Lumens per square foot?

[Disco94]

Istart of seedling with 4 ft fluros I got at Home Depot for $10 a piece just like the ones you see in cielings but more portable. Bulbs are cheap. Once they get bigger I move the fluros to the sides and put CFLs in over them and then HPS for my last 2 weeks.

 

[StoneyBud]

Istart of seedling with 4 ft fluros I got at Home Depot for $10 a piece just like the ones you see in cielings but more portable. Bulbs are cheap. Once they get bigger I move the fluros to the sides and put CFLs in over them and then HPS for my last 2 weeks.

That really doesn't tell us anything about what lumens per/square foot of plant canopy you're using.

Can you tell us that about each stage of your grow?

 

[Rolling Thunder]

However, if you're looking for healthy, thick stemmed, short node, fast growing, thriving plants, you need to approximate what the Sun does in natural light.

The sun, at high noon on the equator, provides about 10,000 lumens per/square foot of surface.

I totally agree with the above statement; which means 10,000 lumens per sq ft is the natural target range, for growing equatorial sativas (indoors). The further north a plant originates, the less of a difference the extra lumens will make; since we are seeking, after all, to reproduce the plant`s natural habitat indoors.

The 5K lumens is the current cost effective amount. More than that, up to the 10K that you get from natural sunlight, is cost prohibitive.

Dealing with electrical costs, heat build-up, air movement and IR from the lamps make 5000 about as much as anyone would want to put on an inside crop.

It would certainly make it cost prohibitve if there was no difference in the crop yield; or if one was not interested in yielding 1.5 to 2.0 lbs per sq metre. That is the question, essentially: Will a maximum of 5000 lumens per sq ft produce the largest possible indoor yield?

It's the maximum you'd want, not the minimum.

More than that and you start running into lots of other problems.

I`m just curious, but is that what the majority of grow guides say? Are these problems insurmountable? CO2 supplementation is just one method of effectively dealing with heat stress, but it seems to be the last choice for many growers. I don`t know why?

Dealing with all the issues arising from a higher lumens per sq ft ratio takes some work, to be sure, but it can be done, profitably, imo. But then we`re talking about intermediate to advanced growing techniques. - RT

 

[StoneyBud]

I totally agree with the above statement; which means 10,000 lumens per sq ft is the natural target range, for growing equatorial sativas (indoors). The further north a plant originates, the less of a difference the extra lumens will make; since we are seeking, after all, to reproduce the plant`s natural habitat indoors.



It would certainly make it cost prohibitive if there was no difference in the crop yield; or if one was not interested in yielding 1.5 to 2.0 lbs per sq metre. That is the question, essentially: Will a maximum of 5000 lumens per sq ft produce the largest possible indoor yield?




I`m just curious, but is that what the majority of grow guides say? Are these problems insurmountable? CO2 supplementation is just one method of effectively dealing with heat stress, but it seems to be the last choice for many growers. I don`t know why?

Dealing with all the issues arising from a higher lumens per sq ft ratio takes some work, to be sure, but it can be done, profitably, imo. But then we`re talking about intermediate to advanced growing techniques. - RT

If you used 10K lumens, your yield would increase, but not double from what a 5K lumen grow would produce. It's simply not cost effective to use more than 5K lumens per/sq ft.

If you want to squeeze out every single gram you can, and don't care how much it costs you, then sure, set up 10K and use it. You'll have to setup WAY more ventilation. It would probably double your crop costs and give you maybe another two ounces per/pound grown under 5K lumens per/sq ft.

With an indoor grow, reproducing a plants natural habitat isn't what the goal is. Maximizing the plants growth is. Those are not the same thing.

The "extra" lumens given a plant strain that originates far north of the equator will make that plant grow far better than it would in it's natural environment. The natural environment *limits* the plants growth, it doesn't maximize it. By adding more lumens than the plants natural environment, the plant will outgrow what it *would* have done in that natural environment.

The difference between the crop yield when grown in 5K lumens per/sq ft and that of an identical grow in twice the lumens wouldn't be worth the difference in dry weight or potency.

