the OP's title and comment in his first post is aimed at the PDF he linked to..........the PDF is the reason this thread exists and should be what we discuss not" whats the best bulb?"[like rusty i use the cheapest] or "when/will HID's be outdated?[only HPS/MH in my room for now]. I do not seek 1% more THC 2% more CBD's or 8% more trichomes but knowledge and information. i already know that UV can have beneficial affects on some verities of cannabis. i also know that it can be useless on others and dangerous to work with:beatdeadhorse: ........................this is what i consider " on topic" Rusty " I believe the yellow spectrum is absorbed and converted by the chlorophyll B pigments, but would have to double-check."THANKS RUSTY . could any of you LED growers blast a bud with some yellow during flowering to see if it makes a difference in cannabis ?