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Do Watts Matter?

Do watts from the wall matter? The old rule of thumb was 25 watts per sq ft was the minimum for flower. Now most of the new LED's seem to hit right at that target for flower but they are not much above it. When we measure light at the top of the canopy we dont measure in wattage we measure in PPFD or LUX and raise and lower the lights to hit the target PPFD or LUX balanced across the canopy. 

With 2 1000w HID's over a 4 X 8 area I have about 62 watts per square foot, that's over kill but by raising, lowering and tilting the the lights I can maintain a even light canopy at about 40,000 LUX at the top of the grow canopy for Veg and 65,000 LUX  through flower from corner to corner. Looking at the SF2000 LED as example in the center at 18 inches above the canopy it has a rating of 974 PPFD in the center and as low as 437 PPFD at the outer edges of the light canopy. In a 2 X 4 tent with the light at 18" the light canopy intensity decreases by over 50% from center to corners. I put a light mover on mine as a test and the light is more balanced but still a long way from a level canopy.  

So wattage may play a roll in the PPFD but not as an equal size area.

is it possible to have a flat canopy of light with an LED? If so how?

What are your thoughts on that? Please let me know so I can stop thinking about it.  

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Replies (13)
  • I think you would have to have multiple lights. I'm only on my 2nd grow with this sf 4000. Wasn't impressed with the first 1 if compared to hps! I would have thought the light mover would have helped for sure.

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    • I was not impressed with SF2000 when I compared it to the Viperspectra 700par I have been using in that same space, I was hoping for it to kick ass so I can replace the 1000W in the grow room. The light mover seems to be working as far as the light meter readings go but the final proof is weeks away. No way will it cover the 2 X 4 footprint in flower like they claim if its stationary. 

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    • what kind of a pain in the arse was the light mover to install, and if ya don't mind me asking how much it was.........

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      • Actually it was easy, I was able to slide the rail between the light hanging cross members in the tent and the top of the tent and its secure as hell. I bought a cheap mover for testing, $110 I think it was. It has a dwell at each end from 60-120 seconds, if I buy one for the grow room I will want one I can control the speed on. 

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      • Guatemala Robotics out of Colorado have great movers, and great service too.

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        • Thanks

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        • @ CPW The 4000 will cover a 4x4...I'm growing in a 2x4 flood tray...Thanks for the info Chubby...

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          • @Rick, Yes it will cover a 4 X 4 area but the PPFD is not enough to make good buds. Actually it looks like it would be ok for a 2 X 4 table. I was wondering how you got that light in a 2 X 4 tent. So much of LED's are magic from what I know, lol

            My understanding of LED's is you need 600-1000 PPFD to get what the buds need, and my first grow showed that to be true, hopefully the light mover is going to boost that with the SF 2000

            If any of you LED guru's can show me I FOS, I truly do want to know

            Spider Farmer SF 4000 PPFD MAP

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            • I have asked that question to SF, HGL and Gativa with no response from any of them. 

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            • I have been debating over LEDs and specs, it's all to much to choose from, so I just bit the bullet and got a light that is 640w 8 bars Samsung's 301B, 301H , Osram , all the usual, it's was listed at £500 knocked it down to £450, it's a Chinese made but I don't care if it covers a 6 X 6 veg and 5x5 flower I will see if I can get the specs to see if it helps you, I will be testing it in the next few days, 

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              • I can only run my 4000 @ 50% or it will be well over 1000 ppfd. I don't use a tent. Sry guess I missed your posts. 1000 ppfd is max, it's actually a lil too much unless you are using CO2. (in flower)  500 ppfd is max in veg. And my light is 32"+ above my canopy. Hope anything I said helps.

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                • Yes it helps, we seem to be on the same page. I think you could cook a turkey under the center on some of these lights. The key seems to be finding the balance I guess

                  thanks o

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                • I ran mine @ 800 ppfd in the center and the ends settled @ 500 ppfd...And the only way you can have a even canopy is by training of your choice in the fight places. Sounds kinda a pain to me. Strains can help. Stretchy strains on the outside and the shorter bushier ones in the center. See wtf you have done. I been sitting here contemplating all this shit to for over an hour now. So I'm gonna try and stfu now. cool

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