Hey, I bought 2 600 watt hps lights from htgsupply about a month ago, and placed my 5 foot female about 9 inches below the light. Two weeks ago she started showing UV burn spots. I have since raised the light to about 20 inches or so. I can’t go any higher now; the light is as close to the ceiling as it will go.
Also, there’s no safe way to attach a UV absorbing glass plate because I bought the light with the cheapest fixture to save an extra 80 buck or so per light. I never consider the UV radius which seems to be about 12 - 14 inches for 600 watts.
I may be okay on my current grow, because I’m not going to allow them to grow to 3 feet before flowering.