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Post by Apoplast on Oct 21, 2013 12:38:21 GMT
Hi Coline - Agreed. LED's are not cost effective in North America to replace fluorescents, and it sounds like that is also the case in Central America currently too. This is one of the things John covers in his new "how to" page for the ICPS. Apparently in Europe the cost of electricity is high enough that the difference in efficiencies can make it worth it. Here the cost differences can be made up for through decreased power consumption if you are using metal halide bulbs or high pressure sodium lights. The circular fixtures we tested are really best to replace these latter two types anyhow. We didn't have any tube LED's on hand to examine.
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Post by John Brittnacher on Oct 22, 2013 0:13:13 GMT
In order to learn about LEDs for the page on the ICPS web site I bought 5 different kinds of LED lights for use in my house. I do not like them at all for general lighting. The color that things appear under the lights is too unnatural. It is like the really old greenish fluorescent lights. The lights have a color rendering index of 80 to 82 but are nowhere near as good as 85 CRI 800 series phosphor fluorescents (such as Philips 54W/841 T5 HO/ALTO that Home Depot carries).
So how can 85 CRI fluorescents be so much better for home lighting compared to 82 CRI LEDs? We attend a lot of plays at the Oregon Shakespeare Festival and in the intimate Thomas Theater you can see light fixtures. When they want a brilliant white light that makes colors really pop, they use a combination of orange and blue lights. That is exactly what 800 series phosphor fluorescents use. Monet also explored this effect in his "pointillist" paintings but that is an even longer story. Why is this important for plants? I think 80 CRI LEDs have too much of their spectrum in the greens compared to newer fluorescents. So besides having a lumens per watt the same or worse than fluorescents, the light is not as useful to the plants either. Some day I will try a 95 CRI LED but at $50 they are a little pricy for what you get.
OK, so the topic here is "grow lights". Discrete colored LED grow lights are horribly expensive. Yes I would love to play with some but I do not think they are cost effective. Someone who has their plants in a basement needs to do some experiments, real experiments with controls, etc., to see exactly how bad (or good) LED grow lights are. And I don't mean TC plants like Wistuba's setup. TC plants do not require much light. I mean growing something that requires a lot light like Heliamphora. Until I can do the math with specifications and it comes out good or someone does an experiment showing LEDs are worth the cost, I am not going there.
There is one application where I love LEDs. For macrophotography I have a 5000K PAR30L LED spot light. I use it for primary lighting on a subject and 3 5000K CFLs in reflectors for fill and back lighting. The results are amazing.
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Post by Apoplast on Oct 22, 2013 3:42:37 GMT
Hi John - Thanks for weighing in directly! I certainly didn't want to be putting words in your mouth. I may give some experiments on color LED fixtures a whirl at some point in the future - but it sounds like I'd have to get some helis first.
I do have one picky, technical point. I've noticed most people, when speaking about lights for plants, talk in terms of "lumens" as a metric, which is weighted for human color sensitivity. It's not a great measure for plants. The measure typically used for plants is PAR (photosynthetically active radiation) - a measure of the light plants can use. I am pretty sure LED's with the narrower wavelengths produced bias PAR sensors a bit, but it's still a more directly plant relevant way to measure light. I'm sure there is a good reason people cling to lumens for grow lights, but I don't exactly know what it is. Is it just because household lights are labeled with lumens?
As a side note, I am also not familiar with CRI either, but that one sounds like it's associated with aesthetics more than anything else.
Okay, technical rant over. Back to your regularly scheduled plant discussions.
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taz6122
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Post by taz6122 on Oct 22, 2013 4:03:14 GMT
I do have one picky, technical point. I've noticed most people, when speaking about lights for plants, talk in terms of "lumens" as a metric, which is weighted for human color sensitivity. It's not a great measure for plants. The measure typically used for plants is PAR (photosynthetically active radiation) - a measure of the light plants can use. I am pretty sure LED's with the narrower wavelengths produced bias PAR sensors a bit, but it's still a more directly plant relevant way to measure light. I'm sure there is a good reason people cling to lumens for grow lights, but I don't exactly know what it is. Is it just because household lights are labeled with lumens? Probably because higher lumen bulbs (with peaks in the right spectrum's) are associated with better plant growth? At least that's been my experience when dealing with fluorescents. If PAR was displayed on the box I'm sure more would use it as a reference!
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Post by Apoplast on Oct 22, 2013 13:56:28 GMT
Hi Taz - Fair enough. I guess my gripe is largely with the companies selling grow lights.
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Post by John Brittnacher on Oct 22, 2013 17:54:50 GMT
Lumens vs. PAR is something we could argue for hours. I use lumens because that is a standard lighting measure. It is well defined and I know what I am dealing with. As I said on the general lighting web page, it measures exactly the wavelengths plants don't care about. So be it. That is why I also look at spectrum. The 841 phosphor fluorescents pump out a lot of light in the tails of the lumen curve compared to 80 CRI LEDs. I can do all the math I need in my head to see the advantage of the newer fluorescents at the same lumen ratings.
