BTU AC per 1000w cob?

its independent of distance its average ppf over an area.is your area larger at 18" than at 12"?

George2324 said:

For every 12 inches away from the plant the usable light drops by half.

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Not quite. The inverse square law says when you double the distance the intensity falls to 1/4. But that is from a point source radiating 360 degrees. There are other factors that distort the inverse square law - mainly reflectors and optics. So there really is no one hard fast calculation that covers every light.

Now, as to more distance equaling more penetration, the concept is this - Lets say with a given optic/light combination you get 1000 umols at 12 inches, and the fall off is 50% lower at double the distance, 500 umol at 24" - you have good penetration for about a 12". So now if you increase the intensity (while keeping optics the same) so you get 1000 umol at 24", your fall off rate will still be 50% at double the distance - which is now 500 umol at 48", instead of 24" - now you have 24" of good penetration.

CobKits said:

its independent of distance its average ppf over an area.is your area larger at 18" than at 12"?

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I have 4 cobs for every square foot.

What I think you mean is do I have more space below the cob than the actual cob takes up?

Then no I literally have so many cobs per square foot that I could have the plants 4 inches away and probably have very even coverage.

They are mounted on 28cm diameter heat sinks

Equally spread apart