Lumens per square foot?

[Rolling Thunder]

May we quit beating this dead horse?

Most certainly. As I said, no disrespect was intended. :48:

 

[stonedrone]

I'm going to go ahead and jump in here.

I have seen several very successful grows on this site using well below 5k lumens per sq. ft. Many of the grows that I have witnessed just shot for over 3k psf. That square footage was based on the size of the grow room in each of these grows.

Stoney this is the first time I have seen somebody say that the room size is not what is important but rather the size of the canopy. While that does make some sense to me as you need sufficient lumens to penetrate said canopy, you will actually increase the amount of lumens that hit the plant with a good reflective surface close to that plant. There is such a thing as lumens dissapation that is why all manufacturers test under the same circumstances. I do agree however that you can have a successful grow with one 400w light over the top of 2 to 4 plants in any sized room however you will increase the amount of lumens that hit said plants in a smaller room with reflective walls, hence increasing growth rate and overall yield.

One more thing that I am sure of is that every time you double the distance from a light source you decrease the amount of light hitting a certain point by 75%. For example if you have 50k lumens at 1 ft you have 12.5k lumens at 2 feet.

 

[StoneyBud]

Stoney this is the first time I have seen somebody say that the room size is not what is important but rather the size of the canopy. While that does make some sense to me as you need sufficient lumens to penetrate said canopy, you will actually increase the amount of lumens that hit the plant with a good reflective surface close to that plant.

The reason I said that is for this example:

Mr. Smith has 4 seedlings that are each 2 inches tall. He places the seedlings in his grow room which is 12 feet by 12 feet in area.

His seedlings are in the center of the room.

Now:

1. If room size were the way to determine your light amount, then Mr. Smith would need lights creating 720 thousand lumens to cover his entire 12 foot by 12 foot room at 5,000 lumens per/sq ft.

2. If plant canopy is used to determine how much light is used, then Mr. Smith would find he needs 5,000 lumens over his seedlings.

Please, the 5 thousand lumens is just an example. Don't freak out on me about the 5 thousand lumens per/sq ft.

My question is this; Why would Mr. Smith use his room size as the determining factor for his lights on the 1 square foot of plants in the middle of his room? What if his room was 200 feet by 200 feet and he only used the center 1 square foot of area?

So, with that in mind, THAT is why I said to use the plant canopy size to determine the number of lumens needed. The plants are what is being lighted, not the entire room.

NOW PLEASE FINISH READING THIS:

Later, when Mr. Smith uses topping and LST to FILL the entire 12 foot by 12 foot room, his canopy would then BE THE ROOM SIZE and he would use the room size as his determining factor for light needed.

Do you understand what I'm getting at here?

 

[stonedrone]

I'm not trying to disagree with you Stoney, on the contrary as a matter of fact. I am sure to read every single post of yours that I see on this site. I just feel that it is more beneficial for Mr. Smith to put those 4 seedlings into a smaller area as the light that would normally escape would be reflected back onto the plants. My statement about the 5k lumens was not directed towards you, I was just pointing out that 5k is plenty for a good grow. Most of the experienced growers on this site say 3k is what we need and 5k is what we should be trying for.

Although I may ne be all that eleoquent in my statements I am not trying to say that any one person is wrong. I like to take part in these debates because I tend to retain more information this way. It seems to me that an edjucated debate is more likely to produce facts and proof than just a collection of statements which are usually based in opinion.

 

[StoneyBud]

I'm not trying to disagree with you Stoney, on the contrary as a matter of fact. I am sure to read every single post of yours that I see on this site. I just feel that it is more beneficial for Mr. Smith to put those 4 seedlings into a smaller area as the light that would normally escape would be reflected back onto the plants...

I agree also. Lots of people here start their grows with huge lights over tiny seedlings. I was attempting to show that if someone had a smaller light to start off with, they could save some money AND have great results by lighting only the plant canopy initially. That would take much less light.

Some growers also have very limited funds and use only small CFL's to light their grows. By lighting only the canopy, they can also save money by using only the amount of lights needed at each stage of the grow.

 

[stonedrone]

I like the way you explain things Stoney. Thanks.
:48:

 

[Rolling Thunder]

It seems to me that an edjucated debate is more likely to produce facts and proof than just a collection of statements which are usually based in opinion.

Hey there stoned,

How's it goin' dude? You would'nt be implying anything, would you? Let the record note that educated people read and take into consideration the opinions of others better educated and trained than themselves. I deferred to Rosenthal, Soma, and Thomas because I regard them as superior growers, to myself. Try and get through College or University without ever "quoting" other sources of information. The quotes I posted are firmly grounded on years of empirical observation and first hand knowledge of the subject at hand. Peace bro'! - RT

 

[stonedrone]

That's exactly what I'm talking about Rolling Thunder. Although not in the context you seem to have taken it. What I mean is that when you are debating with somebody you are almost required to show some sort of proof or a quote from a professional rather than just answering a question with your thoughts. I'm a straight forward person and I don't tend to imply anything I may disagree with.

You quoting Rosenthal, Soma, and Thomas is part of what makes this an edjucated debate rather than just a collection of opinions. Cheers.

 

[Rolling Thunder]

You quoting Rosenthal, Soma, and Thomas is part of what makes this an edjucated debate rather than just a collection of opinions. Cheers.

Well, just leave it to me to get my wires crossed again. Thanks for clearing things up for this stoned homer. Btw, great signature you got there. I just noticed it! Socrates was the man, indeed! :48:

 

[stonedrone]

:bong: :48: :argue: :bong: :48:

 

[Pepper]

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?

