1. I built my own light source using BL 18 inch bulbs. Spacing was as close
as I could get the sockets. Pretty close since you have to take the outer
bulbs out to get to an inner one. The unit was designed to sit on a bench
with the bulbs facing up. I originally put the print frame on top of the
bulbs. This worked well up to 8 x 10. When I got around to 11 x 14, I
suspended the unit upside down from the ceiling using chain and "S" links
so I could easily raise and lower it. Now the unit shines down over a
bench. The print frames are raised and lowered using wood blocks and
cardboard boxes of various sizes.
2. When I am using a copy stand, I use an incident light meter to check
the uniformity of the light on the work I am copying. You could use such
a meter to check the UV light source for uniform light distribution. I have
never done this because I have never seen any evidence of it in my prints.
FL tube are pretty diffuse sources. My light source has an aluminium panel
behind the bulbs that I spray painted white which also helps diffuse the
light. The unit is about four years old and has been used for gum, cyanotype,
salt prints, platinium, paladium, VDB, kallitype, albumin and chrysotype
by myself and my students, in other words, lots of prints by lots of
people. No one has ever complained about nonuniform light density. If I
can't see it and my students younger eyes can't see it, I'm not going
to worry about it. I might add that if you do use a light meter to detect
slight variation in light density, what exactly would you do about it?
Bob Schramm