If I grow a second crop of weed at 5K per, I'll end up with WAY more weed than you will if you use 10K per on a single crop, and our costs would be very close to being the same. As an example, I would end up with 40 ounces of weed and you would have 25, maybe.

Why would anyone want to do that?

 

[BBFan]

I'm not sure I agree with the lumens per square foot based canopy measurement Stoney.

Let's suppose I have a plant that is approximately 24" in diameter under a 400 watt hps with a good reflector in a 10 ft x 10 ft room. Am I giving that plant 12,500 lumens (based on an average initial output of 50,000 lumens from a 400 watt hps)? How does disbursement of the light factor in? Isn't that why we use reflective walls in our grow space, to capture some of that otherwise lost light? The spread of the light plays a major role in the efficiency of our space, doesn't it?

When lamp output is rated in lumens, that's at about an inch from the bulb. You get to 12" and you're down to a quarter of those lumens- at 3 feet from the lamp I think it's around 1/9th the lumens. Now if we can measure lux at the canopy, that would probably be a more accurate measurement.

As far as mimicking / improving on the plants native environment, there is simply no way any light is going to give you the penetration of light that the sun gives.

I grow in a 2.5 ft x 4 ft box under 2- 400 watt units. I supplement that with some smaller HID units for side lighting. I started out with 1 - 400 watt unit in that same box, and I can tell you that adding the additional light has more than tripled my yield. Granted, my canopy has increased, but still, that's a marked improvement.

 

[StoneyBud]

When lamp output is rated in lumens, that's at about an inch from the bulb. You get to 12" and you're down to a quarter of those lumens- at 3 feet from the lamp I think it's around 1/9th the lumens. Now if we can measure lux at the canopy, that would probably be a more accurate measurement.

Dude, as I told you in my PM, I've just returned from a party. I'm toast.

However, the first thing we have to fix is what you think are the criteria for measuring lumens is.

It's a measurement of the light that strikes the surface of a globe, from exactly 12 inches. Measured in protons.

Please, reform your question into the limitations of those parameters, and tomorrow, when I haven't as much to drink or smoke, we'll progress from there.

I know that you are coming from a stance of what you consider to be the facts of the problem, but you and I need to discuss the problem in detail before drawing conclusions.

Ok, I'm seriously toasted. I'm hitting the sack.

 

[BBFan]

Hey Stoney- Hope you enjoyed the party!

This is from Wikipedia, and basically sums up my understanding of lumens and the rating of the different lights we use in terms of output:

The lumen (symbol: lm) is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. The lumen is defined in relation to the candela by

1 lm = 1 cd·sr
That is, a light source that uniformly radiates one candela in all directions radiates a total of 4π lumens. If the source were partially covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens. The luminous intensity would still be one candela in those directions that are not obscured.



The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. Mathematically, 1 lx = 1 lm/m2.

A single fluorescent light fixture with an output of 12000 lumens might light a residential kitchen with an illuminance of 500 lux. To light a factory floor with area dozens of times that of the kitchen would require dozens of such fixtures. Lighting a larger area to the same level of lux requires a greater number of lumens.

I understand that to mean when discussing the lumens produced by a particular bulb, we are discussing the output in terms of energy at the source.

I'm no expert Stoney, so I welcome any insight you can offer. Thanks.

 

[StoneyBud]

Hey BBFan, you've shown an example of the dissipation rate of lumens, but not how the industry standard of the measurement of lumens is accomplished.

One lumen is the light of one candle power on each square foot of a surface of a sphere at a radius of one foot from the light source.

This is the standard used by all light manufacturers so that the term retains meaning.

 

[StoneyBud]

BBFan, are you telling me that if you grew one crop in a 24" x 48" area with one 400 watt HPS, and another identical crop in the same size area with two 400 watt HPS, that the addition of the second bulb would triple the cured weight of your crop when compared to the one bulb crop?

This would have to be done from seedling to harvest on both crops.

Have you done this?

