Ugh...I screwed up lights math.

When trying to explain light intensity multiple times, I've consistently forgotten a step in the process.

The hard figures I've used as examples have been incorrect, due to forgetting that an inverse square law is relative to the LAST figure involved.

So if you work from industry standard for manufactured lights, initial distance of 1 inch from "source" as compared to an incandescent, fall off isn't at a factor of 324 (you don't divide by 324 to get the answer)...

2 inches is 1/4 of the intensity (25%) of 1 inch. 3 inches, it's lost 1/9th of that initial 0.25 additional (0.277)   4 inches is 1/16th further loss from the 3 inch (0.277 times 1 and 1/16--29.5% losses from the original, so at 4 inches from source, your bulb is approximately 70% as intense, as far as light delivery). 
 
I went off on a member (w0rm), and owe him an apology for making a serious mistake in forgetting to apply what I tried to remind him to apply...standard geometric progression in the inverse. I approached it as a direct geometric progression.


My only excuse is dredging up formula from classes almost 10 years ago, and forgetting a step. Instead of a curve rising to the right, it decreases from the left, in regards to losses.

Outside of that screwup, the gist of what I've been saying is still true....your percentage of loss with each unit of distance only increases by the inverse square

For the sake of those who give a damn about the math, here's a chart of effective light intensity after fall-off. Just multiply your rated lumens by the figure matching your bulb's distance from the plant:



 
2 in 75%
3 in 72.3%
4 in 70.57%
5 in 69.40%
6 in 68.55%
7 in 67.91%
8 in 67.41%
9 in 67%
10 in 66.66%
11 in 66.40%
12 in 66.17%
13 in 65.97%
14 in 65.8%
15 in 65.54%
16 in 65.51%
17 in 65.39%
18 in 65.28%
19 in 65.19%
20 in 65.1%
21 in 65.02%
22 in 64.95%
23 in 64.88%
24 in 64.82%




As you can see, this still means a 1600 lumen CFL is only 1058.72 at 12 inches, while a 32,000 lumen 400 watt HID is 20,742 at 24 inches, so you're still not going to match HIDs watt-for-watt on light intensity (and you'd need 20, not 18, to match intensity), but my scales were way screwed up, and I have to apologize, and put the right figures out there, so folks using the figures I put up use the RIGHT figures, and not my screw-up.
 
 
 
Embarrassing as hell to screw up something that I thought had stuck in my gourd well. Worse to have to step up and eat crow over it.
 
 
 
w0rm, directly to you...you were both right and wrong in correcting me, and I apologize for being an ass about it when I was also screwing up.

 

You're growing with bulbs 2 inches from plant core? Or plant edge?

Makes a difference.

 

I would, too...I've never met ANYONE who hung ANY sort of light so it sat next to the stalk halfway up the height of the plant.

So if your bulb's 2 inches from the plant on the right side, and the plant's 18 inches across, the light is 20 inches from the leftmost leaves. not counting shadows cast by other leaves "stealing" light.

 

PICS!


LOL...I gotta see it...sounds like fun, and I'd be interested to see if you get better "heart yield" doing it.