oh, I forgot to mention that before I've been using just 2 CFL black-lights suspended about 1.5" above my frame. No exposure has been overexposed, and this is with an hour long exposure. So I'm hoping that with 7, arranged in an equidistant pattern with roughly 10 inches between the furthest placed bulbs and suspended about 2 feet above the frame, I'll get reasonable exposures and excellent coverage up to 11x14", though that might be a stretch. 8x10" will be sufficient, though I suspect that our friend the inverse square law will mean that slightly larger formats are easily covered.