To answer your question in a very simple way

The very simple answer to your question is YES the more light the better, and if someone tells you otherwise they are full of it, plain and simple, and if you are looking for yield leave the word cheap at home because it does not belong in the garden A plant 12" tall tells me nothing. How wide is the plant? You can have a plant 12" tall that is 8" wide and you can have a plant that is 12" tall that is 20" wide so has you can see that makes a HUGE difference in the amount of light you will need. If I were you I would use a minimum of a 400w hps for vegge 600w hps would be even better, and a 1000w hps even better in my experiance hps works much better for vegge than MH that is why I do not vegge with MH bulbs.

Many growers make the mistake of "ignoring" the vegge period but little do they know the vegge period is THE most important phase of a plants life IT will make or break your final yield.

First question you need to ask YOURSELF is. What is the main reason I have a garden, and how much yield do I want? THE answer to that question will dictate how much light you will be using in your garden plain and simple.

Always mesure light usage by plant canopy, and not by the size of the floor space, also VERY important idially the plant canopy should be no more than 1' away from the walls of your room, the reason for that is better light penetration throu the plant canopy.

 

[uptosumpn]

Ok, so I think I got it......If using a 400HPS, (limited funds right now) which produces around 55,000 lumens, I can get the "benchmark maximum" of 5000 or more amount of lumens per SF "plant canopy" If I put 12 plants in 7" wide 3gal bags with 3" spacing between them in a 3.5'w x 3.5'd "plant canopy area??

 

[BBFan]

Ok, so I think I got it......If using a 400HPS, (limited funds right now) which produces around 55,000 lumens, I can get the "benchmark maximum" of 5000 or more amount of lumens per SF "plant canopy" If I put 12 plants in 7" wide 3gal bags with 3" spacing between them in a 3.5'w x 3.5'd "plant canopy area??

If you're planning on growing in a 3.5' x 3.5' under 400 watts, you'd be better off only doing 4 plants in 5 gal pots. My space is very similar to that (2.5' x 4') and I use 2- 400 watters. The most I fit under there is 8 plants, and I didn't maximize yield. I'm trying the less is more approach.

Good luck to you!

 

[uptosumpn]

Ok, I just realized I had the plant count wrong...after talking with a friend who used 3 400watt hps, (130,000 lumens) in a 24sf area.(3'd x 8'w) He put 8 plants in 2gal bags under each light and got an average of 2oz dry per plant ...(autos) which is what i'll be growing:hubba: So yes, less is more, but not 4?! BTW, I already have 3gal bags..so gotta use what i have. Thanks

If you're planning on growing in a 3.5' x 3.5' under 400 watts, you'd be better off only doing 4 plants in 5 gal pots. My space is very similar to that (2.5' x 4') and I use 2- 400 watters. The most I fit under there is 8 plants, and I didn't maximize yield. I'm trying the less is more approach.

Good luck to you!

 

[The Hemp Goddess]

Ok, I just realized I had the plant count wrong...after talking with a friend who used 3 400watt hps, (130,000 lumens) in a 24sf area.(3'd x 8'w) He put 8 plants in 2gal bags under each light and got an average of 2oz dry per plant ...(autos) which is what i'll be growing:hubba: So yes, less is more, but not 4?! BTW, I already have 3gal bags..so gotta use what i have. Thanks

I'm sorry, but I have a very (very, very, very, very...) hard time believing that your buddy was getting this kind of dry yield--over 1 gram per watt with autos in 2 gal bags that were only given 1 sq ft each????????

Do not expect anything close to this, especially when you are starting out. If you get 1/4 oz per watt with autos when starting out, this is good.

 

[uptosumpn]

My mistake! Hemp Goddess, I was quoting his yeild amount from his other grow using 2 x 1000hps in a 25sf area...! with 23plants @ 2+ oz each....

But, with the 3 x 400hps he got 1oz dry per plant! with 7 plants underneaath each 400hps...I was high.. {1oz per. is the amount i'm going for:hubba: }

I'm sorry, but I have a very (very, very, very, very...) hard time believing that your buddy was getting this kind of dry yield--over 1 gram per watt with autos in 2 gal bags that were only given 1 sq ft each????????

Do not expect anything close to this, especially when you are starting out. If you get 1/4 oz per watt with autos when starting out, this is good.

 

[BBFan]

My mistake! Hemp Goddess, I was quoting his yeild amount from his other grow using 2 x 1000hps in a 25sf area...! with 23plants @ 2+ oz each....

But, with the 3 x 400hps he got 1oz dry per plant! with 7 plants underneaath each 400hps...I was high.. {1oz per. is the amount i'm going for:hubba: }

He must be an amazing grower. You should listen to everything he tells you and not bother with the people here. That's still over 2 grams per watt - tell him to sign up here- I could use some advice from him!

 

[MrNorCal]

He must be an amazing grower. You should listen to everything he tells you and not bother with the people here. That's still over 2 grams per watt - tell him to sign up here- I could use some advice from him!

Hey BBFan I think your math is a little off. Either that or mine is(which is entirely possible) But when I plug in the number I am getting 0.644 grams per watt with the 1000's and 0.49 grams per watt with the 400's for this guy's grow.

 

[BBFan]

Hey BBFan I think your math is a little off. Either that or mine is(which is entirely possible) But when I plug in the number I am getting 0.644 grams per watt with the 1000's and 0.49 grams per watt with the 400's for this guy's grow.

Hi MrNorCal- How's the grow room going?

You're absolutely right! It's my math that was off!

Please accept my apologies uptosumpn.

 

[uptosumpn]

No problem man...that's what this site is for right? to have constuctive criticism.....

anyway, he is a member here...and here is his journal from start to finish.....! big room sf with small plant canopy sf...just like what Stony Bud has been saying.....
http://www.marijuanapassion.com/forum/showthread.php?t=20531