# LED lights and PAR w/ Paphs&Phrags



## shade131 (Feb 7, 2019)

I know this won't apply to a lot of people who use good ole sunlight....

I tried searching this site but the search functions rejects "LED lights PAR" and most variations thereof. So apologies if this info is already on the site - I tried. 

I use LED's exclusively for now. I think they're generally fantastic technology. What scant information is out there online about growing orchids under LED lights (99% is, of course, about growing weed) suggests that the ideal PAR is around 100 (umoles m-2 s-1) for paphs. I was a little stunned by this, as I estimate mine are getting from 150-400 at 20-24" under a 450w grow light. Huge range, I know. It's a very rough estimate, and I finally bit the bullet and ordered a PAR meter. 

Anyway, if anyone out there is using LED's and would like to compare notes, as far as I can tell there is very little hard data aside from one study on P. insigne. So any information or experience would be very valuable to me. 

One vexing development I'll throw out there:

The following species/hybrids burned to varying degrees: callosum, Gloria Naugle, delenatii (v.dunkle), Ho Chi Minh, Deperle and Phrag. Eric Young...Notably, culturally similar ones right next them - other parvi, brachy and multis - did not. 

I can't make any sense of the Gloria Naugle or the Phrag burning when other supposedly lower light paths didn't burn. Maybe I pulled them out of the shipping box and into the light too quickly and it shocked them? Just a weird individual? Otherwise, many of the others have some delenatii in them, so l guess delenatii might be more sensitive than others with PAR? 

So, like I said, any and all people out there using LED's, your experiences and expertise would be greatly appreciated!

Brandon


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## Duck Slipper (Feb 7, 2019)

I agree Brandon, I also did a search and didn't get much info on LED's. I think it is just a new form of gro light and many people are already successful using T5, T12, MH, HPS. I recently purchased 2- 6 bulb T5's. But, I made that purchase because I already was successfully using T12's and considered the T5's an improvement. I just couldn't read enough about LED's, to purchase them. Not to mention the variations of LED available and which to purchase. Dan


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## terryros (Feb 8, 2019)

I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.


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## shade131 (Feb 8, 2019)

Duck Slipper said:


> I agree Brandon, I also did a search and didn't get much info on LED's. I think it is just a new form of gro light and many people are already successful using T5, T12, MH, HPS. I recently purchased 2- 6 bulb T5's. But, I made that purchase because I already was successfully using T12's and considered the T5's an improvement. I just couldn't read enough about LED's, to purchase them. Not to mention the variations of LED available and which to purchase. Dan



Duck - thanks for the thoughts. I hear you. The technical specs get mind-numbing pretty quick with LED. One significant advantage of fluorescent tubes is they lend themselves to stacking much more than your run of the mill hanging LED rectangle. If I had it to do over I might’ve gone with a series of long strips of LED so I could keep the intensity down at close range and still keep the lights relatively close to plants. And grow more plants in the same vertical space....On the other hand, having lights far away from plants makes tall spikes much easier to deal with.


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## shade131 (Feb 8, 2019)

terryros said:


> I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.
> 
> 
> Sent from my iPad using Tapatalk Pro





terryros said:


> I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.
> 
> Terry - that’s helpful, thanks! I’m definitely running my phrags too bright it seems. Burned leaves are the worst, just ruins the appearance of my otherwise healthy blooming phrags. ....I’ve come across similar information for beam angle. It’s still very much uncharted territory, especially regarding orchids. What’s exciting to me is that - theoretically - the ability to customize wavelength, intensity, and duration should ultimately give LED an advantage over any type of artificial lighting, and even sunlight. Long ways away, but a lot of the agricultural research using vertical LED farms for produce is very encouraging. Great yields, very low cost of production since LED use little electricity, water, fert and humidity can all be controlled precisely, etc....but I digress
> 
> ...


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## xiphius (Feb 8, 2019)

Another consideration with the LED vs tubes is intensity for area of coverage. A lot of the dedicated LED grow lights out there are small and boxy. This creates a relatively high-intensity light that covers a small area. Tubes that are 4ft long cover a larger area at lower intensity. The bulk of my orchids are in a grow tent under a 300W LED light that 3-4 ft from the plants and I feel like it is on the cusp of being *too* intense for plants directly underneath it. The ones on that side of the tent tend to run a bit more yellowish green than I would like (but still grow well). At some point I will probably replace it.

In that respect, those types of LED lights aren't great for a large-ish collection unless you can mount them really high over the plants since they don't cover a very large area relative to tubes (and are much more expensive).

That said, I really like LEDs and feel they are future of growing under lights. I have been really happy with how they have grown my orchids.

I haven't taken measurements myself (don't have a meter), but the light I have is rated around ~100 umol/m^2/s at around 36 in distance (remember that PAR ratings are going to be highly distance dependent... closer obviously = higher).


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## terryros (Feb 8, 2019)

I have always used ALT LED lights that I obtain from Orchids Limited in Minnesota. These bulbs screw in to track lighting fixtures. My 40 degree angle bulbs are 7 watt MR16 bulbs and my 60 degree bulbs are either 15 watt or 20 watt bulbs. All of these bulbs have superior heat dissipation design. I can easily touch and untwist the bulbs when they have been turned on for hours. The key part of this is that bloom spikes can be fairly near to these bulbs without damage. I can have the MR16 40 degree bulbs at least 2 feet above the leaf tops with Phals and Phrags which accommodates the great majority of spikes. The 60 degree bulbs can be at least 6-8 inches above Cattleya leaf tops so accommodate most spikes.

Yes, these bulbs are more expensive than many you can find, but I think I am getting what I am paying for - the beam angle, the heat dissipation, the consistency. I have had very few failures in the bulbs and they maintain their illumination for years.


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## gego (Feb 8, 2019)

I measured mine in foot candles and use 900 to 1200 FC for flowering sizes, 400-800 for seedlings depending in size.
I noticed an adjustment period if they came from natural light. So newly moved plants will get lower intensity first until new leaves come out. If I don't do that, leaves will turn yellowish even though they had the same FC from natural light.
I noticed the new leaves coming out are darker green, like they adjusted to the new source and started to grow again.
And maybe because the intensity is constant unlike natural light, older leaves started to turn yellowish on the matured plants. I increased my fert strength and the yellowing stopped and some of them started to turn green again.
Dont know if the measurements from natural and LED is apple to apple. I just use them for reference and just observe the plants then adjust accordingly.
One thing for sure,,,,when using LED for the first time,,,, start from a low intensity,,, meaning more distance to the leaves then lower the source gradually.

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## Ray (Feb 9, 2019)

gego said:


> I noticed an adjustment period if they came from natural light. So newly moved plants will get lower intensity first until new leaves come out. If I don't do that, leaves will turn yellowish even though they had the same FC from natural light.



I don't know if It applies in your situation, but many folks don't realize that they are giving their plants way too much light under any artificial source when compared to natural lighting.

The progression of natural light from dawn to noon to dusk provides half the volume of photons to the plant than does artificial light at that same peak intensity (which is what most culture sheets provide) kept on for the same duration.


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## gego (Feb 9, 2019)

Ray said:


> I don't know if It applies in your situation, but many folks don't realize that they are giving their plants way too much light under any artificial source when compared to natural lighting.
> 
> The progression of natural light from dawn to noon to dusk provides half the volume of photons to the plant than does artificial light at that same peak intensity (which is what most culture sheets provide) kept on for the same duration.


Agree. And that should be taken into considerations. Also it has a different source of wavelengths but i noticed they adjust as they grow. Some LED,,, expensive ones provide the broad spectrum,,,I think it is worth it. They keep for a long time
I actually have multiple bulbs arranged about 45 degrees from the plants on booth sides. Then I use timers to mimic morning, noon and afternoon. Spikes can go up unrestricted.

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## shade131 (Feb 9, 2019)

Really appreciate all the information. Over the last few days I’ve slowly been coming to the realization that I have way more lighting than I need. I’ll be able to get hard data when my PAR meter shows up, but I’m pretty confident that I’m growing paphs under dendrobium or cattleya light levels. I’m going to have to completely overhaul my setup to be able to hang the lights higher. What’s interesting is that while I noted that several burned (largely delenatii or its hybrids - I thought parvis would be less likely to burn?) 80% are doing really well. Maybe a few here or there that are a bit bleached out, but many have spiked. Watering a good bit, Humidity 50-70%, temp 55-70, and a ton of airflow. Maybe all that adds up to them tolerating more light than normal. I’ll post some pictures later. Have a good weekend everyone.


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## shade131 (Feb 9, 2019)

gego said:


> Agree. And that should be taken into considerations. Also it has a different source of wavelengths but i noticed they adjust as they grow. Some LED,,, expensive ones provide the broad spectrum,,,I think it is worth it. They keep for a long time
> I actually have multiple bulbs arranged about 45 degrees from the plants on booth sides. Then I use timers to mimic morning, noon and afternoon. Spikes can go up unrestricted.
> 
> Sent from my SM-G955U using Tapatalk



This sounds like a great idea. Solves the spike dilemna and encourages symmetrical growth.


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## gego (Feb 9, 2019)

shade131 said:


> Really appreciate all the information. Over the last few days I&rsquo;ve slowly been coming to the realization that I have way more lighting than I need. I&rsquo;ll be able to get hard data when my PAR meter shows up, but I&rsquo;m pretty confident that I&rsquo;m growing paphs under dendrobium or cattleya light levels. I&rsquo;m going to have to completely overhaul my setup to be able to hang the lights higher. What&rsquo;s interesting is that while I noted that several burned (largely delenatii or its hybrids - I thought parvis would be less likely to burn?) 80% are doing really well. Maybe a few here or there that are a bit bleached out, but many have spiked. Watering a good bit, Humidity 50-70%, temp 55-70, and a ton of airflow. Maybe all that adds up to them tolerating more light than normal. I&rsquo;ll post some pictures later. Have a good weekend everyone.


There is a Lux light meter app,,, it is free. It works well. May not be very precise but it gives you a good reference and the reading is consistent. That is all that matters.

