A question, I've been pondering for a while, for you to consider:

Background:

Let's say that our one thousand watt HPS puts out one hundred thousand lumens (probably low but I like to keep things simple)

By definition lumen ratings are based/taken one foot from the source so (according to that inverse square law thingy), at twice that distance, two feet from the source, the lumens drop to twenty five thousand lumens. (one divided by (the inverse thing), two feet (twice the original distance from the source), squared (four) equals one quarter or twenty five percent, a loss of seventy five percent at twenty four inches. At three times the distance (three feet), there are 1/9 lumens or 1/(3 squared) for a total of eleven thousand one hundred eleven lumens.At four times the distance (four feet), there are 1/16 lumens or 1/(4 squared) for a total of six thousand two hundred fifty lumens, etc.

Now for my question, what happens when you move closer to, rather than further away from, the source?

Let's say I have eighteen, sixty-five watt CFL bulbs (total eleven hundred seventy watts going in, slightly more than the example above) rated at thirty six hundred lumen each, for a total of sixty four thousand eight hundred lumen.

Now, if I move these lights to six inches from the plant (one half the distance at which lumen measurements are taken), would the formula then be the same only with a distance halved instead of doubled, tripled, etc.?

Due to the definition of a lumen, I cannot decrease the distance between the source and receiver below one foot and still call it a lumen. Or can I?

In this case the math indicates that at six inches(1/(.5 X .5)) X lumen rating, my sixty four thousand eight hundred lumens are equal to two hundred fifty nine thousand two hundred "perceived" lumens. Wow, I gotta be wrong somewhere, how about it guys?

Let's see what happens (if my assumptions are correct) when the bulb is three inches (1/4D) from the plant... Wow again, sixteen times the rating equals one million thirty-six thousand eight-hundred "perceived" lumens.

What an I doing wrong here? Anyone?

Id imagine that where they measure from is just at the distance where the lumens begin to diminish from their full conecntration. So I guess it would be as simple as that it doesnt work the other way around. *shrug* thats my 2 cents.

You can go as close as you like. The plant will manage it IF;

*You're environment is right.
*You have the lights cooled properly so there is no radiant heat building up around the plant.

Apparently a water cooled 1000W light can be fucking humped by a plant since it's so cool.
However if you blot all the sun, you'll get a few real good top colas, but the rest of your plant won't get shit.
You'll also really diminish the potential canopy size.

First of all huh?

Just for argument sake lets say your light is a 1000w mh producing 100,000 initial lumens. Key word is initial. That means right at the source the bulb is producing 100000 lumen. So if your plant was touching the bulb it would be getting all 100000 lumen. For every foot away from the bulb you lose half of the lumens. Plant 1foot away recieves 50000 lumen, plant 2 feet away recieves 25000 lumen, plant at 3 feet receives 12500 lumen ect. So at 6 inches it would be 75000 lumen.Natural sunlight is aprox. 7000-8000 lumen. You can never achieve more lumen than what your initial source provides, you can't add lumen. Eg. 2 bulbs producing 100000 lumens each is not 200000 lumen. 10 cfl at 2500 lumen is not 250000 lumen, it's still only 2500 lumen. Hope this helps.

Cheers GG.

Hey everyone, I found my answer and my thinking was correct

At 1/2 the distance, six inches, the intensity is multiplied by four times. At 1/3 the distance, four inches, the intensity is multiplied by nine times. At 1/4 the distance, three inches (well within my range), the intensity is multiplied by sixteen times. This means that a single sixty five watt CFL putting out thirty six hundred lumen at one foot, puts out fifty seven thousand lumen at three inches, and I've got twelve bulbs, so that's six hundred ninety one thousand two hundred lumen total!

Please take a moment and watch this. Rad 7 Inverse Square Law

All though this example is for radiation, another form of light, and is measured in rems, which are based on a point one meter from the source, the same law applies to lumen, based at one foot from the source.

Now I'll go fire one up and shut up for a while...

Sorry for being a jerk...

first off I don't want to join in but all I read was a 65 watt CFL that puts out 3600 lumens initial lumens somehow puts out more lumens than a 430 watt HPS.

How do we know that the initial lumens on the package 3600, was measured at 12 inches from the bulb? I would imagine that the way the lighting industry measures initial lumens shouldn't be different from a HID to a CFL. So where is the initial lumens really measured from is my ?

and I'm sure everyone knows that plants don't use lumens, it's all about Photosynthetically Active Radiation which was where your link led to radiation but hats off for some research though

agreed guys and also id like to add ..do not trust the light pyramid..it only really applies to an empty room...get it? light is trapped and diffused in the canopy and foliage..that is why i light from on top, sides and within the plants...some might say it is to much...all i can say is to better utalize what your using and you will see the diff in final weights.
want a better understanding? draw a light pyramid draw plants and then draw lines bouncing up and down from reflector to canopy do the same thing on the sides and you will understand how the light can get diffused and basically works.it is the simpleton way of doing it but you will understand it much better.just by seeing your dark areas in the corners of your room should be a good indicator your not using the full potential of your space..not to be a "better than" but i have no shady areas in my space and "imo" it is being utilaized to its full potential. buds soil to canopy no popcorn at all.peeps who have been in the same exact space for years have learned to tweak that space to its maximum potential. it all starts with the basic understanding of your space.

I think this point is being overlooked also.

I understand what he is talking about but growing under cfl's when compared to the hid family is like trying to grow outside with a canopy over your garden with holes in it. Photosynthisis, lumens, and intensity are all still there but only for a little area under the hole. The rest of the garden suffers.

Sadly all the research in the world does not hide the fact that the hid family has no real competition yet.

Remember KISS?

Hey 1952HD, you read my ridiculously long posts in that cfl grow thread, I want to get into that briefly if I can. You wrote that "I seem to understand it", referring to the inverse square law. What did you think about my mention of a modern car projector headlight? Do you dispute my claim that the inverse square law is not applicable to that? Do you dispute my claim that with any type of reflector, the inverse square law does not strictly apply?

We're looking at this almost the exact opposite way. You're looking at lumens and distances between the bulbs and plants, with no mention of reflectors, I'm looking at wattage vs plant surface area, and trying to design an overall system that will get the light to the plant the best way.

If you want to see a pic of my setup with the reflector walls, it's in the hydro section, "dwc setup, couple pics".