John, I'm intrigued by that "one-eighth inch apart," which I assume means
you have separate ballasts. My engineering skills don't reach that high
so I settled for butting ready-made strips together, which makes the
bulbs about 1 inch apart. But don't you have trouble changing bulbs? I
thought you had to have room to get the fingers in there.
However, what I'm really wondering is about the one-inch distance to
paper stage, which raises 2 questions:
1. Have you found a good way to test for hot spots? The best I could come
up with was a weak cyanotype coat (cut with water) on paper the full size
of the paper stage with a brief exposure,say 1/3 "normal," to see if
there were differences in the blue density. (When you give full exposure
tendency is for the emulsion to max-out & hotspots disappear.)
2. Aside from speed and so forth, is the 1-inch distance maximum for
sharpness? Last year in these pages Mike Ware cited some square of the
sugar cube law that I didn't follow, but his hypothesis (at least at the
time, at least as I understood it), was that a 3-inch distance from the
light bed to the paper stage would give the sharpest image.
An optics mavens on the line?
Cheers,
Judy