This entire discussion confuses me. I've been using a simple
fluorescent ring lamp (built into a desk magnifier unit) for my
exposures.
The ring lamp provides nice even illumination. I place it 15-20cm
above the board. 7-10 minutes exposure and I'm good to go.
Then I use the magnifier to inspect the board when it's done :-)
The one I use looks like those on this page:
http://www.tooldigger.com/f/Fluorescent_Light/