Joe doesn't have a LUXmeter laying around (or even better, a quantum sensor).

The video is really made for anyone that wants to grow anything, but could also apply to an experienced cannabis grower.
 
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But it makes sense since the average Joe doesn't have a LUXmeter laying around (or even better, a quantum sensor).
I'd love to see a comparison of the PAR/watts for different household LED lightbulbs. I've always wondered if one brand has a better spectrum. PAR/w would reflect that (much less costly than a spectrometer).

I measured lux (lumens falling on a spot) because I figure household LED lightbulbs don't vary much in their "spectrum." I've used Phillips, GE and Cree. None have stood out to me as better or worse (in terms of what I see in the plant's growth). But, there probably is differences.

Like you said, I think people focus on watts, or just what a lightbulb's label says (which is lumens radiated into space, not representative of reflecting the light). There's *so* much that can be done (like removing the diffusion globe; reflecting; distributing the watts around the plant vs single-source top-down lighting). All those things create efficiency more than a better binned diode. The way household LED lightbulbs have their LEDs facing the same direction. Removing the plastic diffusion globe is a 300% improvement (without even using a reflector). To me, that's like low-hanging fruit. $5 and a hacksaw -- and you're delivering a ton of cheap light to the plant.

I really believe distributing the watts around the plant creates a significant efficiency (compared to top-down, single-point lighting). That was one thing I found demotivating about the way grow-lights adopted COB LED technology. I'd rather have a large fixture with 100 3w diodes than a single fisheye. (I'd rather have two fixtures with 50 3w diodes, etc.).

I actually had the idea (but never the motivation to try this): insert LED strip lighting *into* the canopy! Light it from within. Keep inserting 2w strips as the plant grows. The idea being to feed each leaf directly.

That's probably taking a good idea (distributing watts around the plant for better coverage) to an extreme. But, there are low-watt "corncob" bulbs made with SMD5630. Those are fairly efficient diodes @ 110L/w. (They were 3-4 years ago, the last time I looked into this topic.). I've always wondered how inserting some of those into the canopy might help. They're not powerful enough to burn/bleach. Everything I've seen (surrounding a plant with light) makes me think that could be a real winner. Instead of surrounding the plant with watts, insert a few within it!

But, it would be nice to have *definitive* knowledge of which household LED lightbulb has the best spectrum (best PAR output).

I got out of this topic 3-4 years ago. The lights definitely produce. I got dense buds, and the smoke was potent. I don't know many people who would complain. But, it lacked something compare to T5HO and CMH. Something about the UV, I think. I planned to buy a PAR meter and continue adding data to those documents I linked to. In fact, I was liking the lightbulbs better than the typical LED grow-light fixtures because it seemed less "secret sauce."

A lot of the grow-light fixtures are hyped. They could be better than others. But, you never know for sure. Instead of hundreds of dollars for a proprietary "trust me" fixture, $5 for a lightbulb. It seemed very counter-culture (compared to what everyone was doing). You have your kelvin color temperature available to you. You have distributed watts around the plant (a far greater efficiency than any secret-sauce spectrum). It's like the opposite of what people are doing. Simple, cheap, locally available at any hardware store. No man behind the curtain.

I still recommend it to new growers. It's definitely cost-efficient for sidelighting/supplementing "real" fixtures.

Do you have the same Philips LED & GE Brightstik lightbulbs where you're at? I'd really like to know if one has a better spectrum than the other (i.e., PAR/w). That's the one unknown ("trust me") about this. I've seen them grow very well at 20w/sq ft. I assume the spectrum must be good. But, it's still an unknown.

PS: I'm going to have the flexible/spider fixture "how-to" put up in the next day or two. That will be the last of the blogs I had (my accumulated thoughts back when I was doing this stuff.). Check the folder for that later. You're welcome to use any of that.
 

Ina

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313
Sweet information and pictures! Very informative and great looking. I love that you are experimenting and those lamp-splitter arms looks super handy.
I will dive deeper into that again later on :) thanks for the links.

I've just seen so many use household bulbs without really knowing how much they put out and how far away to place them from leaf surface/canopy at different stages. My goal is to provide thorough horticultural information to lighting technology not made for the purpose of growing, as it is so widely used. We should produce photons wisely and make the best use of them, at the right distance and quantity. I've seen multiple grows with one or two 23w CFLs hanging a foot above the canopy, producing plants that are falling over and I just think that some education in intensity and footprint could help a lot of people out there.
Many stare themselves blind on drawn wattage and lumens, which a plant cares nothing about if none of the light is actually reaching its leaves.
But it makes sense since the average Joe doesn't have a LUXmeter laying around (or even better, a quantum sensor).

