havent really taken a measurement lately but im gonna say about 24 inches using a 1000w bulb, its on a digital ballast that i can bring down to 600w cant get room temp any lower den 80f and dont have no room to move light until i move my grow room else where!Holy cupping margins! Yessir...the cupping means heat burn. Back of the light unless its your poor ventilation causing heat buildup. How close is your light and what type of light is it?
thank u gonna work on dat later on todaylight should be 30 to 32 in away...get an a.c in or right outside the grow room. ur stuff will grow faster at 75 degrees or so