glare. I've never had a problem with mine in the 4300-8000k range. Seems to me (in my experience) the higher temp bulbs produce more glare. For fun I have a set of "blue effect" bulbs in mine right now, that would probably equate to a 16-18k or something if you had to put it on a scale, and they have a lot of glare... I'm trying to find my 6000k bulbs so I can swap those back in.