Question about these lights I found. They are 1.5W LED bulbs with a 6500K temperature rating. About 8 dollars and carried in the hardware shop down the street, I would love it if these lights actually did something useful for my plants. So I did a little reading on the relation of Color Temperature and the wavelength of emitted light. Found Wien's Displacement Law (wikipedia):

λ = ≈3,000,000 nmK/T

where λ is the wavelength of peak intensity, and T is the color temperature the black body in Kelvin.

A little more reading on other sites (sources below for verification) indicated that this law holds true for solid state lighting, and, therefore, LEDs.

Working this equation through (using the more accurate 2,897,769 instead of 3 million) with 6500K, leads to a wavelength of 445nm. Since LEDs emit only select wavelengths, I assume that this bulb would only emit 445nm light (or right around there).

And since 445nm light is great for plants in vegging, I think these lights would provide great supplement lighting.

Any comments on my reasoning? Or has anyone tried these out before?

Thanks.

Souces:
SOLID STATE LIGHTING DEVICES AND METHODS OF MANUFACTURING THE SAME - Patent application
"This occurs because the wavelength associated with the peak radiation of the blackbody radiator becomes progressively shorter with increased temperature, consistent with the Wien Displacement Law. Illuminants which produce light which is on or near the blackbody locus can thus be described in terms of their color temperature."

LED Light Knowledge - Suzhou Neopower Electronic Co., Ltd.
Under a section titled "Technical Parameters for LED Light":
"Color temperature is a characteristic of visible light that has important applications in lighting, photography, videography, publishing, and other fields. The color temperature of a light sources is determined by comparing its chromaticity with that of an ideal black-body radiator. The temperature, usually measured in kelvins(K) at which the heated black-body radiator matches the color of the light source is that source's color temperature, for a black body source, it is directly related to Planck's law and Wien's displacement law."

LED*Waves LED Blog: Doctor, my color has a temperature!
"The future of video and still photography undoubtedly belongs to digital equipment with solid-state lighting (LEDs and OLEDs). This allows for precise control of color temperature and uses a fraction of the power of regular instruments."

Attached Images

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	Ledzoom.JPG (105.6 KB, 3 views)

Lights of America has a very bad reputation afaik. Check Amazon reviews of their products, and Costco just issued a voluntary recall on some of their stuff.

Well the reviews all complain about the lights not being bright enough to use as household lighting. I do agree these lights aren't great for lighting lamps (because LEDs are directional and point light up, not out, which is what the complaints were about). If i point these directly at my plants, all light will be directed onto the plant (another reason LEDs are very efficient).

I want to know if this light is good for the plant. I know people don't like these lights for their houses but they may be great for plants.

I moved this to the Growing with LEDs section. Good luck!

__________________
My first grow! Check it out! (Perpetual Round Two! Starting at post #61)

Cannabis is a transformation, f(x), such that -> and -> . Do the math and smoke!

at 8 dollars per 1.5watt its insanely expensive.

Not really. With LEDs you don't need 1000W of input. With HID lights such as Metal Halide and Hi-Pressure Sodium, only 30% to 40% of the energy going in is actually making light. The rest is 600W worth of wasted electricity. LEDs can emit up to 90% of their incoming energy as light if they are kept cool enough.

Plus most light sources emit a broad spectrum of wavelengths and not all of these are needed for plant growth, only some. The reason HIDs are great if you're choosing one or few lights is because they hit all points of the spectrum that plants do want. They're just too hot for what I need them for right now.

I really just want to know if the light coming out of the bulb is good for plant growth based on the reasoning in the first post.

Because if the light is good, a board with 12W worth of these with come CFLs in the red region will fit nicely on the top shelf in my closet. Mainly for starting younger plants in a small space. Lots of light and little heat (too many lights in my closet already lol) That's the only reason I would bother with these.

But if anyone has any input on the emitted light I would greatly appreciate it. I don't want to skip over these bulbs if my plants will like them because they work perfectly for my needs.

Actually HPS are more efficient, watt for watt.


If all the LEDs are emitting the same wavelength, then I suspect you are correct on the wavelength. You should be able to find equivalent or better LEDs for cheaper though imo.

