Lighting: How much is too much?

I've done a lot of reading, but still not certain on the correct answer. I have a ten x ten room, painted flat white. Will have a 4x4 tray right in the middle. Have two air cooled hoods. It will be a scrog grow, sativa dominant (green crack). I'm shooting for as high a yield as possible.

Considering the size of the room vs. growing space, for flowering, should I run
a. 2 1000w hps,
b. 2 600w, or
c. one 1000w.

Some say "you can never have too much light." But, I'm pretty sure there is some law of diminishing returns related to the amount of light a plant can utilize, yes?

Others say 50w/sq ft. Still others talk about lumens/sq ft.

I'm leaning toward one 1000w hps. Again, thinking yield, will that suffice?

PS. But its threads like this one that throw me off, ha: https://www.rollitup.org/t/1800w-hps-grow-in-2x2x2m-tent.825258/

thanks!

phil

Hey dude I've seen some amazing results with a 1/200w gravita something or other. The power output could be changed on a dial from 600w to something like 1200w. 30+oz in that space you've got, can't argue with that.

a ten by ten will benefit from two lamps better than one, you'll get better light distribution, in my opinion.
If electricity isn't an issue. Go with 2 1000w or at least 2 600s. I actually use three 600w lamps personally, and my room is similar in size as yours. I've done two 1000s and I seem to get better results with a 3 600w setup, with two 600hps, and one 600 mh. BUT I live in a redwood forest that never gets much hotter than 85 degrees. The 1000s make a little denser nugs, but the light distribution from the three 600 lamps gets me more yields at a better quality, especially when used in conjuncture with the MH. Besides dense nugs are not always good....
I'm a FIRM believer in the added MH spectrums. Makes a better smoke. NO doubt.
I've found a happy goal is around 30-35 watts per sq foot, more than that and you have issue with standard 15amp circuits, and have to go 220v, not to mention that's an ass-ton of heat being put out.

Born Again Vegan said:

Hey dude I've seen some amazing results with a 1/200w gravita something or other. The power output could be changed on a dial from 600w to something like 1200w. 30+oz in that space you've got, can't argue with that.

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Yeah, BAV, some swear by Gavita, others say it's way too hot, but I haven't looked too deep into it because of the other major concern voiced: it's pricey.

greasemonkeymann said:

a ten by ten will benefit from two lamps better than one, you'll get better light distribution, in my opinion.
If electricity isn't an issue. Go with 2 1000w or at least 2 600s. I actually use three 600w lamps personally, and my room is similar in size as yours. I've done two 1000s and I seem to get better results with a 3 600w setup, with two 600hps, and one 600 mh. BUT I live in a redwood forest that never gets much hotter than 85 degrees. The 1000s make a little denser nugs, but the light distribution from the three 600 lamps gets me more yields at a better quality, especially when used in conjuncture with the MH. Besides dense nugs are not always good....
I'm a FIRM believer in the added MH spectrums. Makes a better smoke. NO doubt.
I've found a happy goal is around 30-35 watts per sq foot, more than that and you have issue with standard 15amp circuits, and have to go 220v, not to mention that's an ass-ton of heat being put out.

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thanks, grease. The room itself is ten by ten, but the grow space is actually 4x6 ( 2 trays: a 4x4 and a 2x4, don't think I should try to squeeze all 18 into one 4x4 ). I make the distinction because some believe that you lose light in a bigger room. For instance, I've heard arguments that 2000w / 100 sq ft = 20w/sq ft. Someone can school me, but it seems that most of the light is basically directed downward. I can't imagine that the amount of light lost in a room larger than the grow area would be very significant.

That said, a 4x6 area and (2) 1000w lights = 83w/sq ft. That's a lot more than what many believe to be the "sweet" spot of 50w/sq ft. But, I'm not sure there really is a sweet spot and if there is, what makes it sweet : ).

Of course, as you illustrated, there is the two 600w route, which hits that sweet number for the size of my grow area.

Yup, seen lots of mentions of mixing some MH with HPS and it seems logical, will look into that a bit more, but right now I'm limited to 2 hoods. I have 220v and guess I'll be doing the whole fans/air-cooled hoods thang - hate using that much power, but...

Y'all are the bomb, thnx for the inputs

They're still vegging, below:

there's no such thing as too much light. use as much as you can handle heat-wize. that'll be the problem, heat not light...

even with one of the full hoods you will still lose light in the 8-20 inch gap to the sides. When running a single HID 600 or 1000w this could add up to a lot of light because you would be losing light on 4 sides. roughly 5% of the total light per unreflective side would be my guess.. So about 20% total lost light in a room where the light has no walls to reflect.

20% efficiency is no big deal right? Wrong.

Reflecting also helps hit the plant from more angles which will encourage new growths.

If you want a full spectrum run Ceramic Metal Hallide on a magnetic ballast. Otherwise MH for veg and HPS for bloom. Or even HPS for full cycle (worked great for me).

Silky Shagsalot said:

there's no such thing as too much light. use as much as you can handle heat-wize. that'll be the problem, heat not light...

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Heat will be manageable, prepared for that.

BeastGrow said:

even with one of the full hoods you will still lose light in the 8-20 inch gap to the sides. When running a single HID 600 or 1000w this could add up to a lot of light because you would be losing light on 4 sides. roughly 5% of the total light per unreflective side would be my guess.. So about 20% total lost light in a room where the light has no walls to reflect.

20% efficiency is no big deal right? Wrong.

Reflecting also helps hit the plant from more angles which will encourage new growths.

If you want a full spectrum run Ceramic Metal Hallide on a magnetic ballast. Otherwise MH for veg and HPS for bloom. Or even HPS for full cycle (worked great for me).

Click to expand...

Thanks, BG, will keep that in mind, will try to come up with an idea to mitigate light loss. But, will have to work with what was dealt (some stuff was gifted), the 10x10 room, the odd number of plants, the 4x4 and 2x4 tables, 2 air-cooled hoods, etc.

Thanks!

Silky Shagsalot said:

there's no such thing as too much light. use as much as you can handle heat-wize. that'll be the problem, heat not light...

Click to expand...

True enough. Even with LED panels, when I was running a small cabinet for flowering (2x4x5.5') I tried adding a small panel for side-lighting but the reds generate the heat and had to turn it off, brought my temps over the top...

How many gavita lights would u put in a 1.5x1.5m tent. I currently run 2 600w hps. Should I put 2 600w gavitas or a 1000w gavita.

Since your scrogging it, i would go with 2x600W, its more efficient in terms of LUMENS/WATT of energy. You wont need to penetrate 3 or 4 feet of veg doing a Scrog, so 2x1000w is not needed. 2x600w should be sufficient.
That being said, IF cost is not a major factor, obviously go with the 2x1000W, more light+space=BIG BUDZ.
Oh, and this is just my opinion, however its backed up by 7 grows now, and I find my plants veg WAY slower and stay squat and bushy under MH light, when i just use MH@600w,
I found, for me, the fastest veg i get is under the HPS, with some 6500K CFL or t-5/8 added in, say run the HPS@400w, (adjust respectively to fit your wattage and area) and 250W of T-5. Saves me AT LEAST a week of veg time.