Robertsanswered grow question 3 years ago Or go purchase one of those cheap green 4 in one soil testers. They have a light sensor that works fairly well from my experience. The rest of the tester is junk. But that part works. With a SF-1000 right now I am on 100 percent at 12 inches. In my Thc bomb auto diary. Monster plant for little light. So with it being bigger in flowering about 15 to 16 inches at center point would be max distance. I personally don't dim my lights for seedlings. I place plant farther from light. Keeps grow area warmer. Good luck and happy growing 🌱