Re: Sources for stochastic screens
Small world. That's neat Chris.
Elizabeth Dove's page is very informative, but she doesn't list the
specs of her screen (dpi, density, etc.) and only says that it works for
Photopolymer and ImagOn. I'm sure it does work, but filtering through
the specific imagesetter screens I know David Hoptman has tried and the
some dozen screens I've tried, I've come to want a more info. Is it any
different from the standard aquatint screens one can buy from Graphic
and Chemical or Dan Welden? Too coarse and the dots become apparent,
too fine and the plate breaks down too easily when cleaning... I
believe I've found the happy medium for the way I work in choosing the
1800 dpi screen, but I'll be interested to see how other approaches work
out for people and learning more details about them.
I too got wildly diverging exposure times for image/screen early on. I
think it has to do with the relationship between the screen and the
image I described in a posting a last week where the image actually
contributes to the "aquatint" in a somewhat unpredictable way. I'd get
an image that looked ok, but it wasn't quite "right" and with not much
latitude for tweaking. Ultimately I went with the relationship closer
to, but not exactly 50/50 image/screen time.
Super-damp paper (glistening) might lead to patches like what you
showed, but unless that's the case, it sure looks like general contact
issues and/or the weird problems I've described related to UVBL bulbs...
Regarding curves...when using solarplate and coarser screens I do start
out with 100% mapped to about 82%. With the KM73 curve I developed
along with the 1800 dpi screens -- I don't - I start with 100% being
100%, but drop off drastically from there. This is because I believe
the finer screen can represent more shades of grey without needing to
compress the curve as drastically as one does with solarplate or imageon
and the coarser screens.
Again, I'll post when I know more about this source I found for the 1800
dpi screens. I'll need to update the sources list on my website in any
case if Copygraphics isn't going to be able to deliver the goods from
now on... :-\
Jon
Christina Z. Anderson wrote:
Well, Jon, I have a funny--last night I checked out Keith Taylor's
aquatint screen source, Elizabeth Dove. Come to find out she lives in
MT! And teaches at U of M! Our rival :)
So I ordered one last night, and even funnier, she emailed back and
said, "This is weird, on a friday night I get two orders for these
screens, which I don't get much, wonder what is going on?" The other
order was from a guy in TX.
I told her there was a post to the alt list about her and that Keith
was a blabbermouth, heheheh. So there's one happy woman and another
reason this alt list is so wonderful.
I've been rereading every text I have on solarplate--Keith Howard,
Eskola, Boegh, Welden/Muir (ordered the Ponsaing book Keith
recommended, have had the others quite a while), and the more I do it
and read the greater my understanding is growing. For instance, silly
me--I thought Boegh had a particular image backwards in his book--it
was of a test strip of aquatint exposures ranging from 15 sec to 90
sec, but the lighter exposure was 15 sec. This flew in the face of
reason that the greater the exposure on solarplate the lighter the
print, so I just assumed he did it wrong. BUT what I have since
realized from rereading all books and looking at Jon's little dot
diagram, is that the exposure of the screen starts OUT washed out,
then gets blacker. No WONDER I had a calibrated exposure of screen to
be 1mn 15 sec and couldn't figure out why I needed longer. I was
looking only for where open bite disappeared, but I should have been
really looking for when first max black occurs. AND when doing this
with a UVBL unit, the exposures should NOT be in steps of 15 sec--too
short--but in 1 minute steps up to maybe 10 minutes!! I found this in
another little part in Boegh's book, a caption to a photo where it
talks about relative exposures of metal halide to UVBL.
Little things like this make more sense.
When Keith mentioned wetness of the paper a culprit, I again found ref
to the fact that blotches/uneven tones can be a result of the
wetness/dryness of the paper, lack of evenness, etc., so again, no
WONDER it is good to soak a long time but to let paper sit in bags.
So every little bit helps on my way to perfection, short of ordering a
vacuum frame. Pray for a tax refund. At least all these failures will
benefit the alt process manual chapter; no better way to learn a
process than to fail at it over and over again.
Chris
PS one last thing--when doing the Boegh and others method of clipping
tones in a curve dialog box to 80%, this only works on grayscale the
way he suggests--moving the point top right down to Input
100/Output80. If in RGB mode you have to move the bottom LEFT UP to
Input 0/Output 50--dif numbers and dif directions. But you all
already know that. I am not using this method of curving, preferring
instead to build a PDN curve with no tonal clipping, but for those who
want a low tech way of adjusting the image to suit a plate, this is it.
----- Original Message ----- From: "Jon Lybrook" <jon@terabear.com>
To: <alt-photo-process-l@usask.ca>
Sent: Saturday, February 24, 2007 10:43 AM
Subject: Sources for stochastic screens
I called around and found a guy here in Boulder who seems to know
what he's talking about in terms of outputting an 1800 dpi 80%
density stochastic screen on him imagesetter. I'm meeting with him
next week to show him the screen I'm using to see if he can
accurately reproduce it. He said typically they output at much
higher rez natively, but can make it output at 1800.
I actually called a company that sells imagesetters in New Jersey
first and asked them if they could recommend any of their clients.
They just said, look under 'typesetting' in the phone book. I was
dubious, but looked and there was one entry, for this one company.
Might try it in your own town...and help keep those imagesetters in
business! In the meantime I plan to work with this guy a little to
get at least one screen made, and if he proves reliable, and can give
me the screen I've been using without issues, I'll post their contact
info later in the week.
Hooray!
Jon
|