short wave length or high energy light less than 400nm is the biggest concern, and that's really UV / sunlight and LED. if you basement is dark and free of sunlight, short exposure to longer wave length (incandescent, CFL) light is not as quickly problematic as it is over 400nm. however, I and many others do place pillow case or other shield over clear carboy to minimize any light exposure. rule of thumb-no exposure to UV, minimal to CFL and incandescent and you and your beer will be happy.