Now heres a question in line with the thread I posted.Am I incorrect when I state that hps= 140 lm/watt, and the very best leds produce 100 lm/watt?Now I've read that with led's we have to "forget lumens", but recently I've read that HydroGrow led is putting out a "pro" model with a jacked up lumen rating.So, that was kinda confusing.I'm just trying to make a relatively accurate watt/watt comparison based on fact, not hype.I mean, how much led power is required to replace 400 watts of hid, with the same effective footprint as the 400.And with leds producing less lm/watt than hps, then...that would make led's less efficient, thereby producing even more heat than hps...watt per watt of course.It's just that theres so much conflicting info with these things.All the info seems to come from the people selling them.

There are some LED's with over 200lm/W.

Wow! 200 lm/watt-that's freakin nuts.How much would it cost to build a unit with those bad boys?I've seen some sick homebrew units- 15-20 watt diodes, but now I'm reading that 1w diodes are more effective?Any truth to that?Because that'll just screw my head up completely.I figured, with my limited knowledge, that it only stands to reason that the higher the diode wattage, the higher the intensity-the better your results.I've seen grows with one of those 45 watt glow panels, and that grow didnt even come close to a 50 watt(the little halfy ufo's) grow I saw posted.I figured the trend would just continue.

I might have misread a spec sheet. I thought I saw one that had 200 lm/w but here are some that are close.

Here are the latest Cree's that are pushing 105 lm/W and can run at 3W for around $5.
Cutter Electronics

Here is a Z-Power at 90 lm/W with a total output of 900 lm!!! They are $28 each though.
Seoul Semiconductor, Inc

The Cree XP-G R5 can reach up to 160 lm/W but only at lower power usage so you will not actually output 160lm at one watt.

Here is an interesting image I found that shows the different LED bins and their total lm output.

Aren't lumens a measure of visible light?

And doesn't most visible light consist of colors plants have little use for (especially in bloom)?

Lumens are only good for standard lighting in visible wavelengths. It's a great way to tell how bright a light will make a room. But, it's less than ideal for LED grow lights.

__________________
-Michael

Now heres where the two camps apparently split, and this is where it gets interesting for me.It seems, from the sea of literature I've navigated through, that the intensity of the diode is determined by the viewing angle, is this correct?But then, I've seen threads turn into downtown Beirut when this subject arises.Theres another led developer-Hydrogrowled that has stated that she's putting out a unit with a higher lumen count.I was gonna ask her why, but I've seen her rip into other members for asking a simple question.Now, I know that you simply cannot divulge any info that pertains to Prosources RnD, but I dont see you guys breaking a sweat over lumens.Could it be possible that they are now adding these unnessesary lumens to kind of "cheat" their units into higher performance range.I mean this person,hydrogrow, is boasting 2g/ watt.Is that even possible.Sorry about the barrage of questions Michael, but you know how crazy this led has gotten...and you havent blasted me yet lol jk.I'm just trying to wrap my head around all this, and seperate fact from fiction.I appreciate your time man

Actually, our position is that lumens are irrelevant and the term is only used as a sales tactic. As I said, lumens refer to visible light. Plants don't care about how the human eye perceives light. It's that simple.

As an aside, HydroGrowLED has serious issues on many, many levels. I feel sorry for anyone carrying around that much rage. It's a shame, really.

For whatever it's worth, here's our slant on things. A lot of LED light makers make a lot of wild claims. But, no one backs their product with a guarantee you can trust. So, we decided to forget about making wild claims and simply offer our customers the assurance that, if they don't like our lights, they have 90 days to return them for a full refund. Very few people have taken us up on that offer.

From the customer's perspective, the only thing that matters is that the product does what we say it will do. When people buy an iPhone from Apple, do they expect Apple to supply a complete schematic and all the specs for the design - or do they just want it to work? Why should grow lights be any different?

__________________
-Michael

Interesting thread, I thought I'd add the best read I 've found so far, on breaking lighting info into digestible nuggets... We can't leave this subject just to you rocket scientists guys...lol.

For those with no patience...
Lumens is a measurement of Illumination...
Foot-candles is a measurement of Radiation...

Category: LED Technical Information

Lumens, Illuminance, Foot-candles and bright shiny beads….


In defining how bright something is, we have two things to consider.

