lighting/math related question

[TroubleGuy]

Just wondering what methods there are to calculate the optimal light space for lights...i'm sober and not thinking great so I might not explain this well. Watts psf means nothing to me - the intensity of the light dissipates the higher the lamp is from the canopy so this is not an accurate way to measure.

I have a 1000w operating and bought another 400w to add to it. I want to make sure it's used as efficiently as possible to maximize usable light, and by that I mean usable INTENSE light, not raising the lamps to light the whole room at the expense of light intensity or putting plants 4 feet to the side..

What I'm trying to do in a SoG grow, is start the plants under the 400w and gradually move them over as needed each time a new geneation is added, to finish their life under the 1000w. I'd like to make use of the overlapping light, which is why I'd like to be able to calculate this stuff, I really don't want to be making unnecessary holes in the cieling by moving the light's position a bunch of times and would like to get it right the first time.

If that didn't make sense just ask questions, having a hard time thinking straight/clearly today for some reason.. thanks.

 

[TroubleGuy]

done a little research... a 1000w lamp at 4 feet away gives about 10,000 lumens. At 3 feet it gives betwen 15,000 and 16,000...

What's the math behind this? How do they determine these numbers?

I'm looking at page 179 in Cervantes' grow bible and it states in a 4x4 room there is 62.5w psf as well as the 10k lumens @ 4 feet thing. I'm just trying to figure out the math behind this so I can deliver at least 50w psf and 10k lumens to every plant in the farthest parts of the room, more to closer plants obviously.

 

[niacinamide]

What's the math behind this? How do they determine these numbers?

Illumination from a point source such as a filament or arc lamp follows the inverse square law. Illumination is computed by light intensity at the source divided by distance squared.

 

[purpledomgoddes]

http://www.icmag.com/ic/showthread.php?t=109201
figuring watts per square foot in vertical

http://www.icmag.com/ic/showthread.php?t=108993
lighting conversion data

w/ 1k's, no cool tubes, lights get 3-6" away from bulb. would get them closer w/ 400's/600's; maybe 1"?

only limitations w/ closeness to light(s) are cool+constant air flow over canopy.

would never place a 1k further than 1 foot away from plant; even >6" seedling/cutting. @ 6+" they get ~6" away. @ a foot tall they get as close as they can be placed. 2-6" when mature.

re-post from thread(s) ^.
actual formula:

n=desired light level in lux*surface area/effective flux[lumens]

where n is the number of fixtures required to achieve desired lux

example: 9'x128'(252 feet of area) table-area over which 400w hps' will hang. light intensity of 8600 lux(800 foot candles) is desired.
effective flux(lumens) is ~38,400 lumens.
the number of fixtures is equal to the light level times the surface area to be lighted divided by the effective flux, or

(800*9*128)/38,400=24 fixtures

the fixture pattern is defined by the horizontal spacing and the height above the crop surface (or, in this case, the concave curvature of the imaginary 1 ft circumference around the 1k hung vert).

the light level is equal to the effective flux divided by the area, or,

e=f/a [and, therefor, a=f/e]

where e is the light level, f the effective flux (lumens), and a the area

hope this helps.

 

[TroubleGuy]

Got the airflow covered but no cool tubes. It's at about a foot off the top of the canopy right now and it's warm but the fan keeps air moving so nothing burns.

Thanks for those links, I'm gonna sit down and have a look once I get some work done tonight.