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Re: another possible factor in exposing plates

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  • Marnie Powers
    Gerald- The information that you provided was very interesting. I m somewhat familiar with the collotype process and know photosilkcreen fairly well. I realize
    Message 1 of 11 , Jan 9, 2002
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      Gerald-

      The information that you provided was very interesting. I'm somewhat
      familiar with the collotype process and know photosilkcreen fairly
      well. I realize these are birds of a different feather.

      To respond to your query about our exposure unit: it's a handmade job
      with a powerful vacuum accompanied by the translucent vacuum film
      that Gene Becker sells. The light source is six black light blue
      flourescent bulbs. There's about an inch between the surface to be
      exposed and the bulbs. Works very well except for high resolution
      photographs. Or rather, I do very well except with high resolution
      photographs.

      How I make the negative:

      Scan a 35mm slide or negative at @1200 dpi. Especially if it's low
      contrast, I play around with the curves in photoshop, condensing? the
      values somewhat (move the two points at either end of the diagonal
      inward so that I have a "new" diagonal line that runs directly parallel
      to and above the "original" one). It seems that I loose less detail this
      way then when I change the contrast/brightness, while still acheiving
      a denser negative with a little less tonal range. I have the image output
      on imagesetting film with a stochastic screen at "80". The difficutly is
      that the stochastic screen (as I understand it anyway) does not directly
      translate to lpi. With lower resolution photos the results are excellent.
      Using a negative produced in the darkroom with a tradition halftone
      screen, the results are excellent. I'm just trying to push the process a
      bit further.

      Maybe the dot gain is just too great on the letterpess. Or maybe when
      the dots get too small, the relief in the plate is not substantial enough.
      I've been able to do very high resolution/low contrast/high detail
      work with photopolymer plates printed intaglio, that I keep wanting
      the same to be possible with letterpress.

      I'd very much appreciate your (or anyone else's) feedback on how I'm
      dealing with these chanllenges...

      Best,

      Marnie
      Marnie Powers-Torrey
      Studio Manager
      Book Arts Program
      J.Willard Marriott Library
      (801)585-9191
    • bielerpr
      Dear Marnie Here s a useful page with a lot of links re: the halftone process http://halftones.info/ For further ref this is in Bookmarks under Tech Info
      Message 2 of 11 , Jan 9, 2002
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        Dear Marnie

        Here's a useful page with a lot of links re: the halftone process

        http://halftones.info/

        For further ref this is in Bookmarks under Tech Info

        Gerald
      • Katie Harper
        ... I m unfamiliar with the term stochastic screen. Can you explain what this is? Thanks. Katie Harper
        Message 3 of 11 , Jan 9, 2002
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          > From: "Marnie Powers" <mpowers@...>
          > Organization: Marriott Library
          > Reply-To: PPLetterpress@yahoogroups.com
          > Date: Wed, 9 Jan 2002 11:29:26 -0700
          > To: PPLetterpress@yahoogroups.com
          > Cc: vhindley@...
          > Subject: [PPLetterpress] Re: another possible factor in exposing plates
          >
          > I have the image output
          > on imagesetting film with a stochastic screen at "80". The difficutly is
          > that the stochastic screen (as I understand it anyway) does not directly
          > translate to lpi.


          I'm unfamiliar with the term "stochastic" screen. Can you explain what this
          is? Thanks.

          Katie Harper
        • Marnie Powers
          Hi Katie- I m willing to explain the stochastic screen to the best of my ability. As I understand it, it is not a random screen. Under a loupe it looks very
          Message 4 of 11 , Jan 9, 2002
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            Hi Katie-

            I'm willing to explain the stochastic screen to the best of my ability.
            As I understand it, it is not a random screen. Under a loupe it looks
            very similar to the grain of photographic film and paper. The screen
            applies a spattered pattern to the image, the dots occurring more
            frequently in dark areas than in the light areas. In terms of fooling the
            eye into thinking it's seeing grayscale, stochastic is the most effective
            screen currently availabe. Software is expensive, and I have my
            service bureau do it. It's not used for offset prepress work however, so
            finding a provider can be a little challenging.

