I didn’t ask for optimal height. I asked what you run? The reason I ask is I have always ran my height and saw some people running leds at the top of there tent or room. I’m concerned if I ran that height they would grow too fast and I would run out of room.
Shit, my bad. I was sidetracked as I read your post and just replied. My lights are currently 16” above the canopy. Bringing them down a little each day to find the current sweet spot.
many of the images you see of grow rooms with led's are taken at an angle to the grow, giving it the apearance of being far away, it makes the plants look larger then they are
Optimum distance is defined by your light. You can generally get closer with lower wattage lights. A Mars TS1000 (150w) has a sweet spot of around 14". A more powerful light will generally need to be further away. The new bar arrays are an exception as they can get quite close (<10") because the light is spread out over a large area.