Lumens...and How much your Grow Room needs!!

Cannifornia

Member
so i hear that veg stage needs roughly 2,5k to 3k per sq ft.

then I heard flowering stage they need 10k per square foot...

doesnt the sun give out like 8k per sq at max?

and cant the plant only absorb 7.5k per sq foot?

MY QUESTION IS..

my setup is 4x5 putting it at 20 sq ft.

I plan on using yieldmaster [SunSystem] 600w Hortilux at about 95k lumens.

will i have any problems in flowering stage?

some skeptics have made me skeptical...:shock:

any friendly experts out there?
:weed:

thanks in advance,
Cannifornia
 

darkdestruction420

Well-Known Member
Those are rough guides for good growth and such, sure you could use less or more than that, but it will effect your yield. the sun puts out like 100,000+ a square foot on a sunny day in direct lighting. the plant can for sure use more that just 7.5 thousand per square foot easily.
 

legallyflying

Well-Known Member
Those are rough guides for good growth and such, sure you could use less or more than that, but it will effect your yield. the sun puts out like 100,000+ a square foot on a sunny day in direct lighting. the plant can for sure use more that just 7.5 thousand per square foot easily.
That is not what books on the subject say. They list 7.5 as the upper limit of plant utilization (marijuana growers bible).


Its easier to deal with watts/foot or some other measure as there allot of factors that go into the footprint of your bulb. Chiefly, your hood design. All hood are not created equal. Therefore, people often state a size of a grow area instead of lumens. I wish people would stop talking in lumens and just talk lux because lux is the only thing you can measure, and when you get down to it,is the more important of the two. Your 9.5k bulb will fade to about 7.5k in about 6-8 inches.

Yeah, your bulb gives off X amount of lumens.. how many of those lumens are actually reaching your plant though? That's the really important part. Lux is the common measure of light intensity that you can actually measure. 1k lux equals ROUGHLY 10k lumen. I probably spent 3 hours with my lux meter and a grid finding the best height for my hoods and the size of my SCROG net.

When dealing with these issues it is best to consult the published books on marijuana cultivation and setting up grow rooms. If you pick through forum responses you will inevitably find a piece of information that is not really correct, or partially correct..thus making your decision making process more difficult.

Based on my literature review..

Optimum grow space per bulb
400 watt system 3x3
600 watt 3.5 x 3.5
1000 watt 4 x 4

Most efficient duration for veg growth = 18 hours a day. After this point, the ability of the plant to process light and produce sugars fades rapidly. 18 hours is the point of diminishing returns. You can piss away your money on electricity but those extra 6 hours are getting you less and less return as you go past 18.

Most efficient Co2 = 1300 PPM. The rate of photosynthetic rate increase with increased co2 saturation is not linear. It increases rapidly at first, levels off, then increases again with temperature. The rate of increase pretty much flat lines at 1300. From 1300 to 1500 there is a TINY increase but to me (because I have an advanced ppm controller) that extra 200 is kind of wasted.

just my 2 cents. Some people want to provide the ultimate growing environment and some people are growing plants in a computer case with a single CFL bulb. It's all good in my book.
 

Cannifornia

Member
thanks for response. pretty helpful.

my room is 6.5ft by 3 ft.

im ordering the 600w HPS Hortilux bulb with yield master reflector with mylar on the walls.

(6) 3 gallon pots. 2 rows of 3.

giving each plant about 22"x18" to grow.

it wouldnt hurt getting a 1000w bulb but 600w would work just fine im sure.

