I'm going to quote Ibechillin's post in the thread "Do you measure PAR for your grows?" yesterday.
"[FONT=Arial, Helvetica, sans-serif] Bruce Bugbee mentioned in his lighting myths video cannabis can utilize more than 43.2 DLI typically regarded as most productive but spectral ratios have major influence on plant utilization....[/FONT][FONT=Arial, Helvetica, sans-serif]500 ppfd under 3500k led with minimal IR is roughly 30k lux and with adequate overhead diffusion to reach deeper into the canopy (or additional side lighting/under canopy lighting to stimulate lower leaf chloroplasts) people have claimed 2gpw. This is also approaching the "theoretical" max ppfd plants can tolerate at atmospheric ~400ppm CO2 availability."[/FONT]
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Yeah, diffusion and side lighting are good. A leaf cannot absorb an endless ammount of light and it's better to light more of the plant.