The video is really made for anyone that wants to grow anything, but could also apply to an experienced cannabis grower.
That also looks nice and easy(and on topic) but I think,like you mentioned ,that it can be positioned way lower judging by the plants stretch.....But its cool:)https://www.thcfarmer.com/threads/super-cheap-led-veg-light.93296/
 
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I'd love to see a comparison of the PAR/watts for different household LED lightbulbs. I've always wondered if one brand has a better spectrum. PAR/w would reflect that (much less costly than a spectrometer).

I measured lux (lumens falling on a spot) because I figure household LED lightbulbs don't vary much in their "spectrum." I've used Phillips, GE and Cree. None have stood out to me as better or worse (in terms of what I see in the plant's growth). But, there probably is differences.

Like you said, I think people focus on watts, or just what a lightbulb's label says (which is lumens radiated into space, not representative of reflecting the light). There's *so* much that can be done (like removing the diffusion globe; reflecting; distributing the watts around the plant vs single-source top-down lighting). All those things create efficiency more than a better binned diode. The way household LED lightbulbs have their LEDs facing the same direction. Removing the plastic diffusion globe is a 300% improvement (without even using a reflector). To me, that's like low-hanging fruit. $5 and a hacksaw -- and you're delivering a ton of cheap light to the plant.

I really believe distributing the watts around the plant creates a significant efficiency (compared to top-down, single-point lighting). That was one thing I found demotivating about the way grow-lights adopted COB LED technology. I'd rather have a large fixture with 100 3w diodes than a single fisheye. (I'd rather have two fixtures with 50 3w diodes, etc.).

I actually had the idea (but never the motivation to try this): insert LED strip lighting *into* the canopy! Light it from within. Keep inserting 2w strips as the plant grows. The idea being to feed each leaf directly.

That's probably taking a good idea (distributing watts around the plant for better coverage) to an extreme. But, there are low-watt "corncob" bulbs made with SMD5630. Those are fairly efficient diodes @ 110L/w. (They were 3-4 years ago, the last time I looked into this topic.). I've always wondered how inserting some of those into the canopy might help. They're not powerful enough to burn/bleach. Everything I've seen (surrounding a plant with light) makes me think that could be a real winner. Instead of surrounding the plant with watts, insert a few within it!

But, it would be nice to have *definitive* knowledge of which household LED lightbulb has the best spectrum (best PAR output).

I got out of this topic 3-4 years ago. The lights definitely produce. I got dense buds, and the smoke was potent. I don't know many people who would complain. But, it lacked something compare to T5HO and CMH. Something about the UV, I think. I planned to buy a PAR meter and continue adding data to those documents I linked to. In fact, I was liking the lightbulbs better than the typical LED grow-light fixtures because it seemed less "secret sauce."

A lot of the grow-light fixtures are hyped. They could be better than others. But, you never know for sure. Instead of hundreds of dollars for a proprietary "trust me" fixture, $5 for a lightbulb. It seemed very counter-culture (compared to what everyone was doing). You have your kelvin color temperature available to you. You have distributed watts around the plant (a far greater efficiency than any secret-sauce spectrum). It's like the opposite of what people are doing. Simple, cheap, locally available at any hardware store. No man behind the curtain.

I still recommend it to new growers. It's definitely cost-efficient for sidelighting/supplementing "real" fixtures.

Do you have the same Philips LED & GE Brightstik lightbulbs where you're at? I'd really like to know if one has a better spectrum than the other (i.e., PAR/w). That's the one unknown ("trust me") about this. I've seen them grow very well at 20w/sq ft. I assume the spectrum must be good. But, it's still an unknown.

PS: I'm going to have the flexible/spider fixture "how-to" put up in the next day or two. That will be the last of the blogs I had (my accumulated thoughts back when I was doing this stuff.). Check the folder for that later. You're welcome to use any of that.
PAR/watt, Do you mean PPFD/watt or PPF/watt (PPE)?
I am pretty sure that most standard bulbs made for human lighting have very similar spectrum. The majority might even use the same diodes.
What I've found that differs slightly, is the number of diodes per watt that a bulb is fitted with.