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## masaccio (Feb 12, 2019)

*Overlighting?*

Hm. This is on the heels of having just read Ray's comment above that many of us don't realize we're over-lighting with artificial light. I have a long window ledge that I've fitted with a line of LED spotlights. They're not special grow LEDs, just Sylvania home-use spotlights that were recommended by a trusted source for orchids. They're rated at 25 watts, 250 watt equivalent. 2650 Lumens. I don't really speak "lumen" but maybe some of you do. (Growth flowering and rooting all good, for the most part.) I worry if my par meter goes under 300 umols for anything. For most plants its between 400 and 500 or higher. I'm beginning to think that I'm grossly overlighting my orchids based on what I'm reading here. I have various paphs (a couple of brachys, a warm multifloral and a complex hybrid, also phals, a cattleya seedling. I have noticed some tendency of "purple-izing" and a little paling. Maybe its time to pull them up. (Ya think?) Also maybe will run them 12 hours a day instead of 14? It sounds like I should be going for between 100-300 umols ? I think my LED skepticism maybe got the better part of my judgment. The pic represents the setup except there are eight lights now instead of five. I did this to get more even coverage between fixtures. But if I raise them up, the coverage could even out and I could do with fewer fixtures as well.


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## gego (Feb 12, 2019)

Gaging from the distance and the wattage of the bulb,,, you are definitely overdoing it. The intensity and the duration will add up.
I good gage is a Lux meter I stated above, you can down load the app for free. Set the units as Foot-Candles. With your phone, you can gage how much light your plant is receiving. For big multi,, 900-1100 FC is a good number. Since these bulbs have lenses, the constant intensity of the light striking the same spot on the leaf can actually make a burn. So blowing air is needed. I would not be surprised if those leaves are subjected to 2000-3000 FC measured using the app. 
Goodluck

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## Ray (Feb 12, 2019)

If this is a repetition of formerly posted info, I apologize.

Another LED "Oops" is replacing fluorescents with LEDs having the same output and having them at the same distance from the plants.

A fluorescent tube radiates in all directions, and no matter how good the reflector, much less than 100% of the light reaches the plants. With many LEDs, a much greater percentage is radiated toward them, with spot and flood lights approaching 100%.


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## masaccio (Feb 12, 2019)

gego said:


> Gaging from the distance and the wattage of the bulb,,, you are definitely overdoing it. The intensity and the duration will add up.
> I good gage is a Lux meter I stated above, you can down load the app for free. Set the units as Foot-Candles. With your phone, you can gage how much light your plant is receiving. For big multi,, 900-1100 FC is a good number. Since these bulbs have lenses, the constant intensity of the light striking the same spot on the leaf can actually make a burn. So blowing air is needed. I would not be surprised if those leaves are subjected to 2000-3000 FC measured using the app.
> Goodluck
> 
> Sent from my SM-G955U using Tapatalk



Really? I'm not knowledgeable about paphs, but I thought those roth-type multiflorals liked cattleya-level light. Maybe you were speaking of another type of multi? Or maybe my info is outdated. OR, (maybe I'm getting this) the number is lower because, as Ray pointed out, they're getting that consistent level of FC for several hours all day, every day. Yes?


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## gego (Feb 12, 2019)

Yes. Even catts will burn if the angle is just right. Anyways, it is better to not guess by measuring. That's just my opinion since you showed us your set up. I did not mean you dont know your plants.
Good luck.

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## shade131 (Feb 13, 2019)

So I got I my PAR meter and I can confirm that they were all getting a minimum of 220, all the way up to 400. Unfortunately, I could only raise the lights a few inches, but that got it down to 140-300. Given that the majority were doing well under very high light, I *think* I should be fine now. I think good airflow and humidity can raise their threshold. I’d also speculate that the tiny bit of info out there claiming that you should never go above 150-200 for ANY Paph is misguided. 

If any of you growing under LED have similar concerns, Amazon has a PAR meter for $100usd that justified its price after about 30 seconds of use. Very handy.


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## Ray (Feb 13, 2019)

shade131 said:


> If any of you growing under LED have similar concerns, Amazon has a PAR meter for $100usd that justified its price after about 30 seconds of use. Very handy.



Which one did you get?


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## shade131 (Feb 13, 2019)

This one. Hydrofarm is the brand. It was actually $120. Still a lot less expensive than all the others. 

https://www.amazon.com/Hydrofarm-LG...rds=par+meter&qid=1550106073&s=gateway&sr=8-6


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## Ray (Feb 14, 2019)

I purchased one of them a while back. POS failed in a short time... I hope you have better luck with yours.


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## southernbelle (Feb 18, 2019)

terryros said:


> I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.
> 
> 
> Sent from my iPad using Tapatalk Pro


Thanks, Terry. I encourage you to publish your growing experience with LEDs as info re growing orchids under them is non-existent, as you know. If not totally complete, you could do an update in a year or so...


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## southernbelle (Feb 18, 2019)

shade131 said:


> This one. Hydrofarm is the brand. It was actually $120. Still a lot less expensive than all the others.
> 
> https://www.amazon.com/dp/B0055F59LA/?tag=skimlinks_replacement-20


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## southernbelle (Feb 18, 2019)

I purchased the LED tube lights (like fluorescents) from Jerry Fischer, Orchids Ltd. They will custom make the fixture with the number of tubes you want. Big advantage is low wattage (45 watts per bulb) 5,000k (daylight) and very little heat generated (less than 5 degrees rise in room when lights come on). I use one tube for phals, paphs and phrags. I vary the PAR by height above canopy, but my lights are about 24” above canopy so very comfortable headroom. I use same PAR as terryros stated. I use 3 tubes for catts, again vary height of fixture for lower vs higher light types. I forgot to mention my lights are 60 degree. They come in 60 and 120, I believe. Also, when I moved my catts from windowsill (where they had never bloomed for 3 years) to under lights, they spiked within 3 weeks. Very rewarding! I would recommend giving a little less light at first, so plants can adjust. I went straight to my full PAR settings and got a little burning on some of the lower light catts. Not major, but could have been avoided. Also, if using Foot Candles, because of the constant light intensity throughout the time lights are on, you will use about 1/2 of what is recommended (which reflects light at noon on sunny day in nature); i.e. 1500 FC for phals would equal about 750 FC under lights, or 50-75 PAR. By the way, I learned all of this from people who have gone before me in this and were extremely helpful.


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## TyroneGenade (Feb 18, 2019)

Hello,

I am getting in here late in the games but think I still have some useful info to offer.

Gego is right, you can get lux meter apps for your phone and these can be very helpful if you know something about the LEDs you are working with. 

See https://www.waveformlighting.com/horticulture/convert-lux-to-ppfd-online-calculator for how to convert from Lux to PPFD.

For instance, I got some of these: https://www.amazon.com/dp/B07GWB1JZY/?tag=skimlinks_replacement-20 . About 10 inches from one of the lamp I measured 2900 lux with a cell phone. These are high CRI (color rendering index) lamps so I selected "high CRI LED 6500K" off the drop down menu, entered 2900 lux and clicked calculate and got 49.98 PPFD. Not too shabby...

Working with grow lights is more of a pain as the exact ratio of blue to red LEDs is needed to calculate PPFD from lux. This can be done with pen and pencil, linear programming blah blah mathematics blah blah blah... If your grow light is 1:1 red:blue then you can just use the 2nd last option from the drop-down menu.

Bye


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## xiphius (Feb 18, 2019)

TyroneGenade said:


> See https://www.waveformlighting.com/horticulture/convert-lux-to-ppfd-online-calculator for how to convert from Lux to PPFD.



Interesting link with the calculator. However, I find it curious that they don't include a distance factor in their calculation (remember that PAR measurement is highly dependent on distance from the light). I wonder what the default is that the calculator uses (unless it is giving measurements at the light?). The text doesn't seem to say/specify. Generally when you see a manufacturer report PAR values it is accompanied by a reference distance or as a table of values at different reference distances. As far as I am concerned, a PAR value _without_ a reference distance is a pretty useless measurement that doesn't really tell you anything...


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## Ray (Feb 18, 2019)

xiphius said:


> As far as I am concerned, a PAR value with a reference distance is a pretty useless measurement that doesn't really tell you anything...


I'm not sure if I'm agreeing or disagreeing!

The photosynthetic photon flux density (PPFD) - µmol/square meter/second - should be read at the plant, not at the source, but that can be said for all light sources, can't it?

Foot-candles and lux - AND PPF, for that matter - only tell you the light intensity, the first two being the brightness to the eye, the third being the actual photon flow rate. They, in my opinion, are of little value for any lamp, unless you already have some experience with them. The physical configuration of the emitting light source has a huge impact on the PPFD at the plant. For example, a linear fluorescent tube, spiral compact fluorescent lamp, and chip-on-board LED having the exact same PPF will have entirely different flux densities at the same distance.

The tube radiates in 360 degrees down its entire length, making it a somewhat cylindrical emitter. A large percentage has to be reflected (so the reflector is part of the equation, as well) toward the plants and some is lost altogether, as it reflects right back to the lamp. Plus, the total output is spread out down the length of the tube. The spiral CFL also radiates in all directions, but more spherical than cylindrical, plus a significant percentage of the emitted energy is trapped inside the spiral. That COB LED, on the other hand, puts out all of its energy from a small area, and it is projected over a bit more than 180° without any reflector, in more of a hemisphere.

What there really needs to exist for ALL lamps is a series of "stacked maps" of flux density. Each "stack" would be a different distance, and each "map" would be for a fixed distance from the central emitting axis of the lamp, and would show the PPFD at the center, and multiple places around it - sort-of like this:


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## xiphius (Feb 18, 2019)

Ray said:


> I'm not sure if I'm agreeing or disagreeing!
> 
> The photosynthetic photon flux density (PPFD) - µmol/square meter/second - should be read at the plant, not at the source, but that can be said for all light sources, can't it?
> 
> ...



Well put Ray. I think you are more elegantly expounding what I was kinda trying to get at above. However, I stand by my assertion that PAR readings without a reference distance are pretty useless. Lumen/lux ratings are basically the total intensity, so it is pretty easy to understand - higher = brighter light. So even if you don't know the exact distance you will be using, it gives you some basic info about the light (bigger rooms will need brighter or more lights). But PAR values are more complicated in that they are measuring the total USABLE light for a plant (based on what plants can actually use for photosynthesis). So, it is more than just pure output. A high lumen light can have relatively low PAR ratings at whatever distance if the spectrum is all wrong and a relatively low lumen light may have decent PAR ratings if the spectrum is perfect. You are absolutely correct in that they need to be measured at the plant. If it isn't being measured at the plant (or a distance given for reference), then the value is useless because it tells you very little-to-nothing about what the plant will "see" or where you need to position a plant to get it to grow well. A PAR value of 200 umol/m2/s at the light is pretty useless if your lights are far from the plant and/or the bulb design is such that intensity drops off quickly. I absolutely agree that stacked maps of flux density are the best (basically a better/more precise version of the "PAR @ such and such a distance" tables I have seen from some manufacturers). I wish all manufacturers did that.