3 gallon pots of indica can achieve like..3-3 1/2, 4 ft if im lucky?

im fine with that. my room is 7 feet tall so with the reflector, and pots, and distance from light i could grow about 50" max
 

legallyflying

Well-Known Member
you should really look at the supersun 6 hood.. Scored much better in terms of overall light intensity and eveness among 6-7 hoods that were tested.

a 600 watter is not going to effectively penetrate more than 3 or so feet anyways so you are good. I would probably increase planter size, stagger them in rows, and SCROG for the highest yield.

check out the SCROG screen in my grow journal.

cheers,
LF
 

Cannifornia

Member
ya ive heard many good things of scrog even like 3/4 pd a plant easily.

i was thinking of doing it but this being my first indoor grow i wanna do all natural to really learn the basic steps to indoor growing.

maybe ill top and lst?

or is SCROGing really an easy way to do it?
 

darkdestruction420

Well-Known Member
either the bible your looking at is wrong or you are misunderstanding what you read, it makes absolutely no sense at all, start a thread on here asking for others advice if you want and youll see. lux is how much luminous flux your lights put out, which is based on lumens themselves. I should of said no they dont have a max luminous flux that they stop using after a point. You should re-read that bible of yours and make sure you understand what your talking about fully. Not trying to be rude or anything of course.
 

legallyflying

Well-Known Member
either the bible your looking at is wrong or you are misunderstanding what you read, it makes absolutely no sense at all, start a thread on here asking for others advice if you want and youll see. lux is how much luminous flux your lights put out, which is based on lumens themselves. I should of said no they dont have a max luminous flux that they stop using after a point. You should re-read that bible of yours and make sure you understand what your talking about fully. Not trying to be rude or anything of course.
Unlike some on the forum, I generally don't post about things that I am not knowledgeable about. Despite the fact that you have 8,700 posts, it seems that you are actually the one that is a little confused on lighting terminology and plant physiology. Your original post (100,000 lumens put out by the sun) is incorrect as is the post that I quoted above. I have seen this number thrown out before by other high posting members but that doesn't mean its correct. The book I referenced is correct as I have seen those numbers stated other places as well (including this forum). The thread starter post is actually consistent with a number of different discussions that I have read on the subject.

Lux IS directly related to lumens but unfortunately, lumens do not deal with area (which is why its not the best way of figuring out lighting in MJ cultivation). Lux is a measure of luminous flux, but more importantly, lux deals with coverage. 1 LUX is equal to 1 one lumen PER SQUARE METER. That is, how much light energy is actually received by a pre-defined area. How much light is given off really doesn't matter. If you had a 1,000watt MH bulb (80,000 lumens) 15 feet above your plants...its not going to be enough to support optimal growth.

The sun actually puts out 3.75×10^28 lumens. (that's 28 zeros after 3.75). Sunlight on the surface of the earth however is around 10k lumens. If the sunlight we see was 100,000 lumens you wouldn't be able to open your eyes lest you go blind. Don't believe me, stare into a 1,000 MH bulb and report back.
If you want to get really technical, comparing HID lumens and sunlight lumens in terms of plant utilization is actually flawed as the light sources are very different. The scientific literature says that a plants ability in natural conditions to utilize sunlight peaks at around 5k. For HID lights, it peaks around 7.5k. For HID utilization of this rate you need proper CO2, humidity and temperature conditions. The ability to use more sunlight is really limited by the physical and biochemical processes related to photosynthesis (concentration gradients, evaporation rates, cellular process).

I'm not going to start a thread to ask advice as the topic has been covered quite a bit. like here......

https://www.rollitup.org/grow-room-design-setup/101350-max-lumens-before-growth-rate.html

https://www.rollitup.org/newbie-central/13968-how-many-lumens-does-sun-2.html

https://www.rollitup.org/newbie-central/13968-how-many-lumens-does-sun-2.html

Not trying to be a dick about it either, just trying to ensure that the correct information is presented. If you have information that demonstrates that plants can utilize "way more than 7.k lumens" I would love to see it.
 

Serapis

Well-Known Member

1971

Member
http://en.wikipedia.org/wiki/Lux I have a lux meter and measured directly under the bulb 9" and the lux reading was mid 70k. Unfortunately the farther you get away from it the less lux you get. That is why I always thought it silly that people would just divide the square foot of their grow room by the lumens of their light or the wattage and think they were providing adequate coverage. If you want good light coverage, use more lower wattage lights. Of course this is more expensive.
 
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