If you have links to any of the bulbs you are interested in having tested, I could see if it is practical for me to buy/order and test them :)

Btw, I did find this strip build/intra canopy, if you want some inspiration. It is quite impressive :)

That also looks nice and easy(and on topic) but I think,like you mentioned ,that it can be positioned way lower judging by the plants stretch.....But its cool:)https://www.thcfarmer.com/threads/super-cheap-led-veg-light.93296/
It looked impressive as well, yes :)
To be able to compare it with something at all and have some parameter that dictates what height it should be hung at, I took a peak over at HLG.
Their HLG 65 V2 produces 290 PPFD center spot at 18" (65w) And that Is a technology that stays pretty cool and is good at keeping a high efficacy.
Comparing with 72w generic inefficient bulbs that also get very hot because of bad thermal management, you probably need to stay pretty close to achieve a good intensity for a cannabis plant at that size. Intensity can be tricky to master :) Especially by eyeballing. He made an impressive build nonetheless.
 
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PAR/watt, Do you mean PPFD/watt or PPF/watt (PPE)?
I believe PPFD (the amount of umoles falling on a surface) is the equivalent of lux (the amount of visible lightto the human eye, or lumens, falling on a surface ).

Wherase PPF is umoles emitted in all directions (total umoles, regardless of whether it lands where you want it to), the equivalent of lumens (light visible to the human eye, generated by a source in all directions). Both require a specialized integrating sphere to measure every bit of light?

Do you have the ability to measure PPF? Even if you could, it wouldn't be too meaningful because growers are more interested in light reaching a plant?

If you have links to any of the bulbs you are interested in having tested, I could see if it is practical for me to buy/order and test them
I'd have to look into this further. It appeas Cree & Philips changed their bulbs from what I was using before. Cree looks not so good right now (L/w). But, maybe Cree has a better spectrum. The basic Philips bulbs don't look as good either. The "Warm Glow" (dimming) looks similar (L/w) to what I've been using (bulbs purchased a few years ago). Phlilips has a "pro" line which looks like what they used to sell to consumers (higher L/w).

The only bulb which looks like it's remained the same is the GE Brightstik. That's the one which seemed the most directional (after removing the plastic diffusion dome). A reflector didn't help it much.

It would be useful to know which bulbs are the "best" (L/w or PPFD/w). But, I suspect that wouldn't apply globally. Different areas of the world have different brands, product lines.

Do you have any thoughts on the best PAR meter? Maybe I'll buy one. It would be easier for me to test local bulbs than for you to order them. It sounds like one of those activities that would have to be continually done because manufacturers change their products so often. A "best lightbulb of the year" sort of thing.
 
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I believe PPFD (the amount of umoles falling on a surface) is the equivalent of lux (the amount of visible lightto the human eye, or lumens, falling on a surface ).

Wherase PPF is umoles emitted in all directions (total umoles, regardless of whether it lands where you want it to), the equivalent of lumens (light visible to the human eye, generated by a source in all directions). Both require a specialized integrating sphere to measure every bit of light?

Do you have the ability to measure PPF? Even if you could, it wouldn't be too meaningful because growers are more interested in light reaching a plant?



I'd have to look into this further. It appeas Cree & Philips changed their bulbs from what I was using before. Cree looks not so good right now (L/w). But, maybe Cree has a better spectrum. The basic Philips bulbs don't look as good either. The "Warm Glow" (dimming) looks similar (L/w) to what I've been using (bulbs purchased a few years ago). Phlilips has a "pro" line which looks like what they used to sell to consumers (higher L/w).

The only bulb which looks like it's remained the same is the GE Brightstik. That's the one which seemed the most directional (after removing the plastic diffusion dome). A reflector didn't help it much.

It would be useful to know which bulbs are the "best" (L/w or PPFD/w). But, I suspect that wouldn't apply globally. Different areas of the world have different brands, product lines.

Do you have any thoughts on the best PAR meter? Maybe I'll buy one. It would be easier for me to test local bulbs than for you to order them. It sounds like one of those activities that would have to be continually done because manufacturers change their products so often. A "best lightbulb of the year" sort of thing.
Aah, I see. Yes, what is most practical is to see the PPFD/watt, IMO.
The PPF makes it very easy to see the real efficacy of the bulb. I first thought that was what you were interested in.