1. How bright it is at the source- How Bright is that light?
2. How much light is falling on something a certain distance away from the light.

Lets' do some definitions now……

We're in America, so we are going to talk about units of measurement that concern distance in feet and inches. So, we will use some terms that folks in Europe don't use. We're going to talk about "foot-candles".

This one's simple. Get a birthday cake candle. Get a ruler. Stick the candle on one end of the ruler. Light the candle. Turn out the lights. Sing Happy Birthday to Doc. It was his 47th on the 23rd. OK, quiet down. Enough of that nonsense. One foot-candle of light is the amount of light that birthday cake candle generates one foot away.

That's a neat unit of measurement. Why? Say you have a lamp. You are told it produces 100 foot candles of light. That means at one foot from the lamp, you will receive 100 foot candles of light.

But here's where it gets tricky. The further away you move the light from what you want to illuminate, the less bright the light seems! If you measure it at the light, it's just as bright. But when you measure at the object you want illuminated, there is less light! A Physics teacher is going to tell you that light measured on an object is INVERSELY PROPORTIONAL to the distance the object is from the light source. That's a very scientific and math rich way of saying, the closer you are to the light bulb, the brighter that bulb is. Or, think of it this way. You can't change how much light comes out of your light bulb. So, to make more light on an object, you have to either move the light closer, or add more lights.

Now, lets get to LUMENS.

A LUMEN is a unit of measurement of light. It measures light much the same way. Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light! A LUMEN is equal to one foot-candle falling on one square foot of area.

So, if we take your candle and ruler, lets place a book at the opposite end from the candle. We'd have a bit of a light up if we put the book right next to the candle, you know. If that book happens to be one foot by one foot, it's one square foot. Ok, got the math done there. Now, all the light falling on that book, one foot away from your candle equals both…….1 foot candle AND one LUMEN!

Ahh, we've confused you. Let's split off from this and talk about the difference between RADIANCE and ILLUMINANCE.

RADIANCE is another way of saying how much energy is released from that light source. Again, you measure it at the source. Unless you're talking about measuring the radiance of something intensely hot, like the Sun. Then you might want to measure it at night, when it's off.

ILLUMINANCE is what results from the use of light. You turn your flashlight on in a dark room, and you light something up. That's ILLUMINANCE. Turning on a light in a dark room to make the burglar visible gives you ILLUMINANCE. It also gives you another problem when you note the burglar is pointing your duck gun at your bellybutton.

Illuminance is the intensity or degree to which something is illuminated and is therefore not the amount of light produced by the light source. This is measured in foot-candles again! And when people talk about LUX, it's illuminance measured in metric units rather than English units of measure. To reinforce that, LUX is the measurement of actual light available at a given distance. A lux equals one lumen incident per square meter of illuminated surface area. They're measuring the same thing, just using different measurement units.

Pretend you're an old photographer, like O. Winston Link, or Ansel Adams. These two gods of black and white photography (and a print made by either can fetch quite a hefty sum of money these days) used a device called a light meter to help them judge their exposure. (There is another way of judging exposure-that's when someone whispers in our ear at a cocktail party, "You silly twit, your fly's come undone!").

These light meters were nifty devices. You could use it to show how much light was falling on an object, light from the sun, and reflected light energy from every thing else. Or you could use it to show how much light energy was reflected off the object itself.

All this brings back two points. Well, three.

The first point is if we measure the output of a light at the source that gives us one thing.

The second point is that we use an entirely different unit of measure if we are measuring the results of that light's output.

The third point is the instructor is right off his trolley, isn't he?

Now back to the book at the end of the ruler.

We've measured two different things. We have a unit of measure for how much light is produced. We Yankees express that as a foot-candle. Being lazy, we use it all over the
place.

More Confusion! Candlepower!

Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight. Is it a measure of how much light falls upon an object some distance away? No. That's illuminance. Is it a measure of how well we see an object that is illuminated by that light source? No. That's something all together different, and we are not going there!

Nowadays we use the term CANDELA instead of candlepower. Candlepower, or CANDELA is a measure of how much light the bulb produces, measured at the bulb, rather than how much falls upon the thing you want to light up. Further confusing the matter is beam focus. That's how much candlepower can be focused using a reflector/lens assembly. Obviously, if you project all your light bulbs intensity at a given spot, or towards something, it will be more intense, and the illuminance will be higher.