I don't consider PAR a standard and I do not think it is really what its name implies. If I understand correctly someone measured the light wavelengths intact leaves absorb. That is not the same as photosynthetically active. As I understand, and I may be wrong, all that matters is 660 nm deep read (or near infrared). The plant has to convert all the other wavelengths into that color. The conversion wastes a lot of energy. The only lighting source that doesn't have to convert UV or blue light to 660 nm is 660 nm red LEDs. However 660 nm LEDs are not as efficient as orange and blue LEDs at generating light. So the lighting sources are also wasting energy as well. It is all tradeoffs. That said, the plants do require white light to grow properly and spectrum does matter. We don't know what wavelengths are required or critical.
I think manufactures of HID plant lighting jumped on PAR because it justified their green-biased lamps. I can tell you from experience at UCDavis in the greenhouses that were shaded during the winter that the greenish lights were useless and the orange ones were great. Well, the plants looked better but many died under the green ones but they grew very well under the orange ones.
If you look at PAR meter specs all they are doing is using a different filter in front of the light sensor. That filter is more like an inverted U than an inverted V for lumens. What you want is an inverted W sensitivity curve with the peaks that correspond to the chlorophyll peaks. You do need some white light as well for plant health so it would be a mushy W. So the point here is PAR meters don't measure what they purport to measure. Maybe the expensive ones do but all the ones I checked didn't. All they did was add a little sensitivity on the blue and red tails.
As far as color rendering index (CRI), that is also a standard. There is a protocol where you measure color accuracy at various colors, put the numbers into a formula, and turn the crank. You can get 80 CRI an infinite number of ways with an infinite number of those giving terrible viewing accuracy. Again you have to look at the spectrum and the light yourself to understand what a lamp is doing.
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Post by Apoplast on Oct 24, 2013 13:55:42 GMT
Hi John - I completely agree that you and I could probably discuss lighting at length. What fun that would be! Maybe someday we'll have the chance to do so in person. Probably not worth trying in writing here.
There is one thing I would like to disagree with here because I don't want the wrong impression to be propagated. You said you don't consider PAR a standard. PAR is absolutely a standard measure of light in plant physiology, ecology, horticulture, agronomy, etc. Essentially anywhere people are trying to quantitatively assess a plant's capacity for photosynthesis under different light intensities they use PAR. However, your point that PAR is not as readily available for most lights nor is it easy to measure unless you buy specialized equipment is well taken. Regardless of the metric's availability to the average consumer, it remains the case that it is the measure plant available light. That's not to say it is an infallible or perfect measure. But it is still the current gold standard for a single metric of plant available light.
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coline
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Post by coline on Oct 25, 2013 0:25:25 GMT
Indeed John, other light wavelenght are normally "wasted" in heat in plant's processes, to convert them to the red wavelenght, but also, I don't remember it right away. but also, blue light has an important factor for the plants, it is the light with enough energy to do some precise processes, not photosynthesis, that is why plants use it. Also, on a brief explanation on space trips that I had in USS united space school in Houston, plants that were grown in red light, in the case of crops, where the ones with the better yields since they did not offshoot in lateral growth points.
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Post by John Brittnacher on Oct 28, 2013 17:27:01 GMT
I have been convinced off-forum that PAR is a standard and an interesting one. It is essentially a measure of photon numbers in the range of 400 to 700 nm where a 400 nm photo counts the same as a 700 nm photon. An important distinction between lux and PAR is lux is a measure of energy. Lower wavelength light has higher energy per photon so for lux a 400 nm photon would count more than a 700 nm photon (actually they would both count almost zero for lux because of the luminosity function).
I still believe PAR is a misnomer. But it is better as a measure of light for plants than lux. And it is a much better measure for scientific studies.
That said, it is much harder to build a PAR meter than to build a lux meter. You can buy a decent lux meter for $35. A $35 PAR meter is essentially a lux meter with a filter biasing the response toward the red end. The one I have seen the response curve for cuts off at 660 nm. The industry standard PAR meter used by scientists costs $1200.
It would be interesting to compare lux and PAR measurement between different types of lighting.
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Post by ICPS-bob on Oct 28, 2013 23:36:30 GMT
An interesting web page is at www.lumigrow.com/demystifying-lumens-lux-par/With the following conclusions: But, then, do all species of CP respond to the same wavelengths? And, is there an optimum "brightness" (or amount of energy) for each species of CP? -- A great thesis topic.
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Post by Apoplast on Oct 29, 2013 22:34:06 GMT
Hi Bob - Thanks for posting the link, it was an interesting read! I agree and disagree with the assessment on the website. It's an intriguing approach, and were their products quite a bit cheaper I'd be interested in getting one of their LED fixtures to play with.
