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froggy · #4 (**permalink**) 06-30-2006, 01:11 PM

u will get 4-6 plants under a 400w light. i do 4, i suppose u could maybe do 6 if they are of different ages but 6 tops. 6 plants / 8 weeks of veg = .75 plants harvest per week, not ur original # of 3-4. and frankly i think im being generous with that #. ill bet if u ave. over the year, ur under .5 plants/ week or a better gage of less than 1oz per week.

this is from experence. i find that a # of around .5g/watt/harvest is all the better u can do with a 400w light. there is a physics reason for this. its called the inverse square law. http://www.intl-light.com/library/ca...s/inverse_calc

the 600w and higher lights have deeper light saturations. these # work out well for growing indoor because of the hights of the plants vs position of the light. i can get .7g or more/watt/harvest with a 1000w. g/watt/harvest is the true measurement of ur system because all things are equal except the wattage.

by the way, .5g/w/h is when ur system is going well. any mistakes and that # goes down. heat/water/vent/bugs/etc and that # goes down. so lets say u get a 25% lowering of yield because of heat stress. that means the .5 goes to .375g vs my .7g goes to .525. what i mean is that the overall #'s are going up with a larger light also because of that inverse sq #. so i can have a bit more inefficency with my 1000w lights and still have a respectable output, ie its more forgiving.

again, ill repeat myself by saying that i find that if i have 400w of veg lighting, that amount of light can support 1200w or so of flowering light. im not sure what other find but that is what my #'s work out to. so if i have a 400w flowering light, i only need about 150w of veg lighting to support that amount of flowering light. 2 shop lights are 160w, which would be about right for a 400w HPS.

lastly, if the plants get too tall, the inverse sq law factor gets worse and worse. if u are going to keep the 400whps, then get some plants that dont wanna grow tall. certainly a 2.5 tall plant at maturity is about all that light can handle. maybe a nice hashplant or other compact is in order.

#4 (permalink) 06-30-2006, 01:11 PM
froggy Old School Stoner Join Date: Sep 2002 Location: way north of u Posts: 1,363	u will get 4-6 plants under a 400w light. i do 4, i suppose u could maybe do 6 if they are of different ages but 6 tops. 6 plants / 8 weeks of veg = .75 plants harvest per week, not ur original # of 3-4. and frankly i think im being generous with that #. ill bet if u ave. over the year, ur under .5 plants/ week or a better gage of less than 1oz per week. this is from experence. i find that a # of around .5g/watt/harvest is all the better u can do with a 400w light. there is a physics reason for this. its called the inverse square law. http://www.intl-light.com/library/ca...s/inverse_calc the 600w and higher lights have deeper light saturations. these # work out well for growing indoor because of the hights of the plants vs position of the light. i can get .7g or more/watt/harvest with a 1000w. g/watt/harvest is the true measurement of ur system because all things are equal except the wattage. by the way, .5g/w/h is when ur system is going well. any mistakes and that # goes down. heat/water/vent/bugs/etc and that # goes down. so lets say u get a 25% lowering of yield because of heat stress. that means the .5 goes to .375g vs my .7g goes to .525. what i mean is that the overall #'s are going up with a larger light also because of that inverse sq #. so i can have a bit more inefficency with my 1000w lights and still have a respectable output, ie its more forgiving. again, ill repeat myself by saying that i find that if i have 400w of veg lighting, that amount of light can support 1200w or so of flowering light. im not sure what other find but that is what my #'s work out to. so if i have a 400w flowering light, i only need about 150w of veg lighting to support that amount of flowering light. 2 shop lights are 160w, which would be about right for a 400w HPS. lastly, if the plants get too tall, the inverse sq law factor gets worse and worse. if u are going to keep the 400whps, then get some plants that dont wanna grow tall. certainly a 2.5 tall plant at maturity is about all that light can handle. maybe a nice hashplant or other compact is in order. __________________ froggy For as long as space endures, And for as long as living beings remain, Until then may I, too, abide To dispel the misery of the world.