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Added 15,600 lumens of 2700K light

AJ,

I "think" by definition, it is one foot away, as far as how bulbs are quoted. The official definition is one foot.

It was a movie, so I'm sure there were liberties taken, but it showed an indoor growing room of a pot producer - he had grow lights going north and south as well as eat and west.

To be honest, I don't think this has much application on growing plantings, as they are not likely to be more than six-eight inches tall. But for me, I have to consider this if I want to grow plants to maturity, and especially get fruit. I'm trying to figure out if mirrors will work or if painting the walls with glossy white paint will deflect light to the bottom part of the plant.

Here's my envisioned set-up: a 15 foot length of space that will be two feet wide. Two rows of 14 lights (probably 20-23 Wattt, 2700K CFL lights unless Omri convinces me otherwise) staggered. This should give me enough room to grow about seven plants, four tomatoes, two peppers and an eggplant.

I may need to build "doors" on the front that so the light will be reflected. But that can wait.

Mike
 
Looooong post...

Here is my simplistic idea of lighting from all the reading I have done...yes, Omri, I have read your site and the information is good..I have read a lot of that on other sites too and here on THP......and Mike, you are the reason I went and got the 2700K bulbs.....
Plants use light....yes?
OK...do they use all of it or just some of it? They only use a few bands of the spectrum (fairly broad in my opinion) for growing/flowering/fruiting. These different plant stages definitely use some of the light from each bulbs spectrum it produces but some stages do better with more of a certain band of the spectrum. That is where we come into "color". I don't pay attention to the warm white, cool white, etc. What I look for on the packaging is the color temperature rating of the light...that’s where you get your different bands of light from. If you use different color temperatures of light, you are getting a different spectrum with some bands stronger than others. I am assuming, although I have no proof of it, that the spectrum of light emitted by the bulbs is somewhat skewed to the color temperature it is rated at such as the 6500K, 4100K, and 2700K bulbs I am using. OK...not gonna get to light strength yet, going to continue with the color spectrum saga. As I said simplistically, each different color temperature light emits a spectrum that is skewed towards the temperature of the bulb. If you choose a bulb temperature close to the colors the plants use during their growing cycle, you could improve on the efficiency of both growth and light usage. The 2700K bulb is down on the red end of the spectrum with the 6500K being more on the blue end. The 4100K is more red than blue (IMHO). Therefore you have three different light sources that emit three differently biased spectrums. Mixing those spectrums is what gives you the benefit of improving the efficiency of the plant to produce the different chlorophylls since you are dialing in on the bands of the spectrum the plants use. What I have said has to be absolutely true. If I am wrong, tell me, but don't just tell me I am wrong, please tell me where to find out where I am wrong and where I can learn the "right" way for indoor grow-lighting.
I am not going into what bands of the spectrum the plants use because there is a lot of information all saying the same thing.....vegetative state...blue band of the spectrum has more benefit and the red band of the spectrum is better for flowering/fruiting. But the plant cannot exist on a single narrow band of light from the spectrum.
OK, with that said, time for intensity. Each light bulb has an intensity level. That intensity level is categorized as lumens. The power the bulb uses is Watts. Watts don't mean squat to color...period. Both of these ratings for the bulb are on the packaging...keep at least one of the empty packages for reference because all this information us normally NOT on the bulbs...I have started writing on my bulbs their temperature rating with a magic marker when I install them. The more watts, the more lumens the bulb emits that is another fact...period. This is where it gets interesting...mixing lumens and color temperature....I would like to be able to produce a spectrum that is biased toward the red end and blue end that also produces enough penetration to get at least 2 1/2 feet (~76cm) below the light with enough intensity to do the lower leaves of the plants some good. When a source says 100 lumens per square foot, they are talking at the surface of that square foot...as GB mentioned, as the distance increases by the foot, 4 times as much luminescence is required to produce the same at the surface as was required fat the surface. Like this, at one foot, the surface receives 100 lumens of light (remember, we already have chosen our spectral band selection), at 2 feet it would take 400 lumens emitted to get 100 at the surface, at 3 feet it takes 900 lumens, etc. Pure theoretical science and remember, this is per square foot, so if I want to produce 100 lumens/sq foot at the surface 3 feet below, I will have to provide 900 lumens total for that square foot. My grow box is 16 sq feet and for 100 lumens/sq foot I would need 5400 lumens/sq ft 3 feet above. As I said earlier, I am producing 40K/16 sq ft lumens from above and that is giving me 277 lumens per square foot (at 100% efficiency) three feet below but at 2 feet down, I am getting 625 lumens per square foot. Now what you have to determine is how many lumens of each spectral band the plant uses that makes it grow best at the different stages of its life. That's where the real research needs to be directed.
I am currently producing right at 40K lumens within an inch of a 4X4 plane (call it the top plane) across my grow box. That plane is perpendicular to the bottom of the box that is about 4 feet away. The bottom leaves are only about 2 1/2' below the lights therefore, I am providing a plane perpendicular to the light source with about 450 lumens/sq ft.
Are my thoughts incorrect on this?
 