I use the Apogee MQ-500 when I test, both for household bulbs and our own grow lights. If you can get your hands on one, I'm sure you'd like it very much :) I use mine every day for even the smallest tasks, testing everything I see to get a natural feel for how different light sources work, what intensity they create and if it could theoretically be used to grow anything, lol. That makes it a lot easier to help everyone on different forums and social media to accurately tune in their distance, etc.

I do have the possibility to test PPF from time to time. I am not really able to do it where I am now and when I am, household bulbs are not my priority to run in the sphere :)
 
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I use the Apogee MQ-500 when I test, both for household bulbs and our own grow lights.
I just ordered one.

What do you think the best way is to represent measurements of a lightbulb? Below are my thoughts:

1. Space measured:
I chose a 2x2' (60x60cm) square because I thought that would depict a typical desired space of illumination (a plant's profile; side-lighting, or top-down).

lux-chart.png

I average the 9 inside measurements separately from the 8 outside measurements. I think that helps visualize how focused or diffuse the light is.

I then average the two averages for an overall metric (for easier comparison of one lightbulb to another). I don't know if that's the right way to do it. If I average all 17 numbers, I get a higher number than averaging two averages. (I did it this way because it was easier using a calculator. But, I should have used a spreadsheet. Averaging all 17 numbers would be easy.).

I never showed the grid (individual measurements). But, maybe that would be useful. The corners suggests what a 3x3 (90x90cm) box might look like. The diagonal length is 33.94" (86.2cm). A person could average those four corners, and have an idea what a 3x3 square would be like. (That could be informative to know how much light is falling falling onto adjacent plants. In terms of overall light perfomance, that unmeasured "outside the box" info could help. ).

Many grow-light fixtures are measured like that (but 4x4', 120x120cm). I think that's overkill or a lightbulb. Maybe even 2' is overkill. I suppose the bulb could be measured closer to the surface, and just a 12" (30x30cm) box measured. That info could be extrapolated into a 24" box (using greater distance).

2. Distance to measurement:
I measured 18" distance. But, I wasn't very confident how I did this.

2.1. If the lightbulb's globe was affixed, I measured 18" (45.7 cm) to that.​
2.2. If the globe was removed: I measured 18" to the surface of the LEDs.​
2.3. If mounted in a reflector: I measured 18" to the rim of the reflector.​

I'm not sure about that last one. Maybe globed or globeless in a reflector should have been measured the same distance as without a reflector. The numbers would have been higher that way. But, it seems like the reflector could be considered part of the lightbulb (the same way the globe is). For example, a PAR38 spot/flood would be measured to the surface of the glass (which is also the rim of the reflector).

In some ways this seems overkill for a household lightbulb. But, if I measure a few, it would be nice to have a meaningful and consistent reference. If you think it should be done differently, tell me what you think.
 
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I just ordered one.
Awesome!

I've experimented some with square PPFD-maps. At first, I tried to cut corners and only measure at 41 points, but I quickly realized that the result was insufficient and the numbers ended up feeling too far apart to be able to grasp how far the footprint actually stretched with a certain intensity threshold. I quickly realized I had to re-invent and ended up with 9x9 measuring points instead. Obviously, it is very different to measure big square-shape lamps compared to small round household bulbs.
PPFDtemplate.jpg

When I made the video that this thread started with, I wanted to make lines that were visually easier to understand and that represented a certain intensity.
This is the first time I experimented with this type of PPFD-map and first I started to literally measure every inch and carefully draw right under where the sensor stood. One complete circle ended up in over 20 measurements. Once the map was complete, I figured out that the circles were very round and nicely shaped, in other words, this type of bulbs does produce an intensity that in turn produces very nice and evenly shaped rings. I stopped measuring 20+ times per circle and started measuring out from the most intense spot instead, only taking one measurement per line and then using a string to draw half circles. I did this on top of 1'x1' drawn squares just to have some base for it all and being able to compare the different bulbs to each other.
9wLED.png

Personally, I think it is easier to see and understand how the intensity stretches. One nice example is the two 9,5w LED, one with diffuser dome, and one without.
Displaying it in numbers and measuring it at certain spots would create a completely different picture. I find it pretty interesting that the 25PPFD lines are almost still exact while the centre spot differs so much. Although, It gets more difficult to compare them and calculate differing percentages from drawn circles. I guess it depends a little bit on who you are going to show the results to. If it is someone very familiar with PPFD and grow lights or someone that has never even thought that light intensity can be measured. And btw, I measured from the rim in both cases, where the LEDs are mounted.

