I have pushed as many as 16 5 gallon pails under a single 400 watt HPS and got a nice yield, 16+oz.

I am a smart guy and an electrician for over 40 years. So I tell you, watts is good for comparing light sources of the same color and type. But some types of lighting is more efficient. Thus, a 400 watt LED will provide more light and if the color is optimal, the LED will outperform an HPS setup, an HPS will outperform a florescent and a florescent will outperform incandescent lighting. This data is called watts/ lumen based efficiency. Lumens are not the best criteria scale for plant growth though. Plants use energy of specific wavelengths (color). The Kelvin scale used for color is an absolute scale. Meaning the zero is actually absolute zero, the point where no molecular motion occurs (something like that). As a conversion, room temperature of 68º F = 20ºC = 293K +/-. The color is the radiation given off by heat. When you see metal in a fire glowing red to yellow to white hot what you are watching is the visible light radiation and we humans can tell these temperatures, to some degree. Hot metal shows us the temperature. A match is around 1700K (a red/orange color). We see a 'warm white' (yellow) glow of our old incandescent lamps the temperature is probably somewhere around 2700K, just like the color of warm white CFLs. Moonlight is around 4100K, this is a common florescent 'cool white'. Super hot 6500K (hot white) like molten metal or natural daylight this, the florescent tube color 'Daylight'.

ttfn :stoned:
Shovelhandle Reviewed by Shovelhandle on . Lighting is a different language to me... All this lighting controversy is driving me insane, I can't find out of all the threads I've read useful information, it's like trying to understand college calculus!! So far what I do understand is the type of bulbs t5 t8 ect. But I have no idea about kelvin, or his damn friend lumen, or the measurements for their grow space. So far I've been reading, an just hearing users trash talking not so much debating. So here's what I'm asking. Rating: 5