Abiqua is going the right direction in thought. Think "spectrum", its the reall reason l.e.d's are so cool. No more modified street lamps hovering in heavy contraptions above your meds.
Actually, I preach photon delivery and raw amounts, that is efficiency in a nutshull, how much and how well does a light source deliver it....Spectrum alone is a dead horse....THE HPS is considered a terrible "spectrum" in consideration to a source like the sun, but it has been the standard for 25+ years because it delivers monster yields....
The diodes I use [Cree CXA and Bridgelux Vero] emit about twice the amount of useable light
watt per watt as ANY Mars fixture and costs about the same or less to build the fixture....until recently, these diodes weren't available and are barely in any commercial LED fixtures...and as people educate themselves and rely on the knowledge base here, they start to realize this potential...
@Tim Fox was one
That's why I cringe with these threads sometimes....the Mars users who are killing it, could be slaying it with Good tech.....I went from poor/medium tech averaging 350ppfd roughly and still managed .7 gram/watt across all my strains...Doubling my PPFD has not only increased my yields [still in early stages, but been pushing 1.1-.2 grams/watt across all strains, but it has also changed my plant characteristics in general too...ie. fatter stem growth is much more noticed, stretch, etc etc.
Spectrum can indeed be tuned but I have never noticed the effect of switching from say 2700k to 4000k in flower compared to doubling your PPFD. Raw power
seems to be the grail...I worry about delivering it as efficiently as possible and smile when I notice it is tipping north of what the best HID lights are doing, watt per watt.