well not too sure cuz i wouldnt waste time researching ti (im into stealth n budget grows cuz im a broke ass right now lol)
but i heard the sun gives off 10,000 lumens and the minium is around 5,000 and is u can grow a 6 foot plant outside that thats 10,000 lumens then id say maybe do 10,000 lumens worht at the tops and add maybe 1-2 cfls that give off atleast 2,000 a piece on the sides for under growth and side growth id say anything over 15,000 lumens but i dont think u can kill a plant with too much light if u have the temperatures not high and the light bulbs not too close i dont think nothing can happen:/ not sure tho never thought about it id say just dont go over 15,000(10,000 for the main colas and tops and 5,000 or so for the side lighting to promote the side and under buds to grow too
hope this helpd
Tha Dope Man