And here comes the confuser! A candlepower as a unit of measure is not the same as a foot-candle. A candlepower is a measurement of the light at the source, not at the object you light up.

And a candela is the metric equivalent of the light output of that one candle, based on metric calculations. And since using a candle is rather imprecise, the definition was amended to replace a light source using carbon filaments with a very specific light source, see the following:
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

The above from the National Institute of Standards Reference on Constants, Units, and Uncertainty.

Candlepower is a measure of light taken at the source-not at the target. Foot-candles tell us how much of that light is directed at an object we want to illuminate.

Now, lets convert the lumens, a metric unit of light measurement, to candlepower.

We understand a candle radiates light equally in all directions, its output, in this consideration is not focused by any mechanical means (lenses or reflectors). Pretend for a moment that a transparent sphere one meter in radius surrounds your candle. We know that there are 12.57 square meters of surface area in such a sphere. Remember your Solid Geometry classes?

That one candle (1 Candlepower/Candela) is illuminating equally the entire surface of that sphere. The amount of light energy then reflected from that surface is defined thusly:

The amount of energy emanating from one square meter of surface is one lumen. And if we decrease the size of the sphere to one foot radius, we increase the reflected energy 12.57 times of that which fell on the square meter area.

LUX is an abbreviation for Lumens per square meter.
Foot-candles equal the amount of Lumens per square feet of area.

So, that one candlepower equivalent equals 12.57 lumens.

And for you figuring out LED equivalents, first you must know how many lumens your LED's each produce. Then divide that value by 12.57 and you have candlepower of the LED. You don't have foot-candles, remember foot-candles are illuminance. And we are measuring radiance.

Summing it all up:

Candlepower is a rating of light output at the source, using English measurements.
Foot-candles are a measurement of light at an illuminated object.
Lumens are a metric equivalent to foot-candles in that they are measured at an object you want to illuminate.
Divide the number of lumens you have produced, or are capable of producing, by 12.57 and you get the candlepower equivalent of that light source.

We've now converted a measurement taken some distance from the illuminated object, converted it from a metric standard to an English unit of measure, and further converted it from a measure of illumination to a measure of radiation!

The key to all that is here:
The thing is, we use wavelengths that aren't visible, or are hardly visible, to humans.

So, illuminating an object means what, precisely? Making it visible, maybe? To humans, even? That's what I mean when I say that measuring the power to illuminate is not really ideal for measuring the effectiveness of a grow light. Illuminating an object and growing bud are two entirely different missions with two entirely different parameters and requirements.

That kinda throws everything out of whack, I think, and makes lumens/candlepower/foot-candles irrelevant.

__________________
-Michael

WOW!! You guys have stoked the fires here.I'm going to take some time here to digest all of this.Then I'm going to bother you guys again lol.It's apparent that a lack of knowledge on my part has caused a mish-mashing of all these terms.Thanks for getting me on track here.

[B]The thing is, we use wavelengths that aren't visible, or are hardly visible, to humans.

So, illuminating an object means what, precisely? Making it visible, maybe? To humans, even? That's what I mean when I say that measuring the power to illuminate is not really ideal for measuring the effectiveness of a grow light. Illuminating an object and growing bud are two entirely different missions with two entirely different parameters and requirements.

That kinda throws everything out of whack, I think, and makes lumens/candlepower/foot-candles irrelevant./B]

I might have this wrong but, the author explains that regardless of the part of the spectrum involved, all light is a measurable energy and can be quantified at the source and also at any point where it is interrupted by an object. I have no problem understanding that Brightness has no bearing on this discussion but, I think the author clearly states that Radiation is... the power of any type of light, measurable as energy in the unit of Foot-candles... To me, he saying the radiative effect of a led array is the compelling issue since distance is so critical in performance. Again, IMO... that's no different then knowing a 1000w HPS reaches further down a plant, then a 250 hps... that's Radiation not Illumination at work...

Yeah, I think we're thinking along different lines. I see what you're saying now.

__________________
-Michael

Where these conversations normally fall apart, is when people start mixing the Biology and the Physics of Led lights... Two way different disciplines and actually I am totally intrigued by the subject so, I'm just having fun with the learning curve...