 

[BBFan]

Hey Stoney-

I was misinformed on the true definition of lumens, thank you for clearing that up.

So as an aside, would you think that if I am able to keep my plants closer than 12" to the bulb, that I am actually getting more lumens on the canopy? I knew I should have paid more attention in Physics (oh wait I didn't take physics, I didn't even graduate high school ).

But dissipation of lumens is critical to what we do. Under 1 single 400 watt bulb, again using a good reflector, the plant directly under the light at 12" away is receiving significantly more light (presumably the full 50,000 lumens that the bulb is putting out) than a plant to the side, at say 24" from the bulb- at that distance isn't it only 1/4th the amount of lumens? Is that your position?

To answer your second post- Yes, I grew in a 30" x 48" home built box, from seed, 2 separate grows: the first under 1- 400 watt unit, the second under 2- 400 watt units. And on a plant by plant comparison, I yeilded 70% more dried and cured bud on the second harvest than the first. Overall yield was actually 4 times the amount of cured product, but I was able to grow more plants. There were other factors and differences involved here, but the lighting was by far the single greatest differentiating component. I am not stating this as any sort of proof, but rather as anecdotal results.

Thanks again for your comments and I look forward to continuing this discussion.

 

[StoneyBud]

Hey Stoney-

I was misinformed on the true definition of lumens, thank you for clearing that up.

So as an aside, would you think that if I am able to keep my plants closer than 12" to the bulb, that I am actually getting more lumens on the canopy? I knew I should have paid more attention in Physics (oh wait I didn't take physics, I didn't even graduate high school ).

But dissipation of lumens is critical to what we do. Under 1 single 400 watt bulb, again using a good reflector, the plant directly under the light at 12" away is receiving significantly more light (presumably the full 50,000 lumens that the bulb is putting out) than a plant to the side, at say 24" from the bulb- at that distance isn't it only 1/4th the amount of lumens? Is that your position?

To answer your second post- Yes, I grew in a 30" x 48" home built box, from seed, 2 separate grows: the first under 1- 400 watt unit, the second under 2- 400 watt units. And on a plant by plant comparison, I yielded 70% more dried and cured bud on the second harvest than the first. Overall yield was actually 4 times the amount of cured product, but I was able to grow more plants. There were other factors and differences involved here, but the lighting was by far the single greatest differentiating component. I am not stating this as any sort of proof, but rather as anecdotal results.

Thanks again for your comments and I look forward to continuing this discussion.

I think you're digging a little deeper than necessary on the lumen count.

The basic rule of thumb used by most of the experienced growers here is that 5K lumens per/sq ft of plant canopy is the most cost efficient amount of light to use.

I have no idea what the highest amount of light that can be used by MJ is, but I'm sure that if you managed to put that amount of light on your plants without harming them, it would be more cured weight than what 5K lumens per/sq ft produces.

I still say that if you grow one crop under 10K lumens and another under 5K lumens, with an identical set of all other parameters, then the 10K grow would be less than double in cured weight of bud.

Growing more plants in one test than the other isn't a proper test. It has to be the exact same in both grows. What you've said is that by growing more plants, you had more weight....(I should hope so).

Two 5K lumen per/sq ft grows of four plants would out produce the single 10K grow of four plants.

Let me know if you ever try that. Put a watt meter on everything you use to keep that 10K grow going without any heat stress. When you're done, your costs will be much greater than just the difference in light wattage.

We're talking cost effectiveness.

 

[The Effen Gee]

Are lumens per square foot really important during veggin? I understand it is during flowering, but when veggin only to 12 inches do I really need to live by this? What's a cheap but effective light for veggin 10 plants?

Not really but it helps immensely.

I veg under a 600 hps, and would never use anything else.
Flouros just make weak plants and MH seems to be lacking as well.

I can get fully rooted clones in 9 days from cut under a 600. Actually not direclt under, but off to the side.

With proper rotation, I can fully flower 12 plants under 1 600 that is on a 24 hour straight cycle by rotating the plants in and out of light/closet.

