This is my light cabinet. I have two sets of lights behind the diffuser panel.

The first set of lights consists of four screw-in incandescent bulbs on their own dimmer switch, spaced equidistant behind the diffuser. I recently installed Verilux 60 watt "Purity" light bulbs, which produce a more natural spectrum of light, and rated to last 5000 hours.

I also have four 24" fluorescent fixtures with 5000k lights, mounted horizontally. These are on a separate switch from the dimmable lights.

Most of the time I just use the incandescents, dimmed to enjoy my insulators without being glared out of the room. I fire up the 5000k lights when I want to closely study my insulators.

I chose the Verilux bulbs after a failed attempt to use dimmable compact fluorescent (CFL) bulbs. I abandoned the CFLs because they made an audible electric humming noise. My light box amplified the noise like a speaker cabinet. It was intolerable. I don't recommend dimmable CFLs!

In this photo, only the incandescents are lit (to maximum illumination).