Also... sorry for the typo in my previous post. That should have been "a PAR value _without_ a reference distance is a pretty useless measurement that doesn't really tell you anything..."


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## masaccio (Feb 18, 2019)

shade131 said:


> So I got I my PAR meter and I can confirm that they were all getting a minimum of 220, all the way up to 400. Unfortunately, I could only raise the lights a few inches, but that got it down to 140-300. Given that the majority were doing well under very high light, I *think* I should be fine now. I think good airflow and humidity can raise their threshold. I’d also speculate that the tiny bit of info out there claiming that you should never go above 150-200 for ANY Paph is misguided. If any of you growing under LED have similar concerns, Amazon has a PAR meter for $100usd that justified its price after about 30 seconds of use. Very handy.



Shade131, "I'm struck" as to the common experiences we both are having with these lights. I had a wild thought the other day. Use my PAR meter on daylight. It was a great day to do that because the sun was going in and out of semi-cloudy conditions and I took quickly successive footcandle and PAR readings. I was shocked at the lowish PAR readings I was getting in the 2500-3000 footcandle range. And that's considered generous for paphs, right? Definitely in the 100-200 range. When the sun was more fully out but still filtered by the upper canopy of some trees, I could see some shadow (about right for catts maybe) and was getting 300ish PAR readings (which is what terryros uses for her catts in a post above). When it was full out. the readings were 600-700-800+. My first though was, why didn't I think of this before ??? (Kind've a duh moment.) But think I had to see it for myself to believe it. The footcandle readings under my lights is 4000 and some of mine were turning purple, even a seedling catt. But it was getting worse so the lights are all the way up and I'm limiting illumination to 12 hours a day. Actually considering replacing the bulbs too. I'm also curious which meter you got. I have the Hydrofarm, which I'm being very careful with, given the Amazon comments.


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## masaccio (Feb 18, 2019)

Oops, didn't get to p.2. I see you bought the Hydrofarm as well. So far mine has been fine, except it doesn't hold a battery charge. If I plug it in for a couple of minutes it's usually enough juice to take around with me for that series of measurements. But even when I charge it all the way up it doesn't seem to hold the charge even overnight. Apparently the biggest problem is the fragility of the connection of the sensor to the main unit. I'm taking great care not to stress this at all. So far so good. PS, if you want to share in a pretty good spectrometer, it would only be about $800 apiece.


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## TyroneGenade (Feb 18, 2019)

xiphius said:


> ... I find it curious that they don't include a distance factor in their calculation (remember that PAR measurement is highly dependent on distance from the light). I wonder what the default is that the calculator uses (unless it is giving measurements at the light?). The text doesn't seem to say/specify. Generally when you see a manufacturer report PAR values it is accompanied by a reference distance or as a table of values at different reference distances. As far as I am concerned, a PAR value _without_ a reference distance is a pretty useless measurement that doesn't really tell you anything...



All the calculator is doing is converting one density measure of light into another. It is taking Lux (lumens per square meter) and converting it to PPFD (microEinsteins per square meter per second). It is using the different spectra to convert from lumens (a parabolic curve heavily weighted on yellow/green) to microEinsteins (wan equal weighting of photons). In this conversion the distance from the light source is irrelevant. 

With an excellent reflector you could get the same PPFD whether you are 1 cm or 1 m away. For a point source of light you can expect the PPFD to be 25% of what it was every doubling of the distance from the light source but different geometry applies to different light sources. If you have source with a 90o beam angle then the density of photons halves with every doubling of the distance from the light source. 

I agree that manufacturers should tell us what the PPFD is a specific distance and what the beam angle is. Then we can always calculate what the PPFD would be at a particular distance. I see that many light manufacturers still don't do this... But almost all will tell you the beam angle and the lumens so you can calculate Lux and so convert to PPFD.

As a side note, PAR means Photosynthetically Active Radiation. This is not what a quantum meter gives you. A quantum meter measure microEinsteins per square meter per second (i.e. the number of photons striking the probe per second per unit area). The measure is unweighted by the typical photonic response of plants (i.e. photosynthetically active radiation). I have written on this before elsewhere: http://www.apsa.co.za/xenforo/threads/lighting-basics-for-people-new-to-the-aquascaping-hobby.11329/ .


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## southernbelle (Feb 19, 2019)

masaccio said:


> Oops, didn't get to p.2. I see you bought the Hydrofarm as well. So far mine has been fine, except it doesn't hold a battery charge. If I plug it in for a couple of minutes it's usually enough juice to take around with me for that series of measurements. But even when I charge it all the way up it doesn't seem to hold the charge even overnight. Apparently the biggest problem is the fragility of the connection of the sensor to the main unit. I'm taking great care not to stress this at all. So far so good. PS, if you want to share in a pretty good spectrometer, it would only be about $800 apiece.


I tried the Hydrofarm meter and was not getting consistent readings. Returned it. This is the PAR meter I use and have excellent consistent results measuring at top of leaf canopy. Pricey but well worth it in the long run.
https://www.apogeeinstruments.com/mq-100-quantum-integral-sensor-with-handheld-meter/


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## xiphius (Feb 19, 2019)

TyroneGenade said:


> All the calculator is doing is converting one density measure of light into another. It is taking Lux (lumens per square meter) and converting it to PPFD (microEinsteins per square meter per second). It is using the different spectra to convert from lumens (a parabolic curve heavily weighted on yellow/green) to microEinsteins (wan equal weighting of photons). In this conversion the distance from the light source is irrelevant.



Thanks for the explanation. I get that the distance in this specific conversion isn't actually an issue (however, without a given reference distance, the number still tells you basically nothing). In terms of plant lighting, distance is definitely a factor... and that PPFD measurement would only be relevant at whatever distance the initial lux measurement was made by the bulb manufacturer (which is am guessing is probably at, or very very close to, the bulb in most cases).



TyroneGenade said:


> With an excellent reflector you could get the same PPFD whether you are 1 cm or 1 m away. For a point source of light you can expect the PPFD to be 25% of what it was every doubling of the distance from the light source but different geometry applies to different light sources. If you have source with a 90o beam angle then the density of photons halves with every doubling of the distance from the light source.



This. Exactly this. Flux is distance dependent. As you move away from the source, you get a spread (dependent on the reflector and bulb design). Without knowing what distance (and possibly position) the measurements were taken at, you may as well be shooting in the dark. I think it is safe to assume that the default position would be centered under the light... but there isn't really a clear "default" distance.



TyroneGenade said:


> As a side note, PAR means Photosynthetically Active Radiation. This is not what a quantum meter gives you. A quantum meter measure microEinsteins per square meter per second (i.e. the number of photons striking the probe per second per unit area). The measure is unweighted by the typical photonic response of plants (i.e. photosynthetically active radiation). I have written on this before elsewhere: http://www.apsa.co.za/xenforo/threads/lighting-basics-for-people-new-to-the-aquascaping-hobby.11329/ .



Interesting. That is quite an extensive writeup you have there, and very informative! Good on you for that. Still a bit confusing though. I had always thought that PAR and PPFD were very similar. If PAR is the absolute quantity of photosynthetic photons produced by the light, then why do you normally see "PAR" measurements from light manufacturers reported with units of flux (literally every time I see PAR measurements, they are in umols/m2/s)? Or are most "PAR" measurements reported by manufacturers actually reporting PPFD? Thanks for clarifying!

Also, you are correct that a base quantum meter does not weight based on photosynthetic versus other photons... it just detects photons. However, I know that a lot of special-made PAR or PPFD meters are quantum meters that include filters over the sensor which do select for photosynthetic photons to an extent. So... gotta be a little careful there.


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## TyroneGenade (Feb 19, 2019)

People use PAR and PPFD interchangeable but they are not the same. This blurring of definitions makes it very difficult to have good discussions about the subject. Using the spectra of various lamps and their wattage you can calculate the PAR emitted from a lamp. If you have the beam angle, reflector efficiencies and distance from the lamp you can calculate the PPFD. Same for lumens and Lux. 

All I'm saying with the converter is that if you have a LUX value you can estimate the PPFD. This means you can load a luxmeter app on your phone and save yourself 100s of dollars on a good quantum meter (e.g. Apogee). 

The aquatic plant scheme is quite crazy about PAR, PPFD readings... but the data tells us that CO2 is more important before light quantity and quality. What I find so interesting about this thread is the same observation that 100 PPFD is about as much as the Orchids can take before there are problems. From about 40--70 PPFD aquatic plants are already severely CO2 limited and extra light won't help you grow the plants any better. The situation is completely different for crop plants that don't seem to get saturated with light until well over 1000 PPFD. So this is very interesting...


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## xiphius (Feb 19, 2019)

TyroneGenade said:


> People use PAR and PPFD interchangeable but they are not the same. This blurring of definitions makes it very difficult to have good discussions about the subject. Using the spectra of various lamps and their wattage you can calculate the PAR emitted from a lamp. If you have the beam angle, reflector efficiencies and distance from the lamp you can calculate the PPFD. Same for lumens and Lux.
> 
> All I'm saying with the converter is that if you have a LUX value you can estimate the PPFD. This means you can load a luxmeter app on your phone and save yourself 100s of dollars on a good quantum meter (e.g. Apogee).
> 
> The aquatic plant scheme is quite crazy about PAR, PPFD readings... but the data tells us that CO2 is more important before light quantity and quality. What I find so interesting about this thread is the same observation that 100 PPFD is about as much as the Orchids can take before there are problems. From about 40--70 PPFD aquatic plants are already severely CO2 limited and extra light won't help you grow the plants any better. The situation is completely different for crop plants that don't seem to get saturated with light until well over 1000 PPFD. So this is very interesting...



Fair enough. Thanks for all the useful info on PAR vs PPFD. I feel like I understand both a lot better now!

