This is what I always preach, good topic. I have my 400 about 4 inches away from the little ones in veg with an air cooled and with the air cooled on the 1000W I go about 10 inches, I could go closer, but I don't want to loos the ft print and I have noticed that some plants can't handle the lumen intensity and the chlorophyll in the bud will become bleached and turn white.
Adieu
BlueBear Reviewed by BlueBear on . Light intensity: Why to keep lights as close as possible Light intenstiy = Total Light Emitted / ((4 x pi) x (radius^2)) And light intensity decreases by 1/x^2 where x is the distance. So like if you have 135,000 lumens at 1 foot, you increase that to 2 ft, you it would be 135,000 x 1/2^2 which is 1/4 so basically one fourth of 135,000 = 33,750. Add one more foot, 135,000 x 1/3^2 = 135,000 x 1/9 = 15,000. Crazy huh? Thats why the top bud always is so big and the bottom ones are smaller, cause they get a lot less light. LST'ing takes that Rating: 5