400w vs. 600w for 4x4 tent?

K

kamut

Active Member
I want to veg out some plants under MH in a tent for up to 8 weeks at a time. Do I need 400w or 600w? In the Cervantes book, he is saying that 400 will cover a 4x4 area well, but I am concerned that the plants might be kinda tall, not overly tall. Wondering if I need 600 to penetrate downward.


Thanks!:leaf:
 
bostoner

bostoner

Active Member
A higher watt doesn't get you more penetration, A 600 w would need to be placed further from the canopy at about 16-18 inches for a bare bulb, a 400 would be placed about 10-12 inches, so the light intensity at the top of the canopy should be the same on both about the same as the sun. The only difference is the amount of area covered. Though the sun doesn't have a light falloff measurable in inches. The falloff curve is the same for all same hid bulbs at different watts so say a foot below the canopy they are receiving the same amount of light. So the fact the 400 can cover 4x4 is as good as it gets. A 400 could cover up to 5x5 IMO.
 
Seedling

Seedling

Well-Known Member
bostoner said:
A higher watt doesn't get you more penetration, A 600 w would need to be placed further from the canopy at about 16-18 inches for a bare bulb, a 400 would be placed about 10-12 inches, so the light intensity at the top of the canopy should be the same on both about the same as the sun. The only difference is the amount of area covered. Though the sun doesn't have a light falloff measurable in inches. The falloff curve is the same for all same hid bulbs at different watts so say a foot below the canopy they are receiving the same amount of light. So the fact the 400 can cover 4x4 is as good as it gets. A 400 could cover up to 5x5 IMO.
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Excuse me? Care to elaborate on your statement a little more?

cwdiflamps.jpg
 
hotrodharley

hotrodharley

Well-Known Member
mr2shim said:
600w all day long in a 4x4. I run a 400w in a 20"x36"
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I'm with you. My credo: Go big to grow big.

I know - a 400 will do it and it will.

Jack Connor (long dead) advocated hunting and killing one of everything with a .270 caliber Winchester rifle and he did it too. Including an elephant. I hunt deer with a .30-'06 and carry a .338 Winchester Magnum on hunts here in AK. I want to make sure it dies and quick and with one fast shot.

Hit those plants with that 600 Magnum and make them jump.
 
Seedling

Seedling

Well-Known Member
I have a light meter, and with my 400 and a Hortilux HPS bulb, 8" from the glass of my reflector (Super Sun 2) is 10,000 footcandles, and 18" is 5,000 footcandles. So 8"-18" is the effective range of my 400. A 600 will have a greater range, and of course a 1,000 will have an even greater range.

He seems to think that if a 1,000 watt is 6 feet above the floor, and a 400 is 4 feet above the floor, and they have the same footcandles at 3 feet above the floor (3' below 1,000 and 1' below 400), that they will also have the same foot candles AT the floor. Preposterous I say. :)
 
bostoner

bostoner

Active Member
Seedling said:
Excuse me? Care to elaborate on your statement a little more?

View attachment 2295810
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Well if your talking about PAR and not foot candles its different. Par Photo active radiation, you know the stuff that makes plants grow. When your talking about the human eye you can use lumens or footcandles which convert nicely. 1 FC = 10.76 lux/lumens. When your talking about par its a different story. The par falloff rates of all Mh and hps are the same respectively. So any amount away from the top of the canopy without bleaching your tops from too much par not foot candles is the same par because the falloff rate is basically identical. The person who made your diagram just used footcandles or lumens to come to his findings from the box as if he was lighting a warehouse with it. Same thing will happen with a light meter because its used for visible light not stuff that actually grows plants. If you look around for sites there's converters for par and actually the par from a fluoro is better per watt than a hps just the falloff is so bad that it really isn't an accurate comparison. A MH still beats both in par per watt though. There.
 
mr2shim

mr2shim

Well-Known Member
bostoner said:
Well if your talking about PAR and not foot candles its different. Par Photo active radiation, you know the stuff that makes plants grow. When your talking about the human eye you can use lumens or footcandles which convert nicely. 1 FC = 10.76 lux/lumens. When your talking about par its a different story. The par falloff rates of all Mh and hps are the same respectively. So any amount away from the top of the canopy without bleaching your tops from too much par not foot candles is the same par because the falloff rate is basically identical. The person who made your diagram just used footcandles or lumens to come to his findings from the box as if he was lighting a warehouse with it. Same thing will happen with a light meter because its used for visible light not stuff that actually grows plants. If you look around for sites there's converters for par and actually the par from a fluoro is better per watt than a hps just the falloff is so bad that it really isn't an accurate comparison. A MH still beats both in par per watt though. There.
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http://en.wikipedia.org/wiki/Photosynthetically_active_radiation

Your original statement "a higher watt doesn't give you more penetration" is still wrong. You're now talking about spectrum which has absolutely nothing to do with light penetration.

Also, learn the difference between you're and your. That was painful.

More watts = more lumen which = more penetration.

Photosynthetically active radiation or as more commonly known as spectrum is a completely different ball game. No one was even discussing that. You brought that up.

So sticking to the original context of the thread and your original reply. You are wrong.
 
mr2shim

mr2shim

Well-Known Member
How can you lose spectrum. That doesn't really make sense. If your light penetrates to a maximum of 5ft you're going to get the same PAR at 5ft as you would at 1ft. Spectrum doesn't really decrease the further you're away. That's lumen.

Yes plants need PAR, but explain to me why you will yield more with a 600w than you would with a 250w if the only difference is lumen.
 
Warlock1369

Warlock1369

Well-Known Member
Ok maybe I was to vage. Higher the watts more penetration into the canopy. But as the lumens can go deeper the PAR rating drops faster then the lumens. Affecting the spectrum of light at lower levels of the plant. That is why air to move leaves around and reflective walls are also needed. This help reflect the par spectrum thruout the plant. Going off just lumens isn't correct. It needs to be both. Or corrected with a wide but shallow canopy. Ie SCROG.
 
(818)MedicineMan

(818)MedicineMan

New Member
Just know that a 600 watt puts off almost the same heat as a 1000 watt. I tried a 600 watt out and sold it to keep running my 400's. The 600 in a 5' x 5' sucked. It created a hot zone, both temp and light. I much preferred 2 x 400 watts in that space. cooler with more light. I also have great success with 2 x 400 in 4' x 8' tents.

To each there own.
 
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