AJ,

I pretty much agree with everything, or at lest close to. Some bulbs do produce more lumens per watt than others - I've seen 20 watt CFLs that are listed from 900-1200 lumens even though they are in the same light spectrum. I also thought, and GB pointed it out, that lumens are halved for every foot light travels, meaning that you would need 200 lumens to cover a square foot two feet from the source but only 100 lumens one foot away (400 lumens three feet deep, 800 lumens four feet away, etc.)

From what I read, sunlight is rated at 32,000-100,000 Lux (lumens per sq. meter) but I also read that on a bright, blue sky day, only about 5 percent of the sunlight is actually used by plants. If this is true, that translates into 1,600-5000 lux (or lumens per sq/me.) of PAR light.

Mike
 
AJ - not sure what you mean by 100% efficiency but other then that you're gettin' there... not totally sure about your math tho, but it's early yet and that was a long post (where are those ADD meds....) i'll read it again when i get back from school. btw, just thought of something, are your plants getting enough CO2?

WW - lux is metre candles, (as opposed to foot candles, lumens) 1 lumen = 10 lux. i have a diagram somewhere that'll show you what i meant, it's not always as intuitive as it sounds. i've heard sunlight is 5000 lumens per square foot, btw.
 
didn't really check my math and it may be wrong..don't have time to check it now...

yes, getting enough CO2 leaving grow box open all the time now...and running fan about an hour in the morning and at least that long in the evening.
 
Found this somewhere else... thought it was interesting...


Lumens is not the important thing, 10,000 lumens at one foot has a totally different penetration to 10,000 lumens at one inch. Light from a point source falls off inversely with the square of the distance. That means that the few inches from the top of a plant to the bottom makes a huge difference for a close light source and a small difference for a distant light source. How bright they are doesn't matter. 120,000 Lumens WILL not penetrate the same as 68,000 Lumens This totally meaningless statement compounds the problem. You need to be talking in terms of light intensity, measured in lux or foot-candles, which means you need to know the distance from the light source. 120,000 lumens at the same distance as 68,000 lumens will decrease in light intensity from top to bottom of the plant in exactly the same way, and will be nearly twice as intense at both the top and the bottom of the plant. The improved penetration becomes apparent when you place the 120,000 lumen source further away. For example, 120,000 lumens at three feet from the top of a two-foot plant produces a lower light intensity at the top of the plant and a higher light intensity at the bottom of the plant than the 68,000 lumen source place two feet from the top of the plant.

Unfortunately PAR watts doesn't measure the energy that the bulb puts off which the plants use for photosynthesis and growth. It measures the energy that the bulb actually puts off as visible light, actually any light 400nm-700nm.
Plants use different wavelengths of light with different efficiencies. Red light is used with 2-5 times the efficiency of green light, but all wavelengths are treated equally when measuring PAR watts. This can be considered an improvement on lumens which count green light more than red light.

Also, plants use photons, not watts. Plant scientists use a PAR measure that actually counts photons. This is important because it takes 700W to make the same number of blue photons as you get from 400W with red photons but one blue photon makes the same contribution to creating sugar as one red photon (ignoring the other stuff that blue photons do like making leaves follow the light). So a 400 PAR watts bulb may be putting out exactly the same number of photons as a 700 PAR watt bulb. The makers of metal halide lamps love this measure because it makes their lamps look better relative to HPS bulbs. The metal halide bulb converts about as much energy into light as an HPS bulb, but creates fewer photons because they are bluer and each photon takes more energy.

So PAR watts are just another flawed measure, maybe a little less flawed than lumens, but also less useful because it is only published for a few lamps and the published numbers are difficult to verify.
 
I got my light meter today so I had to do some checking. My germinator, a 20 inch by 30 inch box, rates at 1660 lux where the seedlings sprout. Under my 4' fluro lights, the rating is about 1140 lux at the top of the plants.

With the CFL lights, it's 100% PAR light, meaning it has as many PAR lux arriving at the plant as minimal sunlight (but significantly more than a completely cloudy day) But if it is a cloudless, bright sunny day in summer, I'm delivering about 1/3 the useful light the sun does.

Mike
 
I've got several plants that have just sprouted and hopefully another 100 popping up in the next day or two and I need to get them growing quickly - frost free day is just a month away. Replaced four 13 watt CFL with 23 watts and checked their Lux. The others were 5000K, these are 2700. Got a decent deal on them too - 5 bulbs for $22.50, including tax.

My light meter shows 7700 Lux at the top of the tray of seeds. It only measures light in the 430-700 nm. By comparison, the late afternoon sun on a fairly bright day (but not yet summer!) is 9200 Lux.

Mike
 
wordwiz said:
I got my light meter today so I had to do some checking. My germinator, a 20 inch by 30 inch box, rates at 1660 lux where the seedlings sprout. Under my 4' fluro lights, the rating is about 1140 lux at the top of the plants.