I feel like aquarium plants versus plants exposed to air are a completely different ball game. Crop plants have direct access to atmospheric CO2 (roughly 0.04% of "air"). For crop plants, the atmosphere is a bulk reservoir and it is reasonable to assume that the CO2 concentration remains roughly constant over time. Aquarium plants have to compete for what little CO2 there is dissolved in the "box" and once it is used up, have to wait for more to dissolve in from the air or through fish respiration (both slow processes - especially dissolving from the atmosphere because of low surface area and minimal surface agitation). This is exacerbated in a small aquarium where the plant-to-water ratio is pretty high since the volume of water is a LOT less than what you would find in a lake/stream (which could also be considered to have a roughly constant concentration since the plant-to-water ratio is very very low). So, I am not surprised that CO2 is a lot more limiting than light here.

Btw... your tank picture in that link is gorgeous. I also have a couple planted tanks .


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## TyroneGenade (Feb 22, 2019)

xiphius said:


> Btw... your tank picture in that link is gorgeous. I also have a couple planted tanks .



Thanks, but with one more tube and some CO2 it looked even better:


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## masaccio (Feb 22, 2019)

Stunning!


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## shade131 (Feb 23, 2019)

Very cool. I was unaware of how amazing aquaculture can be until recently. If any of you haven’t seen the photos, it’s worth a google.


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## Ray (Feb 23, 2019)

Another look at the units:

PAR (Photosynthetically Active Radiation) - Those wavelengths between 400 & 700 nm. There is no information on the actual spectrum or the amount of light being projected.

PPF (Photosynthetic Photon Flux) - How much light (number of photons) is leaving the source per unit time. It is a constant (ignoring lamp degradation).

PPFD (Photosynthetic Photon Flux Density) tells us the number of photons per unit time hitting a unit of area. Because photons spread out as they leave a light source, this is dependent on distance from the lamp, and is closest to lumens or lux, albeit plant-centric rather than human eye-centric. 

(Theoretically, if all of the photons were collimated, with no losses to the sides, the PPFD would be independent of distance - think of a lamp made up of an assortment of lasers having PAR wavelengths, all pointing at your plant, or 100% of the output of a LED panel "piped" to your plants through optical waveguides.)


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## xiphius (Feb 24, 2019)

Ray said:


> Another look at the units:
> 
> PAR (Photosynthetically Active Radiation) - Those wavelengths between 400 & 700 nm. There is no information on the actual spectrum or the amount of light being projected.
> 
> ...



Thanks Ray! Yeah, this discussion has really helped clarify some things for me. I think this brief, basic, discussion of units and metrics is sorely lacking in many of the sources that try and explain PAR/PPFD online (even the most basic ones that try and explain things from the ground up).


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## xiphius (Feb 24, 2019)

TyroneGenade said:


> Thanks, but with one more tube and some CO2 it looked even better:



Very nice!

Yeah, one day I will take the plunge and set up a pressurized CO2 system. I have dabbled with DIY CO2 systems before, but they are usually a pain to maintain and keep consistent, so lately I have just gone the "low tech" route (easier to keep stable imo).


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## masaccio (Feb 25, 2019)

shade131 said:


> Really appreciate all the information. Over the last few days I’ve slowly been coming to the realization that I have way more lighting than I need. I’ll be able to get hard data when my PAR meter shows up, but I’m pretty confident that I’m growing paphs under dendrobium or cattleya light levels. I’m going to have to completely overhaul my setup to be able to hang the lights higher. What’s interesting is that while I noted that several burned (largely delenatii or its hybrids - I thought parvis would be less likely to burn?) 80% are doing really well. Maybe a few here or there that are a bit bleached out, but many have spiked. Watering a good bit, Humidity 50-70%, temp 55-70, and a ton of airflow. Maybe all that adds up to them tolerating more light than normal. I’ll post some pictures later. Have a good weekend everyone.



Since this thread has begun, I've run across some helpful articles by Eric Runkle. I found this one to be current, concise and interesting, which discusses simple technology for different types of white LEDs and includes graphs of wavelengths emitted along with a good discussion: https://gpnmag.com/article/white-leds-for-plant-applications/. 
He has written other articles as well, which can be Googled. Also, I've had time to experiment with my line-up of 250 watt equivalent white LEDs that were stressing all of my plants. I hoped not to have to replace the bulbs due to over-brightness. I lifted them to approximately 24"-26" above the tops of plants, give or take depending on light preferences. The bonus is that coverage is more even. The PPFD readings have all come more into line with those of successful growers (who posted in this thread - thank you!). The footcandle readings are is still high, but shade-lovers are not showing stress. The second part of the fix was decreasing illumination to around 12 hours per day. All of this can be further fine-tuned over time, but the danger seems to be over. Plants are proceeding nicely, with zero symptoms of over-lighting. Everything feels more nicely balanced and flexible. A spiking miltoniopsis bought at a show two weeks ago has continued to develop a perfect long spike and buds are preparing to open without any signs of stress or drying. So, in summary, thanks to Mr. Runkle, I have a better understanding of what my LEDs are providing, and thanks to this thread I'm providing a nicer growing environment for all of my plants. I hope some of this feedback might be helpful. Thanks.


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## masaccio (Feb 27, 2019)

terryros said:


> I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.\



Thanks so much for your recommendation of these bulbs, and the detail you've given on how you use them. Just a quick follow-up question, if I may. Do the orchids under these bulbs receive any natural light, other than ambient room light? It seems that these bulbs would offer very little wavelength in the red-spectrum and just wondered if plants might be receiving this from another source. Thanks!


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## terryros (Feb 28, 2019)

There is a window in my basement plant room, so some plants would get a little natural light but most would get none of it. I think that others have also found that natural white or true white LED bulbs must have sufficient red and blue spectrum because growth and blooming seems to be acceptable. The Apogee Quantum meter that I use cannot tell me how much of any part of the spectrum is being delivered, but it is supposed to tell me the micro moles/m2/sec being delivered within the 389-692 wavelength interval. Obviously, everything could be in the shorter wavelength area, but since things look "natural" color to my eye (and to photographs) under the lights, I don't think that can be the case.


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## southernbelle (Feb 28, 2019)

masaccio said:


> Thanks so much for your recommendation of these bulbs, and the detail you've given on how you use them. Just a quick follow-up question, if I may. Do the orchids under these bulbs receive any natural light, other than ambient room light? It seems that these bulbs would offer very little wavelength in the red-spectrum and just wondered if plants might be receiving this from another source. Thanks!



I have the LED T-8 60 degree tube lights from Orchids Ltd and they are the spectrum of natural daylight 5,000 k. The spectrum is just beyond 390-700 wavelength, so balanced red and blue. My room has zero ambient light because of no windows. I use the same PAR as terry ros. 3 bulb fixture above catts and 1 above phals and paphs. Lights are about 20”-24” above canopy. These are high intensity, give great light, so nice headroom. No problem blooming catts, paphs or Phals. I just showed this Catt Dinard ‘Blue Heaven’ at the Va Orchid Soc Show and won second in class. The flower was 6.25” across with a 2.75” lip. Young plant so only one flower but it was spectacular.


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## shade131 (Feb 28, 2019)

First of all, this thread has managed to increase my knowledge LED lighting regarding orchid by an order of magnitude. So that's a win. 

I'll keep updates coming, but for now I going with the old adage " as much light as the plants can handle without burning" while being careful to ease new plants into it. That winds up being a range of 120(maudiaes and mottled species)-300 (multis/parvis/phrags) PAR at the leaves. 90 degree angle lights. (still not clear on how beam angle relates to PAR?) Got a few in spike right now ( Paphs Berenice, Julius, delanatii and Hung Sheng Tango, and Phrag Eric Young) so if none of those blast, I'll know I'm at least close. 

My hunch at present is that after raising the lights I'm still at the high end of the range for all of them. If I took away air flow or humidity or increased photo period, I bet some would burn, which is kind of a problem since it's winter and I'd like to increase the day length come summer. I'll have to do some research to figure out which of mine are sensitive to day length vis a vis flowering before deciding if it's worth the risk to increase the length of the day. The main thing I don't want to do is burn anymore leaves. Just ruins the look of the plants. I have a big P callosum that I scorched, and it'll be a couple of years before it'll replace all of the burned leaves. 

-Brandon


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## shade131 (Feb 28, 2019)

southernbelle said:


> I have the LED T-8 60 degree tube lights from Orchids Ltd and they are the spectrum of natural daylight 5,000 k. The spectrum is just beyond 390-700 wavelength, so balanced red and blue. My room has zero ambient light because of no windows. I use the same PAR as terry ros. 3 bulb fixture above catts and 1 above phals and paphs. Lights are about 20”-24” above canopy. These are high intensity, give great light, so nice headroom. No problem blooming catts, paphs or Phals. I just showed this Catt Dinard ‘Blue Heaven’ at the Va Orchid Soc Show and won second in class. The flower was 6.25” across with a 2.75” lip. Young plant so only one flower but it was spectacular.



Wow that is a stunning flower. Well done. How long will that bloom last?......I finally gave up on the few Cattleyas that I had after fighting a scale infestation for months, but man those flowers are hard to beat.


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## masaccio (Feb 28, 2019)

terryros said:


> There is a window in my basement plant room, so some plants would get a little natural light but most would get none of it. I think that others have also found that natural white or true white LED bulbs must have sufficient red and blue spectrum because growth and blooming seems to be acceptable. The Apogee Quantum meter that I use cannot tell me how much of any part of the spectrum is being delivered, but it is supposed to tell me the micro moles/m2/sec being delivered within the 389-692 wavelength interval. Obviously, everything could be in the shorter wavelength area, but since things look "natural" color to my eye (and to photographs) under the lights, I don't think that can be the case.



Thank you very much for responding. I'm planning a second setup with very little natural light. I wanted to try the these ALT bulbs that you've written about. Feeling good about this now.


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## southernbelle (Mar 1, 2019)

shade131 said:


> Wow that is a stunning flower. Well done. How long will that bloom last?......I finally gave up on the few Cattleyas that I had after fighting a scale infestation for months, but man those flowers are hard to beat.


