Re: Sources for stochastic screens

[SusanV <susanvoss3@gmail.com>]

Jon and Chris..

Great work on all this screen information.  Another reason this list
and the people on it are such treasures!

As for the curves discussions, I must admit that when I start reading
about those things, my hair hurts.  I'm just not up to speed when it
comes to curves (as relating to digital positive/negatives for alt
process output).  I don't even understand a lot of the terms you all
use ( "100% mapped to about 82%", "moving the point top right down to
Input
100/Output80" ....SAY WHAT?????  ).  I'm just late to this digital
neg/pos party you've all been doing for a while now.  I'm not at all a
technophobe... but in this particular instance, I just want a simple
solution to get me making my images.  I'm using Jon's curves at this
point, but I do wish I understood how to tweak them to get the best
result for my own workflow with the 1280 printer and Nuarc and km73
plates, etc...

ok, i'll stop whining, haha... it's just been a killer week here and
I'm wiped out.  I'll go take a nap and come back later :o)

susan

www.susanvossgravures.blogspot.com
www.dalyvoss.com


On 2/24/07, Jon Lybrook <jon@terabear.com> wrote:
> 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
> >>
> >>
> >>
> >
> >
> >
--
susan
gravure blog at www.susanvossgravures.blogspot.com
website www.dalyvoss.com