Distance between light and plant

as close as horticulturally possible. CFL growers will know they got it right when a couple tops get some light burn. EVEN Hids need to be within a foot or so to work right, too many people let their lights sit too far away. Get them lights air cooled and get them crammed into those canopies.

 

It all depends on what kind of light it is, what your temps are, and what stage your plants are at.

 

^Zactly. It isn't an apples-to-apples comparison to learn the distance one grower has his fluoros and another has his 1000w HPS.

 

back of the hand test is what i use.

 

same.. and theres no reasons to ask people because all grows are different.