I fought scale that came in on 3 plants until I learned to spray 3 times in a row, 7-10 days apart. Scale gone. It opened 2/13 and is still in bloom. Last bloom was last Nov and lasted 3 weeks. Flower is getting nicer with each bloom, or could be that cooler winter temps of hi 72 low 63 allowed for more growth before opening.


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## Ray (Mar 1, 2019)

shade131 said:


> (still not clear on how beam angle relates to PAR?)


It doesn't.

First of all, PAR is the wrong term. PAR simply means the light is between 400 & 700 nm wavelength. What you're trying to determine is the PPFD (photosynthetic photon flux density) - the volume of light in the PAR spectrum reaching your plants per unit time, expressed in µmoles-per-square meter-per-second.

The PPF - the flux or volume of photons leaving the light per unit time - might be the same for different beam angle bulbs, but those photons are "spread out" more with the larger beam angle, so there are fewer per unit area hitting the plant.

If one of the lamps illuminated a circle 2 feet in diameter (area = 3.14 square feet) at a certain height, and the other illuminated a circle 4 feet in diameter (area 12.57 square feet) from that same height, The PPFD of the broader-beamed lamp would be 1/4 of that for the narrower one because the area illuminated is 4x larger.


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## southernbelle (Mar 1, 2019)

By the way, I was a bit off on the color spectrum I reported earlier for my T8 5,000 k LEDs. I remembered I had written the manufacturer and they sent me this graph. No problem blooming things with these lights.


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## shade131 (Mar 1, 2019)

Thanks for the clarification, Ray. Between what you wrote and what I found on wikipedia, it finally clicked - why conflating PAR and PPFD is misleading and causes confusion:

*"The irradiance of PAR can be measured in energy units (Watts/m2)*, which is relevant in energy-balance considerations for photosynthetic organisms........However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the *number* of photons than the *energy* contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD)

Lightbulb! haha...


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## masaccio (Mar 1, 2019)

southernbelle said:


> I have the LED T-8 60 degree tube lights from Orchids Ltd and they are the spectrum of natural daylight 5,000 k. The spectrum is just beyond 390-700 wavelength, so balanced red and blue. My room has zero ambient light because of no windows. I use the same PAR as terry ros. 3 bulb fixture above catts and 1 above phals and paphs. Lights are about 20”-24” above canopy. These are high intensity, give great light, so nice headroom. No problem blooming catts, paphs or Phals. I just showed this Catt Dinard ‘Blue Heaven’ at the Va Orchid Soc Show and won second in class. The flower was 6.25” across with a 2.75” lip. Young plant so only one flower but it was spectacular.



Wow, Nice job on the Blue Heaven! I've felt "stuck" with spotlight type LEDs because I love the flexibility and I think they look kind've cool. But I'm becoming more tempted to try the tube lights, and they would be easier to set up in my second location. Thanks for the great info.


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## Ray (Mar 1, 2019)

shade131 said:


> Thanks for the clarification, Ray. Between what you wrote and what I found on wikipedia, it finally clicked - why conflating PAR and PPFD is misleading and causes confusion:
> 
> *"The irradiance of PAR can be measured in energy units (Watts/m2)*, which is relevant in energy-balance considerations for photosynthetic organisms........However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the *number* of photons than the *energy* contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD)
> 
> Lightbulb! haha...


Just don't think that the "watts" used in that definition has anything to do with the wattage of the lamp.


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## naoki (Mar 1, 2019)

Ray said:


> Just don't think that the "watts" used in that definition has anything to do with the wattage of the lamp.



Hmm, strictly, they are the same unit, so they can be comparable. For example when you calculate the efficiency of a lamp, you calculate the emitted energy in light (watts) against the input electricity energy (watts). So the unit of efficiency is %. High quality LEDs can achieve around 60% efficiency (40% of electric energy becomes heat). This is relevant when you are designing how to deal with the heat.

Note "efficiency" is different from "efficacy", efficacy is measured in terms of lumen/W or micromol/J (note W = J/s), not %. In other words, with efficacy, you are comparing non-equivalent quantities.

In terms of photosynthesis, photosynthetic photon (or quantum) efficacy (PPE, measured in terms of micromol/J) is more important than efficiency by itself since it is mostly a quantum process as the Wikipedia quote mentions. Blue LEDs could have high efficiency, but in terms of PPE, red LEDs have a higher efficacy in general.


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## Ray (Mar 2, 2019)

Naoki, while the watts may be the same unit, I think your explanation supports my contention that the watts of the lamp are not the "irradiance of PAR" watts hitting the plants.


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## naoki (Mar 2, 2019)

Ray, you are correct; irradiance (in terms of W/m^2) is proportional to radiant flux (watt, the total light output from the bulb), which is the (lamp watt) * efficiency (%). So they are not the same, but there is a relationship between them (my only objection was "anything to do with" part).

Then irradiance measured in watts are not a good measurement in terms of photosynthesis.

People should be aware that so-called "spectrum plot" (spectral power distribution, SPD) is frequently expressed in terms of watts (as shown earlier in the thread). So you need to convert it to number of photons before you use it for photosynthetic purpose (illustrated in here). If you make the conversion, blue peaks becomes quite a bit smaller.


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## terryros (Mar 5, 2019)

Ray said:


> It doesn't.
> 
> First, I agree with Ray that what we are measuring with our Apogee quantum meters is peak photon flux density. Apogee reports the response of the meter for the PAR range of light frequency, which seems to imply that the meter is only/mostly measuring within this range. However, I see how it is possible that the meter is still measuring a wider range of frequencies.
> 
> Second, if I were home, I could give the several references that I found to research into the effect of collimated versus diffuse light of the same intensity on photosynthetic responses of plant leaves. The more collimated the light, the greater the photosynthetic response to the same photon density. This is the only explanation I have for why I can grow my Phals very well and to large size with excellent blooming with measured peak photon density of only about 50 at the top of the leaves using 40 degree beam angle lights. I get excellent results with Phrags at 60-80 peak photon density. These values are definitely lower than what has been obtained in greenhouse conditions with diffuse natural light. My Cattleyas are under 60 degree beam angle bulbs but I think this may still lower the required peak photon density compared to diffuse light.


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## terryros (Mar 5, 2019)

Nuts, should have added that I think the collimated/vertical light effect may apply most to plants with mostly horizontal leaves, like many Phals. With my large flowered, unifoliate Cattleyas, the collimated light is probably passing somewhat parallel to many leaves, eliminating this effect. I think that is why I am finding that it takes 200-400 micromoles/m2/sec to get excellent growth and blooming, which is in agreement with the small amount of data published with natural light.


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## xiphius (Mar 5, 2019)

shade131 said:


> Thanks for the clarification, Ray. Between what you wrote and what I found on wikipedia, it finally clicked - why conflating PAR and PPFD is misleading and causes confusion:
> 
> *"The irradiance of PAR can be measured in energy units (Watts/m2)*, which is relevant in energy-balance considerations for photosynthetic organisms........However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the *number* of photons than the *energy* contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD)
> 
> Lightbulb! haha...



Yeah, this thread has really helped clarify some things for me as well. Thanks all! The distinction that PAR, itself, is not the measurement is lacking in many sources (or is very subtle and easily missed/confused). This whole thread is a pretty great discussion. I hadn't even considered the watts versus number of photons side of things.


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## naoki (Mar 5, 2019)

Terry, I think one of the papers you are talking about is this (from the previous discussion):

Brodersen, C. R., Vogelmann, T. C., Williams, W. E., & Gorton, H. L. (2008). A new paradigm in leaf‐level photosynthesis: direct and diffuse lights are not equal. _Plant, cell & environment_, _31_(1), 159-164. (link)

We have to be careful about how to interpret the results. This paper showed that at the *leaf level*, when the light is hitting the leaf perpendicularly, photosynthetic (PS) rate can be higher. The possible reason is that the penetration of the light to the deeper layers. There are several layers of cells in a leaf, and a layer with something called pallisade parenchyma cells is the most relevant for PS (in non C4 plant). This layer in leaves which acclimated to intense light become thick. Even within an individual, they can develop these different leaves (i.e. the part exposed to strong light develops "sun leaves", but shady part remains "shade leaves"). When there is a thick layer of pallisade parenchyma, the light hitting at an angle can't reach to the deepest cells. Therefore, the perpendicular light is better for PS. The difference was very small (10-15%). But when they tested with the shade leaves of the same species, the advantage is not observed. This is a a side note, but the same logic apply to explain why green light can enhance the overall PS rate in some situations (under intense light) since it can penetrate into the deeper region.

But you should be aware that at a *plant (or community) level*, there are data showing advantage of diffused light (cited in the paper). This is probably obvious; leaves are not always perpendicular to the light, so with diffused light, some light is going to hit the leaf at 90 degree angle, penetrating deeper. More importantly, with diffused light, you can avoid the shading effect (the leaves closer to the light source can shade the lower leaves). These are the reasons, that both in greenhouse and with artificial light, diffused light gives better growth. This is one of the reasons I now prefer linear modules (or pannels) of mid-power LEDs over COB although in a reflective grow tent, the point source light like COB LEDs can produce somewhat diffused light.


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## terryros (Mar 6, 2019)

Naoki, I can believe that diffuse light has some advantages and I think that was one of the papers I had found. My LED experiment began because I had hit the maximum electricity load my plant room could handle using fluorescent fixtures and the heat produced by my lights was not compatable with needed temperature drops for blooming. I also wanted more head room over plants to accommodate bloom spikes and wanted to be able to grow higher light plants. LEDs have given me all of that. If I were to go to diffuse LED lighting, I think I would be losing more light out into non-growth areas of the room and I am again about at the maximum for electricity drain, so want as much of the photons going to the plants as possible. Thus, more focused light is a benefit for me. I am working on a plan to run more electricity to the room. Then maybe I could experiment with some more diffuse light sources.


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## southernbelle (Mar 6, 2019)

terryros said:


> Naoki, I can believe that diffuse light has some advantages and I think that was one of the papers I had found. My LED experiment began because I had hit the maximum electricity load my plant room could handle using fluorescent fixtures and the heat produced by my lights was not compatable with needed temperature drops for blooming. I also wanted more head room over plants to accommodate bloom spikes and wanted to be able to grow higher light plants. LEDs have given me all of that. If I were to go to diffuse LED lighting, I think I would be losing more light out into non-growth areas of the room and I am again about at the maximum for electricity drain, so want as much of the photons going to the plants as possible. Thus, more focused light is a benefit for me. I am working on a plan to run more electricity to the room. Then maybe I could experiment with some more diffuse light sources.