Back to the topic at hand. I agree that knowing the intensity of light across the PAR spectrum is useful. But if we are going to collapse the plant usable light to a single metric, it keeps coming back to PAR, or something functionally equivalent. Though no single metric will perfectly describe the number of photos a specific plant is utilizing under all conditions (especially as we have greater control of the exact wavelengths we are providing), the advantages of a single metric are highlighted in your proposal for a master's thesis.
Once we start trying to dial into ideal spectra for different species, the picture rapidly becomes complex. Not only are there numerous species of plants people like to grow under lights, which may each have different spectral optima, everyone of these species is going to have plastic responses to light availability. These plastic responses are what allows plants to cope with a range of light availability, and likely means the the clean single optima doesn't exist for a species outside of a particular developmental regime or acclimation condition.
To avoid all of this, the fuzziness associated with a single metric like PAR allows us to generally assess whether a plant will get more usable light under a given set of conditions or not. And, I think the best support for my argument at the moment is that the company's website with the discussion still discusses their output in PAR, though they do post the spectroradiometric graph of their greenhouse lights in addition to using PAR.
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Green Hornet
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Post by Green Hornet on Jul 18, 2015 16:46:42 GMT
Wow. Forgot I started this thread... when? Damn! I was away from ICPS for a few years. Sorry 'bout that. Been growing Neps and loving it all this time, but long ago abandoned LED lights. Now they live in the same closet as my collection of laserdiscs and jalapeno patio lights. In retrospect, they do work, but are really quite single purposed. They grow plants. Having said that, for Neps, they make staring at your plants (as I have spent untold hours doing over many years) less satisfactory than looking at a good black & white photo of those same plants. I've gone completely to full spectrum T-5's now. They, in many ways, are the best lights I've ever used. I like experimenting with new things, but (a few dead plants later) you always come back to the ones that actually work. In that respect, T-8's still do the trick for rooting cuttings in a 55 gallon tank, though I use T-5's for that too. In my 150 gallon tall tanks, nothing less will do. Thanks to all who responded! This long after the last post here, I'm pretty sure I'm talking to myself, but it's neither the first or last time and thanks, just the same.
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Post by southbaytraps on Sept 6, 2015 1:03:06 GMT
I have tried almost every brand of LED's and highly suggest Kind LED's if you have the cash. You can't compare growth rates or coloration of a plant grown under one of these to T5's or any other LED that I have tested. Flytraps, Heliamphora, and Cephs all love them. I have enough of these that I wasn't afraid of burning a plant or two while testing. After having very good success with all of those, I was tempted to stick some highlanders and seed grown nepenthes under one but was cautious since you can fry a hamata in a few hours.... So I prepped two plug trays of Ventrata's, one was placed under a 8 bulb T5 system, the other was placed under a Kind XL750... The results were pretty much what I expected, except leaf growth was very similar between the LED's and T5's. Pitcher production on the other hand can't be compared at all. I wish I had done a before/after sort of thing but I was primarily documenting this for myself. The length of time was only 14 days, at which point the plants under the led's began to show signs of stress but only because they were not potted adequately. My current setup uses Kinds Veg light for highlands, 1cm seedlings etc... I still use the XL750 and place it in mother earth mode. Note: I only sell products on my website if I have tested them and had good results. Other than T5's these are the only LED's I recommend. I'm not allowed to advertise lower than retail prices, but icps members etc are more than welcome to email. Do your homework, I'm not looking for sales but if you end up with one then at least i can save you a few bucks. Okay Top Picture is a plug tray of Ventrata's which were placed under T5's for 14 days with no nutrients or foliar sprays Here is the same variety. Under after 14 days under a Kind LED. Notice pitcher production and size is substantially better. Leaves remain about the same size! ... This was due to the lighting spectrum I had setup which had a good mix but was very high in the red spectrum If you are skeptical, I can do a more controlled experiment but there are plenty of members who use these LED's now and swear by them. Price tag is high, wattage used is low, performance is much better than T5's. They are long term investments. ~Mike | Southbay
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coline
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Post by coline on Sept 6, 2015 14:02:55 GMT
During these past years I had finally seen some differences and tries, I have switched completely to LEDs in a slow basis as all my CFLs were burning out, and I have placed a highland collection of helis and neps under LED lights, I use one warm colored led and 2 white ones at 20cm, and plants are responding very well, new pitchers on the way. The only thing I did (since it is the only I may measure) is to choose the led with the highest lumen/Watt ratio, in my case almost 80% (80l/1W). Even plants coming out from TC on a cheap leds I bought with no lumen measure, just 5Watt power grow well and making pitchers, just that in a full green color which corrects when they go to a greenhouse.
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Post by Kgrizzlefoshizzle on Oct 23, 2015 23:57:53 GMT
I just purchased a lightimetunnel 300w Led light ballast... I'm trying to figure out the proper distance between the fixture and the plants.. I have cephs and drosera ... Any input?
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