I would recommend vegging under a 600 as I have noticed a 400 can cause weak stalks and other problems.

10 plants, depending on the size can be stored under 1 600.

 

[Rolling Thunder]

It's not feasible to use 10K lumens in a grow room, because the costs would be astronomical, so 5,000 lumens per/square foot of PLANT CANOPY is an amount that most experienced growers accept as a standard to provide as good of growth as can be, inside.

I realize you did not say ``all`` experienced growers think that way, which is a good thing, because it shows your willingness to recognize that there are some who disagree with that rule of thumb; but, I`m curious to know what you think of Rosenthal and Soma as growers. Would you regard them as ``experienced`` or maybe even ``advanced`` growers? - RT

 

[StoneyBud]

I realize you did not say ``all`` experienced growers think that way, which is a good thing, because it shows your willingness to recognize that there are some who disagree with that rule of thumb; but, I`m curious to know what you think of Rosenthal and Soma as growers. Would you regard them as ``experienced`` or maybe even ``advanced`` growers? - RT

Why are you asking me of my opinion of Rosenthal and Soma? If they have done something that you wish to make a point of, why not just say it?

Please keep in mind that I've been growing weed since 1949 when Ed Rosenthal was 5 years old.

The 5,000 lumens per/sq ft of plant canopy is something that is used as a benchmark to new growers to let them know what is a good level of light to use, not as an absolute.

 

[ozzydiodude]

Quit lying about your age Stoney we all know you were born in the B.C age And gave JC his first bag

 

[Rolling Thunder]

Please keep in mind that I've been growing weed since 1949 when Ed Rosenthal was 5 years old.

I had no idea about the length of your cultivation practice, but it is a good thing to know, as I can now see that there is deep roots to your knowledge. I meant no disrespect. To the contrary, I take my hat off to you. But anyway, to the point:

Rosenthal has been in the profession for a long time, though clearly not as long as yourself, to be sure. His thick grow guide, co-authored with Mel Frank and published back in the mid-70`s, was my first exposure to serious cultivation practice. I use to make a habit of skipping off classes in high-school just to go and burry my nose in that text. (Not that I recommend that sort of thing today. LOL) My first indoor grow was in 1981, under florescent grow tubes. Pure Columbian sativa.

Rosenthal`s knowledge and skill, like everyone else`s, has been developing over the years. He doesn`t know everything, to be sure, nor does he pretend to; but in a recent publication of his, he states the following:

"To produce good buds that are dense and filled with sparkling resin glands, the garden requires a minimum of 35 watts of electrical light input per square foot. The buds grow denser and more potent when the plants are supplied with an electrical input of about 65 watts/sq. ft. At a higher intensity a 1000 watt lamp lights an area of about 16 square feet. A 4' x 8' table is illuminated using two 1000 watt lamps ... etc." ( Marijuana Success Indoors, 2002 copyright, p. 10)

``The garden requires a minimum of 35 watts,`` he says, ``per square foot:`` 35w x 140 lm/w = 4900 lm/sq ft. Now, Soma agrees with Rosenthal, and states the following in his book: ``I have five, 600 watt grow lights above the beds giving me a total of 3000 watts. That`s about 60 watts per square foot, or just over 600 watts per square metre ... etc.`` (Organic Marijuana Soma Style, p. 29) Another dude by the name of Mel Thomas, author of Cannabis Cultivation: A Complete Grower`s Guide, writes the following: ``Indoor cannabis gardens require 3000 to 9000 lumens per square foot. Successful gardens receive at least 6000 lumens per square foot ... etc.`` (Copyright 2002, p. 14)

For those who are unfamiliar with Thomas, he was a big-time commercial grower based in London, England. The FEDs code-named him `Mr. Big`, and it took four different police forces working together to bring him down. He was busted for $3.5 million of Skunk weed. The trial judge designated him `a horticultural expert involved in a resolute and successful attempt to produce cannabis on a commercial scale.`(Foreword, p. ix)

There is a good sampling of some experienced growers that take a different view of the question. It would be redundant to quote any others, for the point has already been made, that there are a few well-known and very experienced growers who always grow way above the 5000 lm per sq foot benchmark; which in no way detracts one iota from their skill level as growers.