When I spoke to the seller about the lights, he mentioned that there is research that these (Aeon 60 degree T-8) lights actually penetrate the top leaves to also give light to lower leaves they are shading. Much of this discussion is way over my head from a technical standpoint, but what I can say is how well they grow phals, paphs and catts using the PAR readings you mention for each type (as measured at top of leaf canopy on the Quantum PAR meter you use). Many of my plants show the purple shading/spotting of maximum light levels on their leaves. Especially the phals and catts with thicker leaves.


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## naoki (Mar 6, 2019)

terryros said:


> Naoki, I can believe that diffuse light has some advantages and I think that was one of the papers I had found. My LED experiment began because I had hit the maximum electricity load my plant room could handle using fluorescent fixtures and the heat produced by my lights was not compatable with needed temperature drops for blooming. I also wanted more head room over plants to accommodate bloom spikes and wanted to be able to grow higher light plants. LEDs have given me all of that. If I were to go to diffuse LED lighting, I think I would be losing more light out into non-growth areas of the room and I am again about at the maximum for electricity drain, so want as much of the photons going to the plants as possible. Thus, more focused light is a benefit for me. I am working on a plan to run more electricity to the room. Then maybe I could experiment with some more diffuse light sources.



Yes, minimizing spill-over at the edges of the grow area does influence the "effective efficacy" a little bit. Some people do use a narrow beam angle at the margin of the grow area, and wider angles in the middle. But it won't work too well with a relatively narrow/small area.

Sounds like that you might get better benefits from higher efficacy LEDs. There is a huge difference in efficacy among LEDs. The better one can give around 2.7 micromol/J while many of them are around 1.2 micromol/J (just slightly above T8, which is around 0.8-0.9 miromol/J). So you can get the same amount of light with a half of the total electricity consumption.


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## Ray (Mar 7, 2019)

The best way - from the plants' perspective (literally & figuratively) - to achieve quality lighting is to provide multiple light emitters spread out over a broad area from high up, so you get the maximum "spread" to the light. Adding lighting that is at angles off of vertical at the perimeter also helps, as does having white walls.

Yes, that means more wattage, but you have to weigh your priorities.


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## masaccio (Mar 29, 2019)

terryros said:


> I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don&rsquo;t grow many Paphs. Of course I have been tweaking potting mix and nutrition over this period of time, but I have kept the PAR reading at 80-100 at the leaf tops. My LEDs have a focused light beam of 40 degrees and a little data suggests that this more vertical light reduces the required intensity needed for photosynthesis. My Phalaenopsis receive only about 50 with the same 40 degree bulbs while my Cattleyas are given between 250-400 (depending on the species) at the leaf tops using 60 degree angle focused bulbs.
> 
> 
> Sent from my iPad using Tapatalk Pro


terryros, I'm in the process of doing a track light install with the ALT MR16s. Since they're LEDs, I was assuming they are low voltage, but (DUH) since you can use them in standard household screw-in fixtures, they're regular 120 volt. Is that right? Thanks!


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## terryros (Mar 29, 2019)

My electricity knowledge is weak, but my 40 degree angle MR16 bulbs from ALT are 7 watts by specifications. They work in standard track lighting fixtures. I currently have about 30 of these bulbs. I use them up high over Phals, Phrags, Paphs, and Miltoniopsis so they accommodate almost all spikes.


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## masaccio (Mar 29, 2019)

terryros said:


> My electricity knowledge is weak, but my 40 degree angle MR16 bulbs from ALT are 7 watts by specifications. They work in standard track lighting fixtures. I currently have about 30 of these bulbs. I use them up high over Phals, Phrags, Paphs, and Miltoniopsis so they accommodate almost all spikes.


Ha! Mine too. Jerry just got back to me as well, and confirmed this. Thanks for the quick response.


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## xiphius (Mar 30, 2019)

masaccio said:


> erryros, I'm in the process of doing a track light install with the ALT MR16s. Since they're LEDs, I was assuming they are low voltage, but (DUH) since you can use them in standard household screw-in fixtures, they're regular 120 volt. Is that right? Thanks!



Do you need them to be low volatge? Most LEDs I have seen are advertised as low _wattage_. If it screws into a normal household fixture, it will be using 120 V (or has internal circuitry to convert from 120 V AC > 12 V DC). However, if it is low wattage then it will be pulling less current (since wattage is voltage * amperage). That's my understanding at least.


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## southernbelle (Mar 30, 2019)

masaccio said:


> terryros, I'm in the process of doing a track light install with the ALT MR16s. Since they're LEDs, I was assuming they are low voltage, but (DUH) since you can use them in standard household screw-in fixtures, they're regular 120 volt. Is that right? Thanks!


My ALT 4’ tube LEDs use 42 watts each. I have 3 tube fixtures made for LEDs (from same company as tubes) as ballast is different, as I understand it. (Frankly, I am way out of my league here, just repeating what I was told when I bought them re ballast). Here are the specs re Watts/volts/etc. on each tube’s sticker:
T8 tube V4 IP 68
Power consumption: 42 W
Input: AC 100V to 277V ~ 50/60 Hz 
80-330 mA
Not suitable for dimming
Hope this adds clarity.


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## Silverwhisp (Mar 31, 2019)

A couple of years ago, Orchids Ltd. set me up with MR16 V6 72 degree bulbs for my orchids. Shelving was 30” apart, and 36” wide. The height worked for all orchids but for my Phrag. Sorcerer’s Apprentice. 

For high-light orchids, I used 2 bulbs; lower light, one bulb. They recommended one bulb above Phrags. 

After being underwhelmed by the results for my Phrags, I noticed on their website that they no longer sell that particular bulb, but now sell a “stronger” one. Once I added 2 bulbs, fairly evenly spaced above my Phrags, things really took off.

Some of us are just learning about LED lighting through trial and error. At least, I am.


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## Ray (Mar 31, 2019)

If lamp makers would 1) Provide their lamps' output in terms of photon flux (µmol/sec) and provide intensity maps (see blow), then it would be easy!


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## terryros (Mar 31, 2019)

I agree, Ray. Debra and I had to do that mapping manually with our bulbs and that is only the start. Then you have to figure out the correct LED light intensity for each type of orchid. Almost all of the published literature with photon flux and daily light integral requirements of various orchid types was done with natural light, almost always in a greenhouse setting. At least with the LED bulbs I have used, I can get acceptable growth and blooming with light intensity and daily light integrals that are less than published numbers. It has taken me years of fiddling to start to get closer to optimum in terms of light intensity and that is probably only for my particular environment and cultural conditions!


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## masaccio (Mar 31, 2019)

terryros said:


> I agree, Ray. Debra and I had to do that mapping manually with our bulbs and that is only the start. Then you have to figure out the correct LED light intensity for each type of orchid. Almost all of the published literature with photon flux and daily light integral requirements of various orchid types was done with natural light, almost always in a greenhouse setting. At least with the LED bulbs I have used, I can get acceptable growth and blooming with light intensity and daily light integrals that are less than published numbers. It has taken me years of fiddling to start to get closer to optimum in terms of light intensity and that is probably only for my particular environment and cultural conditions!



My initial response to this is, "Kill Me Now." I've mentioned that I'm working with Orchids Limited for a couple of long and narrow setups. I bought a few of the 7-watt MR16s at 720 lumens each (they're around 5000k). There is an online chart that recommends these bulbs for medium-high light orchids (which to me translates as cattleya light) at a distance of 3 feet. So at a distance of 32" my meter is measuring UNDER 30 PPFD directly under the bulb. At about 15" it measures around 60. Does it seem reasonable to anyone that these bulbs are suitable for "medium-high" light orchids??


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## masaccio (Mar 31, 2019)

Silverwhisp said:


> A couple of years ago, Orchids Ltd. set me up with MR16 V6 72 degree bulbs for my orchids. Shelving was 30” apart, and 36” wide. The height worked for all orchids but for my Phrag. Sorcerer’s Apprentice.
> 
> For high-light orchids, I used 2 bulbs; lower light, one bulb. They recommended one bulb above Phrags.
> 
> ...



Yes, I'm just learning myself. Although I think the correct phrase for me is that I'm NOT learning, or that's how it feels anyway! Oh, wait. You meant a 720 LUMEN bulb, right? I haven't seen a "72 degree" bulb. You probably have a 40 degree bulb that is supposed to cover medium high light orchids within a 32 inch space at 3 feet overhead. At any rate, experience is gold. Would you provide a little more detail about the specific plants you're growing in the setup you described? When you say "high light" orchids, which specific ones are you referring to? Thank you!


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## terryros (Mar 31, 2019)

I need 200-400 micromoles/m2/sec peak photon intensity at the top of Cattleya leaves to get good growth and blooming. You cannot get that with the MR16 bulbs at 3 feet! At the height were the intensity is high enough, you are not very high over the plants and the foot print is not very wide. I only use the 7 watt MR16 for lower light orchids where 50-80 micromoles/m2/sec gets the job done. For Cattleyas I am using 60 degree 15 or 20 watt ALT bulbs at 6-12 inch heights depending on which bulb to get the 200-400 intensity. I would not try and do Cattleyas with the MR16, 7 watt bulbs.


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## Silverwhisp (Apr 1, 2019)

masaccio said:


> Yes, I'm just learning myself. Although I think the correct phrase for me is that I'm NOT learning, or that's how it feels anyway! Oh, wait. You meant a 720 LUMEN bulb, right? I haven't seen a "72 degree" bulb. You probably have a 40 degree bulb that is supposed to cover medium high light orchids within a 32 inch space at 3 feet overhead. At any rate, experience is gold. Would you provide a little more detail about the specific plants you're growing in the setup you described? When you say "high light" orchids, which specific ones are you referring to? Thank you!



The beam angle is 72 degrees; that is what is meant by the specification.

When Orchids Limited said to me “high light” orchids, they included Catts in that category.

What I’ve got under the 2-bulb, 36”- wide, 30” - high shelf: Phrags: Frank Smith; Cardinale; Magdalene Rose; Eumelia Arias; Elizabeth Castle; Betheva; After-Glo; NoID Besseae hybrid; Schroederae; Green Hornet; Eric Young. I also have a couple of Disas there, but I’m thinking they could be a bit closer to the bulbs, so will raise them up a bit. This is my first foray with Disas, though, so I’m not absolutely sure. The orchids on this shelf sit at an east-facing window, FYI.


