hope this helps some
[video=youtube;hx2ZWw00c9Q]https://www.youtube.com/watch?v=hx2ZWw00c9Q[/video]
It's time to learn the Inverse Square Law about lumens and light penetration depth.
1 foot from light source = 100% illumination and LUMENS
2 feet from light source = 1/4 as bright
3 feet from light source = 1/9 as bright
4 feet from light source = 1/16 as bright
The Inverse Square Law ( ISL ), basically states that your plant will receive 100% lumens IF it's within 1 foot of the light source.
For every ADDITIONAL 1 foot of distance AWAY from the light source, lumens and therefore canopy penetration diminishes GREATLY !!!
Please keep in mind that those utilizing a glass lens in an air-cooled hood/tube of ANY kind are NOT getting 100% lumens because of the glass lens.
For the purpose of simple division, we'll use a light with an output of 100,000 lumens, which is roughly 10,000 MORE lumens that the average 600w HPS and roughly 40,000 lumens LESS than the average 1,000w HPS.
1 foot within light = 100,000 lumes (100%)
1 - 2 feet from light = 25,000 lumens (250w HPS roughly within 1 foot)
2 - 3 feet from light = 11,111 lumens (125W CFL roughly but less than 150w HPS within 1 foot)
3 - 4 feet from light = 6,250 lumens (250w HPS @ 1- 2 feet from light)
So as you can see, the drop in lumens and how much light penetrates your gardens canopy drops significantly with every 1 foot of distance away from the light source.
At 2 feet away, my 400w Hortilux (55,000 lumens) pretty much hits like a 150w HPS, and anything below that gets trimmed off (popcorn buds).
