Lumens and number of lights

[sharer6969]

For a fairly small grow cab situation (no bigger floor area than 2' x 3', or possibly 2.5' x 2.5'), I was debating which would be the best use of light, considering...

- I don't want a lot of noise
- I want to use as little power as possible
- I have no immediate plans for C02 enrichment.

As such, I'd like the lights to give adequate light per square foot, but not generate unnecessary heat (necessitating further climate control measures, hence more noise and more power consumption.)

I also realize that the further a light is from the plant itself, the less lumens the plant is receiving. If lumens are measured 1' from the light over a 1' square area, then a "larger" single light above the center of the garden is going to give the most light in the center, less so as you go outward. Further, I'm aware that the lumen value listed in the manufacturing details drops after you go 1' away.

Given this, and my desire for a consistent crop (both in terms of quality and height) in a Sea-of-Green cabinet set up, I was thinking - wouldn't I be better served by running several smaller wattage HPS lights, instead of one larger one? The way I'm figuring this, it could very well wind up involving the use of less power per harvest for more actual lighting.

Judging from my energy bills and the 1000kwh price, even the price of bulbs over the crop's lifetime would not put me over (since replacing one say, 400w bulb is cheaper than replacing 6 x 50w bulbs in a 2' x 3' area.) In theory at least, I should also be able to place these bulbs closer to the plants than a single larger light, thus increasing efficiency.

I've read that 2000 lumens per ft/sq. is the absolute least I would want to go with. Some say 2500 is the healthy minimum. However I've also read that over 3000 lumens per square ft. is only good if you have everything else keyed in, including the proper use of C02 enrichment.

So is my thinking correct...would 6 x 50w HPS be better for my situation than a single 400w bulb? It would also seem to ACTUALLY match up to the talk of "50w per square foot" which many grow FAQ's mention (where as it would seem a larger single light solution would not, at least not for outlying plants in the garden.)

On paper this sounds good, based on everything I've read. Am I missing something though? I guess the real clincher is if I can in fact keep a 50w HPS bulb (1900-2200k) 12" away (or just a bit more if need be) from the plant tops? Would that be possible with reasonable ventilation (but nothing too heavy duty), or would that be still likely to burn the plants?

I'm just very skeptical that "a big friggin' light" is always a good thing. I'm just interested in keeping a regular stash on hand, with some to spare (will personally smoke 1/2 oz. a week, tops...I mean, that's if I have a lot of free time on my hands.)

[420Paul]

Some one answer this question, because I have found that 75wt hps, lamps are much cheaper, plus you have no ballast to deal with, cause you can get them internal!

[bejay]

to my knowlege all hps requires a ballast but some of the smaller ones may use a smaller socket.
as per using 6 50's instead of one 400 thats really not a good idea as you would need about 12 50's to come close to equal the lumen output of the 400
so the 400 would be the obvious choice for a 2 by 3 area.
or maybe a 250 for a 2.5 sq area.

[Scarlet Sky]

a 400w would be the cat's ass in that space. as far as co2, yeast and sugar babe ;) works like a charm

[sharer6969]

Thanks for the input so far, gang. :)

Before asking for any more elaboration, I think it'd be a good idea to outline the basics of my plan first, and perhaps most importantly, explain my priorities with this grow.

I'm not looking to get into 'sales' or anything like that. This is for personal consumption. Me and my old lady only smoke 1/2oz. per week, tops (more like 1/4oz. actually.) The wife is a "cheap stone", and I just don't smoke ALOT myself - just a little bit on a fairly regular basis, a little toke instead of a cocktail after work like most regular-light drinkers would have a couple of beers or shots of scotch at the end of the day, and maybe a six pack with the boys on Saturday. I work the night shift, so I'm actually having a puff right now while I talk to you fine folks. ;) (I'm not sure exactly what it is, but it tastes like a soil grown, citrussy herb slanted heavily on the Sativa side of the gene pool...very nice, very cerebral which is generally my favourite "type.") Pot actually saved me from a growing alcohol problem, but that's another topic for another forum. Suffice it to say, I can see why con-artists like D.A.R.E. get so much of their funding from the alcohol industry...