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## Silverwhisp (Apr 1, 2019)

terryros said:


> I need 200-400 micromoles/m2/sec peak photon intensity at the top of Cattleya leaves to get good growth and blooming. You cannot get that with the MR16 bulbs at 3 feet! At the height were the intensity is high enough, you are not very high over the plants and the foot print is not very wide. I only use the 7 watt MR16 for lower light orchids where 50-80 micromoles/m2/sec gets the job done. For Cattleyas I am using 60 degree 15 or 20 watt ALT bulbs at 6-12 inch heights depending on which bulb to get the 200-400 intensity. I would not try and do Cattleyas with the MR16, 7 watt bulbs.


So, for lower light orchids, if you had the MR16, 7-watt, bulbs at 36” height, which orchids might you expect to grow and bloom well?


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## Ray (Apr 1, 2019)

I don't think you'd grow and bloom very much well with those tiny lamps at that height. Masaccio's measurement was "under 30" micromoles/sq. m/sec. Multiply by 5 to get a gross estimation of footcandles - not much does all that well under <150 fc.

That said, I am surprised that Terry gets good cattleya growth and flowering at only 200-400 micromoles/sq. m/sec. Full sun is about 2000.


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## masaccio (Apr 1, 2019)

terryros said:


> I need 200-400 micromoles/m2/sec peak photon intensity at the top of Cattleya leaves to get good growth and blooming. You cannot get that with the MR16 bulbs at 3 feet! At the height were the intensity is high enough, you are not very high over the plants and the foot print is not very wide. I only use the 7 watt MR16 for lower light orchids where 50-80 micromoles/m2/sec gets the job done. For Cattleyas I am using 60 degree 15 or 20 watt ALT bulbs at 6-12 inch heights depending on which bulb to get the 200-400 intensity. I would not try and do Cattleyas with the MR16, 7 watt bulbs.



I totally trust your experience and am relying on it. I'm not suggesting I would use the MR16s for cattleyas (ideally). I've actually already replaced the MR16s that were over my cattleyas with my old 2650 lumen spots for the time being. The spectrum isn't the best but a bit of natural light is helping. HOWEVER , the question still remains of rectifying these MR16s with the distance recommendations posted for these lights. Jerry insists repeatedly, against my stubborn skepticism, that these bulbs are effective at surprising distances. I trust him. I just don't understand it and it will bug me until I do.

LEDs register convincingly on a foot-candle meter. When I measure my MR16s with a footcandle meter at 32 inches, I get a reading of about 1500 directly under the bulb. Tagging onto comments Ray has made about downwardly adjusting plant light intensity requirements when converting from natural to artificial light, a constant supply of 1500fc under artificial light for 12 hours every day would theoretically suffice for a plant rated as needing 3000fc of natural daylight. So, maybe the specifications posted for these MR16s are based on footcandle readings and are assuming a constant supply of this light for 12 hours per day making up the other 1500fc. Maybe even extending the time a little bit but I don't think this is recommended.

So, I have a measly 35 micromoles/m2/s at a distance of 32 inches from these bulbs. When I measure natural light at 3000fc, and then measure that same 3000fc with a PPFD meter, I receive a yield of about 70 micromoles/m2/s. Measuring directly under the MR16 with a footcandle meter at a distance of 32" registers about 1500fc (half the first reading under natural light). Measuring the same distance with a PPFD meter yields about 35 micromoles/m2/s as stated. So it seems that the proportion of micromoles/m2/s to footcandles at varying intensities remains constant and also applies to both natural light and artificial light of comparable quality. So given that the proposal is grow plants under artificial light yielding 35 micromoles/m2/s (or 1500fc) at a constant exposure of 12 hours every day, is it arguable that the MR16s would, after all, suit orchids requiring 70 micromoles/m2/s (or 3000fc) in natural light?


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## masaccio (Apr 1, 2019)

That last dubious statement of mine of course doesn't hold. Disappointlngly, the statement "micromoles/ms/s" is not directly correlated with footcandles. According to this theory for terryros to achieve his 200-400 micromoles/ms/s he would have to be applying more than 10,000 fc. Denial is a wonderful thing. But the general theory holds, that constant application of low light level compensates for plant ratings that are based the ebb and flow of natural light. It still seems apparent that the MR16 specifications are based on footcandles, not micromoles/ms/s. They stated that, as with all things orchids, improvement from using these bulbs would not be dramatic, but would be noticeable over a period of a few months. I can't fool around with cattleyas this time of year, which are either blooming, or are setting up put on new growth. I'm getting those micromoles AND footcandles one way or the other. I'm sure the elusive answer combines quantity as well as quality for higher energy plants.


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## terryros (Apr 1, 2019)

I use an Apogee Quantum meter. I don’t think there is an easy conversion from foot candles to the micromoles/m2/sec output from the meter and I don’t try to do this. The Apogee website implies, but isn’t certain, that the peak photon flux being measured is predominantly in the PAR frequency range. A footcandle meter would most likely not be doing this.

I need to be about 20 inches directly underneath an ALT MR16 7 watt true white bulb labeled as 720 lumens to get 50 micromoles/m2/sec. My Phalaenopsis grow and bloom well at or below this intensity. I give daylight varying from a peak of 13.5 hours in the summer and 11.0 hours in the winter. I grow and bloom Phrags under these bulbs with photon density of 60-80 micromoles/m2/sec. Daily light integrals for my Phals would range from about 2.0-2.4 per day (units omitted). These are very far away from anything published as adequate for high light orchids like Cattleyas. I use ALT 15 or 20 watt, 60 degree bulbs for my Cattleyas giving me peak photon flux at the top of the leaves of 300-400 and daily light integrals between 10-14.

I have to admit that I have never, in the 8 years that I have been using the MR16s, attempted to use them to grow Cattleyas! So, I can’t prove that they wouldn’t get the job done! Perhaps I am giving Cattleyas excessive light, but I do not have leaf signs to indicate this. I will continue to think that the MR16 are great bulbs for lower light orchids that need great head room over the plants to accommodate spikes.


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## Ray (Apr 2, 2019)

terryros said:


> I use an Apogee Quantum meter. I don’t think there is an easy conversion from foot candles to the micromoles/m2/sec output from the meter and I don’t try to do this. The Apogee website implies, but isn’t certain, that the peak photon flux being measured is predominantly in the PAR frequency range. A footcandle meter would most likely not be doing this.
> 
> I need to be about 20 inches directly underneath an ALT MR16 7 watt true white bulb labeled as 720 lumens to get 50 micromoles/m2/sec. My Phalaenopsis grow and bloom well at or below this intensity. I give daylight varying from a peak of 13.5 hours in the summer and 11.0 hours in the winter. I grow and bloom Phrags under these bulbs with photon density of 60-80 micromoles/m2/sec. Daily light integrals for my Phals would range from about 2.0-2.4 per day (units omitted). These are very far away from anything published as adequate for high light orchids like Cattleyas. I use ALT 15 or 20 watt, 60 degree bulbs for my Cattleyas giving me peak photon flux at the top of the leaves of 300-400 and daily light integrals between 10-14.



The "5 factor" comes from Apogee's website. Full, noontime sun is about 10,800 fc and 2000 µmol/m2/sec. It's a "crap estimate" comparing apparent brightness to actual photon density, but it's all we have for translating form culture guides.

They show graphs of the spectral sensitivity of their quantum sensors, so I don't under stand the uncertainty comment.

There are a few aspects of light measurement that makes it difficult to translate from one scale to another, not to mention one light meter to another.

When we see a lamp labeled as "X lumens (or lux)" output, it is the apparent brightness of the lamp, that is, how bright it appears to the human eye, right at the surface of the bulb. As we move farther from the bulb, it looks less bright (and is) due to the "spreading out" of the photons, which holds true for any light measurement. PLUS - the spectrum also plays a role, as the human eye is most sensitive in the green portion of the spectrum. If we have two "white" lamps with identical photon outputs, but one has more green in its spectrum, it will appear brighter. Most light meters are designed to match human perception.

When we start talking photon flux, µmol/second, lamp comparison is linear - differences are literal, not apparent. The flux density, moreover, also decreases with distance due to photon "spread". A point light source - ANY light source - radiating in all directions, exhibits the same inverse-square relationship in light intensity (or density, if you will). Physical design and reflectors, however, can certainly affect that. Working backwards from Terry's measurement, 50 µmol/m2/sec x 5 = 250 foot-candles using the Apogee factor, and considering the directionality of the lamps, that's not out of the realm of possibility at all.

Quantum meters for plant light measurement merely have the measured portion of the spectrum limited by filters, and are linear in that range, i.e., not enhanced sensitivity for green wavelengths.


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## Silverwhisp (Apr 2, 2019)

Although I don’t have a meter - yet - it might be helpful to others to View attachment 15039
know distance from bulb to plant leaf. E.g., in my case, although the vertical shelf spacing is 30”, the MR 16’s are 11” from Phrag. Frank Smith. 

I think it’s working:


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## masaccio (Apr 2, 2019)

terryros said:


> I use an Apogee Quantum meter. I don’t think there is an easy conversion from foot candles to the micromoles/m2/sec output from the meter and I don’t try to do this. The Apogee website implies, but isn’t certain, that the peak photon flux being measured is predominantly in the PAR frequency range. A footcandle meter would most likely not be doing this.
> 
> I need to be about 20 inches directly underneath an ALT MR16 7 watt true white bulb labeled as 720 lumens to get 50 micromoles/m2/sec. My Phalaenopsis grow and bloom well at or below this intensity. I give daylight varying from a peak of 13.5 hours in the summer and 11.0 hours in the winter. I grow and bloom Phrags under these bulbs with photon density of 60-80 micromoles/m2/sec. Daily light integrals for my Phals would range from about 2.0-2.4 per day (units omitted). These are very far away from anything published as adequate for high light orchids like Cattleyas. I use ALT 15 or 20 watt, 60 degree bulbs for my Cattleyas giving me peak photon flux at the top of the leaves of 300-400 and daily light integrals between 10-14.
> 
> I have to admit that I have never, in the 8 years that I have been using the MR16s, attempted to use them to grow Cattleyas! So, I can’t prove that they wouldn’t get the job done! Perhaps I am giving Cattleyas excessive light, but I do not have leaf signs to indicate this. I will continue to think that the MR16 are great bulbs for lower light orchids that need great head room over the plants to accommodate spikes.



