Hey man the lights have been ABOUT 18 inches from the top of the canopy for the entire grow. I'd say 20 inches between the light and the plants when they were seedlings (days 1-7) and right now it's at about 16 inches for the plants finishing up. The area51 website have a 18 inch distance as their recommendation. Same distance in veg and flower mode. I had some plants as close as 15 inches from the light for a few weeks with no adverse effects (like bleaching). Seedling definitely seem to prefer 20-24 inches. Good luck and I will be updating my journal soon so check it out sometime. Peace.