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Gavita looks interesting. 345W consumption. Bar style 1100x1100 to be mounted at ~ 200mm. It's surely aimed at the 1.2 giving about 20w of LED per foot.
SPYDR do a comparable light, but feel to reach a good DLI, you need to do auto's as 12 hours light isn't enough.
Perhaps 20w is still for plants in veg. Though it's going to be strong growth.
40 in bloom gives me upper wilt, unless supported with co2. That's well spread lighting, hung around 350mm
Depends on the light efficiency.
Leaving out the corrections and just roughly compensating.
Without co2 max will be about 900ppfd (like that's pushing pretty hard in flower 12/12)
So you want a light that can reach that.
Say scorpion Diablo 2.9 ppf/w at 650w
2.9x650=1885 ppf (m2 is how that's measured so about 10.75 sqft)
So we take our goal of 900ppfd and divide my 10.75 = about 80ppf per sq ft.
So now that particular fixture is putting out 1885 ppf and we divide by the 80ppf per sq ft we want.
1885 ÷ 80 is about 24 sq feet. So a 5x5 perfectly without co2.
Now take a cheapo LED and maybe it's 2.1 ppf/w and equal wattage of 650w
2.0 x 650 = 1300
Now we want 80ppf per sq ft again so
1300 ÷ 80 = roughly 16 sq ft so you now only can properly flower a 4x4 with the same wattage.
This is why efficiency is so important and why some experience different watts per sq ft needs.
The first is 27w per sq ft.
The second is 40w sq ft.
Now these number are pushing a plant very hard without co2 and most won't be running those numbers but it's a safe bet when buying that you will have more than enough light to properly flower.
The exception is when you add co2.
Understand this was just a blab shirt version without compensating for light bleed, true ppf etc. But you don't need to be much closer than a roughly guide when buying as long as your reaching 700-900ppfd you have plenty of light imo.
Edited for math.... ran out of crayons
that KS for the heads up
@growsince79