This make sense. I may be getting a little bit of a feel for this. The problem now facing me is that I've ordered track lighting for an 11 foot long, 12" deep orchid "shelf" setup in another room. It will be a paph garden, and perhaps a few other plants that are light compatible. I absolutely need enough light for the higher light polyanthas -- philippinense and the like. So the light will have to be securely medium in intensity - not just the low medium that one usually thinks of for paphs. Perhaps your phrags also fall into this somewhat higher light category.

The track and fixtures ordered are line voltage, and the fixtures are just the sockets so I can substitute out normal household bulbs freely. Based on recommendations, I was planning on using 30 degree MR16s for these plants. If I mount the track directly overhead, the fixtures will be approximately four feet above the plants, or slightly less. I wanted to pull the track out a little bit so the plants receive some side lighting as well. This might add 6-8 inches distance. I'm beginning to feel that using MR16s for this setup, even the 30 degree, is wishful thinking. My gut impulse at this point is to use 2650 lumen spots at 5000K. If they're a little too bright, and they may not be, I could dim them down a little. 

Orchids Limited is stgrongly recommending the 30 degree MR16s, and naturally I respect the opinions offered but am having a failure of confidence in these bulbs at the distance I am proposing. Any insights, recommendations would be greatly appreciated. The track will be installed in a few days; I have to decide whether I have to mount directly overhead or whether I can afford to pull the track out a little. I guess the bulbs can be selected a little later.


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## Ray (Apr 2, 2019)

If Terry measured 50µmoles/m2/sec at 20", then you can expect no more than 12 or so at 40", and less at 48" or more. Realize, however, that if you increase the number of lamps, you increase that. Four of them aimed at the same area from 40" would give the same PPFD that Terry measured for one at 20".


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## shade131 (Apr 3, 2019)

masaccio said:


> My initial response to this is, "Kill Me Now." I've mentioned that I'm working with Orchids Limited for a couple of long and narrow setups. I bought a few of the 7-watt MR16s at 720 lumens each (they're around 5000k). There is an online chart that recommends these bulbs for medium-high light orchids (which to me translates as cattleya light) at a distance of 3 feet. So at a distance of 32" my meter is measuring UNDER 30 PPFD directly under the bulb. At about 15" it measures around 60. Does it seem reasonable to anyone that these bulbs are suitable for "medium-high" light orchids??



That doesnt sound like enough light at all. You'll need around 150 for medium light - very rough estimate.


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## masaccio (Apr 3, 2019)

Well, I've heard it over and over again, now. I guess it's time for Plan B. Thinking to mount the track on a rear wall, a bit farther down, instead of on the ceiling. Will have to figure out a way to bring it out a bit so the bulbs are over the plants. I wouldn't mind a little side lighting in theory, but if I did this from the rear wall, the bulbs would be pointing into the room. Not good. I also could do the same arrangement I have in my first setup - with spots hanging from a curtain rod. The adjustability is great, but not a very clean look, with all the wires. Thanks for the responses.


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## masaccio (Apr 3, 2019)

Interesting. I took a series of comparison readings with both a foot candle meter and my PAR meter through a northeast window early this afternoon. Perfectly clear day, stable light conditions. Foot-candle meter registerd 2250fc. The PAR meter measured 23 μmols/m2/s. I chose a placement and angle that I could reasonably duplicate with both instruments and took several readings. Not being a light expert, I guess it's possible that this may have no meaning whatever. But if midday light at 2250fc also delivers 23 μmols/m2/s then it seems to stand to reason that this PPFD level is satisfactory to grow many medium-low light orchids.


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## Ray (Apr 3, 2019)

I think there must be a significant discrepancy in the light capture of the two meters. Full, noontime, summer sun is 10,800fc and 2000 µmol/m2/sec. The fc meter shows close to 20% of that while the PAR meter is closer to 1%.

Sump'n juss ain't raht.


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## terryros (Apr 3, 2019)

Ray, the Apogee material shows the sensitivity of the meter in the PAR range, but I wasn’t sure that this means the meter is only measuring photons within this range when it is reporting the output. I have always hoped this was the case, but saw how I could interpret it correctly. My Apogee meter has a setting for “electric” and a setting for natural light. I am not quite sure how this works either, but I think the variation in how footcandle and photon flux meters compare may have to do with the filters and settings for electric and natural light.

I have 7 MR16, 7 watt. 40 degree bulbs covering a 4 foot length of humidity trays. By geometry, I calculate that the height I am using covers about a 24 inch wide swatch down the trays. The intensity is highest at the center and under each light, but the overlap of the beams gives acceptable light to most of the leaves.


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## masaccio (Apr 3, 2019)

Ray said:


> I think there must be a significant discrepancy in the light capture of the two meters. Full, noontime, summer sun is 10,800fc and 2000 µmol/m2/sec. The fc meter shows close to 20% of that while the PAR meter is closer to 1%.
> 
> Sump'n juss ain't raht.



No idea. For the sake of argument, let's say that my meters are in the ballpark. Any other explanation for direct sun to have a higher rate of PPF than ambient light?


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## naoki (Apr 4, 2019)

terryros said:


> Ray, the Apogee material shows the sensitivity of the meter in the PAR range, but I wasn’t sure that this means the meter is only measuring photons within this range when it is reporting the output. I have always hoped this was the case, but saw how I could interpret it correctly. My Apogee meter has a setting for “electric” and a setting for natural light. I am not quite sure how this works either, but I think the variation in how footcandle and photon flux meters compare may have to do with the filters and settings for electric and natural light.



It is measuring the range indicated by the sensitivity curve. However, since the older Apogee didn't have a flat sensitivity curve, the spectra of light influence the reading. The error is largest when the light contains lots of deep red. So they have calibration coefficients for sun and artifical light (electric). With the newer Apogee (500 series), the response is fairly flat, and pretty similar to Li-Cor Quantum sensors. So they don't have to have the different coefficients.

Indeed, if you know the spectra, you can make the exact conversion coefficient. Apogee has some info here: https://www.apogeeinstruments.com/how-to-correct-for-spectral-errors-of-popular-light-sources/ But for the practical use, you don't have to worry about it. Bulk Reef Supply has a video (link) comparing the practical differences between old and new Apogee and LiCor. They use blue heavy light (for reef aquarium), but the cheap old Apogee is good enough.

Indeed, if you can get the sensitivity curve of cheap lux meter (and know the emission spectrum of the light), you can calculate the exact conversion factor to convert lux (or fc) to ppfd. But unfortunately, cheap lux meters don't provide the sensitivity information. Also they can deviate quite a bit from the standard luminosity function.

Massaccio, one of your meters are apparently broken or completely out of calibration. I would guess fc meter if you are measuring next to north facing window. Even if you have accidentally set it at lux instead of fc, it is still quite a bit off. With indirect light, the spectrum can be shifted compared to direct light, but you will not see that much deviation.


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## spujr (Apr 6, 2019)

I've been following this thread with interest because it is a subject I would (should) like to know more about.

I have a lumens reader (lux/FC) and made measurements around my growth area. For the most part, where my paphs are I am at 300-400fc, depending obviously where it is situated and how far away from the light. This reader was pretty consistent with the FC App reader one can get on their phone.

I thought these readings were low because I read in various places that paphs like armeniacums like around 1500fc. 

Well the plants don't seem to mind my conditions, all leaves are light green including the higher light requirement species like Cats, Neos (now vanda), and dendrchilumns.

I'm using a full spectrum ~300w quantum dot led, placed about 6ft up as my main source. I added 4, 13.5w strip leds to add light on the edge of the growth chamber. However, being placed 6ft high I don't think they contribute to much and planning to put them on a shelf system in another area in the future.

Apparently one gets more "bang for the buck" by using the 13.5w leds than the 300w one I got, where the 13.5ws only cost ~$30 apiece versus ~$800 for the other. However they would need to be placed closer to the plants. As for me, I got both for a cheap price through work so using what is given.


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## southernbelle (Apr 7, 2019)

spujr said:


> Well the plants don't seem to mind my conditions, all leaves are light green including the higher light requirement species like Cats, Neos (now vanda), and dendrchilumns.
> View attachment 15057
> View attachment 15057


How is your bloom? That would be the greater test than growth, I would think.


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## masaccio (Apr 11, 2019)

naoki said:


> Massaccio, one of your meters are apparently broken or completely out of calibration. I would guess fc meter if you are measuring next to north facing window. Even if you have accidentally set it at lux instead of fc, it is still quite a bit off. With indirect light, the spectrum can be shifted compared to direct light, but you will not see that much deviation.



I believe I stated a northeast window. I also have a digital fc meter that confirms the analog silicon sensor fc meter I was using. Taking another reading today, 2:00pm EDST, overcast day from inside, pointed at the sky next to a single-paned window. Getting readings from both meters in the 4500 4750 range. PAR meter is giving me 260 micromoles/m2/s. What say you? Thanks.


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## naoki (Apr 11, 2019)

Then your PAR meter is broken. I'm assuming that you are using the same window, you had 2250fc and 23micromol/m^2/s earlier. Now you have 4500fc and 260 micromoles/m^2/s. 2x difference in fc, but 12x difference in PPFD. What kind of PAR meter are you using?

Why don't you measure outside under direct sun when there is no cloud? You can calculate the expected PPFD using this calculator:

http://clearskycalculator.com/quantumsensor.htm

You can multiplied the calculated value by 5.01 to get the expected fc.


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## masaccio (Apr 11, 2019)

naoki said:


> Then your PAR meter is broken. I'm assuming that you are using the same window, you had 2250fc and 23micromol/m^2/s earlier. Now you have 4500fc and 260 micromoles/m^2/s. 2x difference in fc, but 12x difference in PPFD. What kind of PAR meter are you using?
> 
> Why don't you measure outside under direct sun when there is no cloud? You can calculate the expected PPFD using this calculator:
> 
> ...



I see what you mean. Just found the Apogee website that has conversion tables. I'm heading outside. Thanks.


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