With the CFL lights, it's 100% PAR light, meaning it has as many PAR lux arriving at the plant as minimal sunlight (but significantly more than a completely cloudy day) But if it is a cloudless, bright sunny day in summer, I'm delivering about 1/3 the useful light the sun does.

Mike
Click to expand...

Hey Mike,

Where do you get such a meter, and how much does it cost?
 
DrHavanger said:
Hey Mike,

Where do you get such a meter, and how much does it cost?
Click to expand...
It's just a way to measure luminous intensity. really unnecessary when growing with artificial lights, because the light is usually placed right on top of the plant. you measure luminous intensity over a large distance.
Anyway, there's a minimum luminous intensity needed for the plant to grow healthy and anything more won't really do any change.
The luminous intensity level on an average sunny day is 66,000Lux (66Kilolux), and there's no way in hell you can achieve it. you don't need to.
What really matters is the wavelengths the plant gets. that's what translated into energy, not luminous intensity.
 
Omri said:
It's just a way to measure luminous intensity. really unnecessary when growing with artificial lights, because the light is usually placed right on top of the plant. you measure luminous intensity over a large distance.
Anyway, there's a minimum luminous intensity needed for the plant to grow healthy and anything more won't really do any change.
The luminous intensity level on an average sunny day is 66,000Lux (66Kilolux), and there's no way in hell you can achieve it. you don't need to.
What really matters is the wavelengths the plant gets. that's what translated into energy, not luminous intensity.
Click to expand...

That's interesting. Do you have a link that goes more into the wavelength information?
 
DrHavanger said:
:banghead:i've seen your website before, i should have know to check it out.:doh:
Click to expand...
Ha! see? it has its uses. ;)
It'll be updated soon. you can just use the RSS feeds for updates.
 
Omri said:
It's just a way to measure luminous intensity. really unnecessary when growing with artificial lights, because the light is usually placed right on top of the plant. you measure luminous intensity over a large distance.
Anyway, there's a minimum luminous intensity needed for the plant to grow healthy and anything more won't really do any change.
The luminous intensity level on an average sunny day is 66,000Lux (66Kilolux), and there's no way in hell you can achieve it. you don't need to.
What really matters is the wavelengths the plant gets. that's what translated into energy, not luminous intensity.
Click to expand...

Omri,

I think I posted this idea a long time ago. Yes, plants use light in the 430-700 nm spectrun for photosynthetic activity, thus giving rise to the PAR moniker.

Light from the sun varies from 32,000 - 127,000 Lux, depending on the sun's position, cloud cover, etc. But that Lux measures all wavelengths, not the PAR range. Some respectable sites suggest that only 5 percent of sunlight is PAR light, at least on an average day. I tend to think it is double that, maybe higher, but then I'm not an expert in this field nor one who has spent a lifetime studying it.

Perhaps my experiment will shed some light (no pun intended) on this discussion. I have two potatoes planted in the same type of soil, one under 13 Watt 5000K lights and the other under 13 watt 2700K lights. The former is kicking the latter's butt as far as plant growth is concerned - 10 inches to 4 at this time. But the proof will be in the harvest.

My lights are NOT placed on top of the plants - the CFLs put out too much heat to do this. They are, at this time, about eight inches from the top of the seed tray, which is where the measurement was taken.

At this point in time, I'm not interested in growing tall plants but rather ones I can plant one month from now and they will take off quickly.

Mike
 
Measuring PAR is mostly BS. MOSTLY, because there's no distinction of the different wavelengths. different wavelengths play different parts.

I can't see how a test of 5000K vs. 2700K will help in any way. there's no way to know what wavelengths those specific bulbs produce without checking the actual output. the fact one is more red, doesn't mean a thing. both use multiple types of wavelengths to produce the final color, and each bulb is different.

The fact is, there's nothing to prove. plants need certain wavelengths to grow, and we need enough luminous intensity so they'll get them. giving them too much of the wrong or even not efficient ones, won't do any help.

.
.
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Not saying your plants won't grow, just that you're not focusing on the right thing. you do well, but you can do better.
 
wordwiz said:
Ungrumpy Bear,

I thought that was the ratio but wasn't sure. That's why the intensity of sunlight is the same at the top of a five foot plant as the bottom - it has already travelled 93 million miles so that extra 60 inches make no difference!

Mike
Click to expand...

so the farther the light is kept away is the less it costs you to move it a few inches :)

lumens is a brightness to eyeballs rating
no point worrying about the curves- just test the lights you can buy- there are many less variables that way.
The photosynthetic peaks (which are not the same as lumen peaks) do not give complete spectrum (as shown with red-blue led)
So getting into 'micro einsteins' which is a way to say how much of each color of the rainbow is emitted in photos per second per light does not matter because man kind has not made a graph of the light spectrum to plant needs over the plant cycle.

The cool cool thing is they are all suffering at greenpinelane.com forum making LED lights with various leds.
Still though- there is only about 7 colors of 1w leds---
oh sorry to go on about LED :)
 
LEDs are cute idea for small plants. I'm actually working on a portable mini-greenhouse with LEDs.
 
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