Hey Chris,
thanks for taking time to post this info! Very interesting stuff. I
look forward to someone jumping in here to translate... one of the
many nice things about this list :o)
susan
On 4/8/07, Jon Lybrook <jon@terabear.com> wrote:
> \Christina Z. Anderson wrote:
> > 2. Exposing is done in 3 stages--main exposure first for **15**
> > minutes with the light source at 1/2 the distance of the aquatint
> > exposure. Aquatint exposure SECOND--**15** minutes with the distance
> > of the light 1 1/2 the diagonal of the vacuum frame measure. Post
> > exposure 5 minutes. (on a Stouffers dark steps 8, 9, and 10 should be
> > "clearly defined").
> Maybe he's using a maglight to make his exposures. ;-)
>
> > With the inverse square law of light 1/2 the distance of the positive
> > means it is 4x the length of exposure, correct? So Ponsaing's ratio
> > of exposure is 4pos/1aquatint. Can you believe the length of his
> > times??!! I can't read the text to see what his light source is,
> > though, unfortunately. I can glean that he is using Japanese plates KM73.
> >
> > Oh, here are his light choices: "uv lys, kviksolvdamplampe hpr 125,
> > drosselspole bhl 125 eller l44, metalhalogenhampe, xenon lampe. And
> > then Ikke alle lyskilder er egnede til vor kopiering. Der kraeves
> > lysbolgelaengder mellem 400-360 my i det ultraviolet-te omrade af
> > spektret. Ved anvendelse af FP-plader til dybtryk, er punktlys bedst
> > egnet, d.v.s. at lyskilden har sa lille en udstraekning som muligt.
> > Dette lys findes i kviksolvdamplampe, hojfjeldssol, xenonlampe,
> > metalhalogenlampe og kulbuelampe.
> >
> > My interest in the light source choice is to compare his longer
> > exposures with what we are doing with KM73s. What he is doing is
> > still not disproving my theory that the length of exposure is not as
> > crucial as the ratio, unless, say, he is using REALLY weak bulbs which
> > I don't think is true--I can at least decipher halogen in there. But
> > it still supports the theory that, like gum, the longer exposure (to a
> > point) the thicker the layer of goo on top of the substrate, whence
> > comes Welden's description of the forgiving latitude of exposure of
> > the plates, that exposure is not so crucial.
> So based on your theory Chris, if my ratio is 1:1 screen/image, I could
> do 10 seconds/ 10 seconds, or 1min/1min, or 15min/15min and it wouldn't
> make a huge difference? This might be true to some degree if one is
> using imagesetter film for both, since the density of imagesetter film
> is so heavy. I'd expect the dots would change size as time is
> increased though, since the longer exposures would allow more light to
> sneak underneath the edges of the dots. Easy enough to test
>
> Thanks for the posting!
>
> Jon
>
>
--
susan
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