N-E-Ways, those are our needs. If I can also donate a little herb now and then to the local compassion club as well, all the better. I only regret my father wasn't more "open" about cannabis use, as I think his stress and chronic arthritis could be helped a lot by a little toke now and then...but if I can't give it to him, I'll give it to someone else's ailing father.

Now, my idea on how to accomplish this economically and safely is to have a few little grows going on at once, each at different stages of development, with the goal of a ready crop about every 3 weeks. That also gives adequate time for the harvested crop to be manicured and dried in a small space. By the time the next crop is ready to be picked and thrown in the drying box, the previous one will have just been taken out of it and put into a jar for curing.

So I want high quality and sufficient quantity. And very very stealth. And so long as those conditions are fulfilled, as cheap and low maintenance as possible.

The plants themselves will be an indoor variety known for having a very dominant main cola. They will be allowed to veg under an MH light for only a week-or-so after rooting. Also, as they flower, it's likely the lower branches will be clipped so as to further promote dominant top growth. They'll also be really packed in as well - probably at a rate of 3 or so per square foot by the time they're approaching harvest time. I'm hoping they'll be no taller than 20", shorter prefferably. This is intended to be pure Sea-of-Green; a tight canopy of "tops." All clones, all uniform in terms of genetics and growing conditions.

Now, I'm well aware that for sheer lumens, the bigger the wattage, the better. However, this creates a lot of heat; more than the plants care for if they're too close or the ventilation is not strong enough. Further, I'm inclined to believe that there is a point where the use of super high-intensity lighting is only noticably beneficial when all sorts of other strategies have also been implimented (C02 injection being the biggest one, but a super keyed in nutrient regime and hydroponics would be others.)

But more than any of this, I find the physics (as I understand it) involved to be compelling. It's my understanding that "lumens" are measured in a one square foot area exactly one foot away from the light source. The further you move beyond this, the more this amount of light diminishes - and dramatically! At 2' this rating should be cut to a quarter - so that means 40,000 lumens becomes 10,000. And even if your distance is only 18", that still means you may be only getting half of the light's lumen rating on your plants.

So, if a smaller light doesn't radiate as much heat, that means (at the very least) that they can get quite a bit closer to the plants, esp. because it will not be as intense at any one point (the "damage" is spread out very evenly).
And because they are closer, that means the amount of lumens the bulb is rated for (or perhaps even more if you can get closer than 1ft.) will actually get on the plant.

So looked at this way, the ability to keep the lights closer to the plant canopy will offset the lack of sheer individual "bulb power."

Further, I'd even argue that you could get away with a lower total wattage use and get similar/same (or maybe even better) results.

I've read from forums like this that you need at least 2500 lumens per actual square foot to grow good smoke. Well, the 50w HPS's I've seen are listed as 3600 lumens. That means at one foot away from the light over a one foot square area (someone please correct me if I'm misunderstanding this!), the gauges they use measured 3600 lumens.

Well, a 400w HPS I see listed on a lighting website says it's rated at 37,000 lumens. that's obviously a lot more than 3,600! But that's a misleading number if I have to keep the bulb more than a foot away from the plant canopy. Further, that amount of light diminishes the further out and away from "directly under the light" one goees. And that's something I'm inclined to think may get worse with time, not better, as the plant directly under the light will grow faster than the others, thus requiring the light to be raised even more up and away from those shorter plants. Further, more light doesn't just mean more yield, it means stronger dope. So keeping those tops uniformily well lit is important, even just to keep the end product consistent.

So is all of this blabbering really misguided, especially considering my objectives? Or even if it will fulfill my objectives, is it still less efficient and/or cost effective than simply going with one big light? Am I highly over-estimating the heat issues that would be created by a 400w bulb, so my stressin' over keeping it too close to the plants in such a small space is really a lot of worry over nothing? Because if I can safely and economically keep that 400 watter 1' or less from most of the plant tops (it's a pretty small space after all), then I guess that would be the way to go.

So I'm lookin' to be convinced folks! I want to not go into this half-assed and without having a plan together. Economical, simple, but not half-assed.

[sharer6969]

a 400w would be the cat's ass in that space. as far as co2, yeast and sugar babe ;) works like a charm

Hi(gh?)!

Yeah, I've considered something like that. However, I have heard very mixed things about such homemade solutions. While I don't have any doubt that they're not effective for large growing areas, I'm still undecided about their use in small areas.

