The reason I do not blush to tell you I'm not following this theoretical
discussion is because, as is well known, theoretically the bumblebee
can't fly.
Still, I'm surprised to find "circles of confusion" (which I once
understood *perfectly*) applied to contact printing. Aren't the optics
different?
Meanwhile, theoryless, I have been running some tests -- identical
emulsion exposed simultaneously by the nuarc and by fluorescent bulbs
(about 1 1/2 inches from bulbs to paper, bank of seven 24-inch BL bulbs,
touching). My initial (and so far most definitive) finding was that the
aluminum foil I had wrapped around the base of the fluorescent fixtures
(as per an authoritative text which shall here be nameless) was destroying
definition. The foil removed, I find (so far, and so far as I can tell)
the *steps* are equally crisp with both light systems, but the numerals
look softer with the fluorescents. (That's the numbers on each step of the
21-step as well as the lettering at the top). I tentatively attribute this
to softer contact -- I don't have a vacuum frame for the fluorescents.
(I have somewhat improved contact by sandwiching between two sheets of
plate glass and removing a paper wrap on the top glass, but not enough.)
I'll try to rig up vacuum frame with the fluorescents for a test, but
meanwhile another finding suggests I may abandon them for gum. I haven't a
clue why, but the limited tests I've done so far show that the pigment is
richer and shadow steps deeper with the NuArc. Does anyone have a theory
for that?????? (I have found no difference with cyanotype.)
> Is it possible there's some difusion going on in the paper itself?
> Perhaps > the light is even bouncing back up into the sensitized portion
> of the > substrate after being reflected from the back of the printing
> frame. Does
Are you suggesting that the diffusion "in the paper itself" would vary
according to light source?
> possible the lack of sharpness is caused by the paper fibres swelling on
> wet processing and not necessarily drying down with a 0.15 mm point
> perfectly resolved in exactly the same position? It might be worth
Again, I'm confused here..... presumably the fibres would swell equally
during wet processing regardless of light source.
Good grief, you've got me doing it -- I mean *fibers*!
I'll try a black backing for the test with the fluorescents, perhaps it
does make a difference -- I've been testing on thin paper.(The NuArc has
a black mat.)
Be careful outdoors, Philip......a lot of cosmic rays going around.
With the windchill factor it's 19 degrees fahrenheit here tonight. Sure
glad I don't have to risk dangerous radiation from sunny skies.....
Judy