LED lights and PAR w/ Paphs&Phrags

[shade131]

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

 

[Ray]

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

 

[southernbelle]

I have grown and bloomed my Phrags successfully under LED lights for about 5 years. I don’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...

 

[southernbelle]

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

 

[southernbelle]

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.

 

[TyroneGenade]

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

 

[xiphius]

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...

 

[Ray]

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:

 

[xiphius]

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:

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..."

 

[masaccio]

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.

 

[masaccio]

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.

 

[TyroneGenade]

... 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/ .

 

[southernbelle]

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/

 

[xiphius]

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).

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.

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.

 

[TyroneGenade]

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...

 

[xiphius]

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 .

 

[TyroneGenade]

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:

 

[masaccio]

Stunning!

 

[shade131]

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.

 

[Ray]

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.)