The 5,000 lumens per/sq ft of plant canopy is something that is used as a benchmark to new growers to let them know what is a good level of light to use, not as an absolute.

Well, I can certainly accept that it is a `good` level of light to grow at, especially for a newbie. That is a far cry, though, from saying that one would never, for any reason, want to exceed 5000 lm per sq ft. Respectfully - RT

 

[Rolling Thunder]

For those who are unfamiliar with Thomas, he was a big-time commercial grower based in London, England. The FEDs code-named him `Mr. Big`, and it took four different police forces working together to bring him down. He was busted for $3.5 million of Skunk weed.

Just a note of interest, that was $3.5 million worth in the early 1990`s. He and his partner were sentenced to over 14 years in maximum security lock-up; and they were ordered to pay over $210,000.00 in fines, or serve an additional 3 years each, on top of the 14, without parole.

 

[BBFan]

What you've said is that by growing more plants, you had more weight....(I should hope so).

Actually, what I said was this:

And on a plant by plant comparison, I yeilded 70% more dried and cured bud on the second harvest than the first.

I based it on a plant to plant comparison, not a net weight to net weight comparison. Specifically, my yield was 33 grams per plant at 400 watt relative to 57 grams per plant at 800 watts. And I would venture to say that had I grown the same number of plants, the differences would have been greater due to increased light penetration with fewer plants.

I guess this all started with the lumens per square foot relative to grow space versus canopy. And maybe I'm thinking about it too much. What I am pretty confident about is that 100000 lumens in that space is still not the maximum amount of light I can give them. But I'm working on it.

"To produce good buds that are dense and filled with sparkling resin glands, the garden requires a minimum of 35 watts of electrical light input per square foot. The buds grow denser and more potent when the plants are supplied with an electrical input of about 65 watts/sq. ft.

Don't you think though that this info, even though it's less than 10 years old, is dated, particularly in consideration of LED's?

Forgetting heat issues for a moment, do you think running 400 watts of cfl's in a 10 foot space would be the equivalent of 400 watts of HID? Is there a difference in the quality of light? Or is a watt equal to a watt, regardless of the source?

 

[StoneyBud]

Well, I can certainly accept that it is a `good` level of light to grow at, especially for a newbie. That is a far cry, though, from saying that one would never, for any reason, want to exceed 5000 lm per sq ft. Respectfully - RT

Who said that? I surely never did. I said, many times, that 5000 lumens per/sq ft was the most cost efficient amount, and with your examples, you also said it.

May we quit beating this dead horse?

 

[Rolling Thunder]

Don't you think though that this info, even though it's less than 10 years old, is dated, particularly in consideration of LED's?

Yes, it is very dated! His magazine coloumn(s) will contain his very 'up-to-date' knowledge and practice. I know for a fact Rosenthal is currently working on a test project with an LED company. Just as he was one of the earliest to go totally HPS, and promote solo HPS growing, I suspect he'll become one of the very first 'big' promoters of LED as well. I myself have full intentions of going all LED before long, and then eventually plasma; if I can convince myself that the plasma light source is superior to LED.

Forgetting heat issues for a moment, do you think running 400 watts of cfl's in a 10 foot space would be the equivalent of 400 watts of HID? Is there a difference in the quality of light? Or is a watt equal to a watt, regardless of the source?

To be honest, I have'nt given cfl's much thought. My attention has been more focused on MH and HPS, until recently. Now it is more focused on LED and Plasma lighting, though I still have my doubts about the grow capacity of Plasma lighting. From what I can see, or my limited perspective, the immediate future belongs to LED lighting. If you have money to invest, invest it in some LED light stock(s). Plasma lighting will still take a while to get it together.

Based on the little I know about cfl's, I'd chose 400 watts of HID over 400 watts of cfl, any day of the week; but as I say, I'm not that knowledgable of the state of the art cfl, and its true growing capacity. - RT