Let me know what you think :)
 
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Let me know what you think
When I did the 17-measurement 2x2' grid, I noticed it usually wasn't uniform. The north side might have stronger readings than the south. (Maybe the socket wasn't hanging perfectly straight. I should slip an iron pipe over the cord, let it rest on the top of the socket housing. Maybe it would plumb itself better.).

I feel like all sides should be measured. If just one side, and if a diode were mounted with a minuscule angle (or, the socket isn't perfectly plumb, or socket's threads are a little wobbly), then it's random if the good (or bad) side is being reported.

I like the idea of keeping it simple. My 17 measurements seemed like overkill for a household bulb. But, the risk is missing a spot that might reflect better on the bulb.

I'm thinking measuring the bulb *closer* to the surface would be better. Like your 6" distance. That's comparable to the distance I mount 9-10 (60w-equiv) bulbs from the leaves. A 15-16w (100w-equiv) might be 8-10". (I didn't use those very much. I liked to use lower-watt lightbulbs -- but more of them, spreading the light over the plant, better/even coverage). A 19-20w PAR38 floodlight would be 12-16".

So, my 18" distance is probably too much. I the light were more concentrated, the 24" corners wouldn't be as meaningful. You're 6" distance has me thinking about measuring a 6" box inside a 12" box (17 measurements again, but a smaller footprint with fewer irregularities between measurements. The light should be more uniform if it's tighter together/focused.).

One thing that concerns me about being too close: hitting the exact measurement points could be tedious. Being just 1/8" off could alter the value (whereas, when the lamp is 18" above, 1/8" lateral movement wouldn't be as great (relatively speaking).

I'll have to play with it. I'm imagining how it would work. I won't know until I try.

EDIT: I like the idea of measuring to the LEDs regardless of globe, reflector. PAR38 floods/spots may have suspended LEDs (mounted on a post). That might complicate things.
 
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How much are you guys spending setting up these lights? Just seems like it may be close to what it would cost to build a cob light, which is more efficient and puts out less heat.
 
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How much are you guys spending setting up these lights? Just seems like it may be close to what it would cost to build a cob light, which is more efficient and puts out less heat.
That's a good point. I have a complicated answer. First, I'm not growing under these lightbulbs anymore. But, they do grow. And, I still use them for supplemental side-lighting in flower. So, the investment in mounting equipment is long-term.

In that sense, I think these lightbulbs are great for new growers. A new grower faces a lot of lighting choices -- before they even know whether the can grow! So, these clamp-on reflectors and household lightbulbs are a decent way for such person to see if they can grow (without making a large investment in lighting, or buying a cheap and flim-flam LED fixture). If/when they discover they can grow, they can buy a "real" grow light and use the lightbulbs as supplemental lighting. (More tools in the toolchest.).

The other nice thing is that many people can't build. Me & the OP might not hesitate to build low-watt COB fixtures and get better surround-light than household LED bulbs. But, most people aren't going to delve into that world of "what's the latest and greatest." The nice thing about household LED lightbulbs is that anyone can run down to Home Depot and be done with it. (They need a hacksaw too.).

And, I'm not convinced COBS are better, either. I had really good results from 18-22w/sq ft of household LED lightbulbs surrounding a plant. I haven't looked at COB for 3-4 years. Maybe it's improved. But, breaking the 20w/sq ft barrier is about as good as it gets, I think. (I linked to photos of that grow earlier in my first reply to the OP).

[In fairness: I haven't looked at household LED lightbulbs during that period either. (I think LED lacks UV. I prefer T5HO @40w/sq ft for short spaces, CMH @35w/sq ft for tall spaces.). Revisiting that topic recently, I see Cree & Philips have replaced their lightbulbs with what appear to be lower-performing bulbs. So, maybe it's not as attractive as it was. I'm looking forward to measuring PPFD soon. I'll buy new bulbs and baseline things again (compare the bulbs from 3-4 years ago).]

Your comment implies COBS are "better." But, define better? For some (many?) people, driving 3 miles to the hardware store for lighting could be better. Having off-the-shelf lighting, replaceable bulbs could be better (leveraging standardized/commoditized mounting hardware). It's just a different emphasis on what's better?
 

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