So you say this works well for you? I guess my only question would be if you have experience under similar (or the same) growing conditions, but without the home-brewed C02? I ask, because what the "con" side generally says, is that people end up crediting their home-brew C02 systems (which they say don't really produce much C02 at all) for something it didn't really do. Something to compare it to would either support or challenge that assertion.

If it does work, however, I would definately take advantage of it, if playing with the venting would not involve too big (or elaborate) a set-up. Obviously if using C02 would get me more bud in the same space, I'd be interested - since it would mean I could just use less space (since I'm really only growing for myself and "the missuss", and the odd "session" I host.)

[bejay]

most 400 watt lights put out about 50000 initial lumens there is some grow bulbs that put out a little more than that. and it would be easier to cool one bulb in one air cooled reflector than all those small bulbs put together.
the small hps are not used much because they do not put out very many lumens you can buy a cfl with about equal lumen output as a 50 watt hps,
you shouldnt have much problem with a 400 in a cool tube or other air cooled reflector, you should be able to get the light about 6 inches from the tops of the plants the 12 " and even further distances say for even larger lights is more or less a guideline for open reflectors that are not being cooled.
you should put up mylar or something comparable on the walls to reflect the light back to the plants and prevent wasting any light.

[420Paul]

to my knowlege all hps requires a ballast but some of the smaller ones may use a smaller socket.
as per using 6 50's instead of one 400 thats really not a good idea as you would need about 12 50's to come close to equal the lumen output of the 400
so the 400 would be the obvious choice for a 2 by 3 area.
or maybe a 250 for a 2.5 sq area.

Some of the smaller 75wt hps lights ie, they used to use HPS for security lights, but people prefer mh because of the blue color instead of the yellow, but you can find small enough hps lights, with bulit in ballasts.

[bejay]

yes you can get the small security lights with a built in ballast but really they are not that great of a deal in my opinion you could get a better light with a remote ballast the ballast itself can put off quite abit of heat wich is why its better to have a remote ballast to remove the heat from the grow space so you only have to deal with the heat from the bulb have seen the small security lights turned into a remote ballast by taking them apart, but whatever light you decide to use, you should use your sq ft of grow area for determining light size and get atleast 50 watts per sq ft.

[kindprincess]

Hi(gh?)!

Yeah, I've considered something like that. However, I have heard very mixed things about such homemade solutions. While I don't have any doubt that they're not effective for large growing areas, I'm still undecided about their use in small areas.

So you say this works well for you? I guess my only question would be if you have experience under similar (or the same) growing conditions, but without the home-brewed C02? I ask, because what the "con" side generally says, is that people end up crediting their home-brew C02 systems (which they say don't really produce much C02 at all) for something it didn't really do. Something to compare it to would either support or challenge that assertion.

If it does work, however, I would definately take advantage of it, if playing with the venting would not involve too big (or elaborate) a set-up. Obviously if using C02 would get me more bud in the same space, I'd be interested - since it would mean I could just use less space (since I'm really only growing for myself and "the missuss", and the odd "session" I host.)

hey babe, i'm using co2 on this run, first time. i've always gone with a fresh air intake, but this time i'm trying the other way (because my fan is WAY TOO LOUD!) i have MAJOR differences in bud density and quantity. plants are growing like they are in the tropics. i don't have any pix to compare as of now, but can probably manage to get a comparison tonite. it won't add a lb, i'm sure, but i got two to four ounces a plant before, i harvest at the end of march.

as far as a big space, my flower room is 12x16. i'm using two 5g jugs and two one gallon jugs. recipe is :

5cups water
2cups sugar
one pack yeast (highly active)

that's for a one gallon. for a larger jug, just multiply amounts by the # of gallons.... shake twice daily. in two weeks, ad one cup of sugar per gallon to each jug. these can last as long as 6 weeks (so i've been told)

my jugs fill the whole room with co2 (know how you can taste the co2 in the first sip of a coke or pepsi?) if you stay in there for a while, you'll get light headed :) i have NO idea what the ppm is, i just go by the "taste"

hope that helps.

also, you are MUCH better off with a 400w than with several smaller ones. trust me, a 400w is PERFECT for your space; it will light every square inch.

[Shovelhandle]

(I posted this somewhere else on this board)


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Shov