            Best,

            Marnie

            To: <PPLetterpress@yahoogroups.com>
            From: Katie Harper <knharper@...>
            Date sent: Wed, 09 Jan 2002 14:54:12 -0500
            Subject: Re: [PPLetterpress] Re: another possible factor in exposing plates
            Send reply to: PPLetterpress@yahoogroups.com

            [ Double-click this line for list subscription options ]






            > From: "Marnie Powers" <mpowers@...>
            > Organization: Marriott Library
            > Reply-To: PPLetterpress@yahoogroups.com
            > Date: Wed, 9 Jan 2002 11:29:26 -0700
            > To: PPLetterpress@yahoogroups.com
            > Cc: vhindley@...
            > Subject: [PPLetterpress] Re: another possible factor in exposing plates
            >
            > I have the image output
            > on imagesetting film with a stochastic screen at "80". The difficutly is
            > that the stochastic screen (as I understand it anyway) does not directly
            > translate to lpi.


            I'm unfamiliar with the term "stochastic" screen. Can you explain what this
            is? Thanks.

            Katie Harper




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            Marnie Powers-Torrey
            Studio Manager
            Book Arts Program
            J.Willard Marriott Library
            (801)585-9191
          • bielerpr
            ... Dear Marnie Have you tried ISIS Icefields (grayscale software, renders stochastic, available as a plug-in for Photoshop)? Heard great things, especially
            Message 5 of 11 , Jan 9, 2002
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              Marnie Powers wrote:

              > I'm willing to explain the stochastic screen to the best of my ability.
              > As I understand it, it is not a random screen. Under a loupe it looks
              > very similar to the grain of photographic film and paper. The screen
              > applies a spattered pattern to the image, the dots occurring more
              > frequently in dark areas than in the light areas. In terms of fooling the
              > eye into thinking it's seeing grayscale, stochastic is the most effective
              > screen currently availabe. Software is expensive, and I have my
              > service bureau do it. It's not used for offset prepress work however, so
              > finding a provider can be a little challenging.

              Dear Marnie

              Have you tried ISIS Icefields (grayscale software, renders
              stochastic, available as a plug-in for Photoshop)? Heard great
              things, especially for inkjet.

              http://www.isisimaging.com


              Gerald
            • Mark Attwood
              Marnie, It was a few years ago that I did the research into the different wavelengths, and it seems I haven t filed it. The suppliers of the plates will be
              Message 6 of 11 , Jan 10, 2002
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                Marnie,

                It was a few years ago that I did the research into the different
                wavelengths, and it seems I haven't filed it. The suppliers of the plates
                will be able to tell you the best wavelength to expose their plates, and the
                suppliers of the bulbs will give you detailed info on the output wavelength
                of the lamp. If I remember correctly there was only a small overlap at one
                end of the spectrum, and this is why the metal halide will work, but only
                with such a long exposure.

                let me know what you find out,

                Regards,
                Mark.


                Mark Attwood

                The Artists' Press
                Box 623
                Newtown
                2113
                South Africa

                Tel. +27 11 836 5474
                fax. +27 11 836 6858
                mark@...


                ----------
                >From: "Marnie Powers" <mpowers@...>
                >To: PPLetterpress@yahoogroups.com
                >Subject: [PPLetterpress] another possible factor in exposing plates
                >Date: Wed, Jan 9, 2002, 5:56 pm
                >

                > Mark,
                >
                > Thanks much for the information. Do you have any details on the
                > specific UV frequency of metal halide verses flourescent, and the ideal
                > frequency for exposing photopolymer plates? If so, I'd be interested in
                > seeing it.
                >
                > Best,
                >
                > Marnie
                > Marnie Powers-Torrey
                > Studio Manager
                > Book Arts Program
                > J.Willard Marriott Library
                > (801)585-9191
                >
                >
                > To post a message to the membership, send an email to
                > PPLetterpress@yahoogroups.com
                >
                > To log on to the groupsite (confirmed Yahoo ID required), go to
                > http://groups.yahoogroups.com/group/PPLetterpress
                > [copious reference sources can be found onsite in Bookmarks (URLs),
                > Database (tables), Files (documents), and Messages (archives)]
                >
                > Encountering problems? send an email to
                > PPLetterpress-owner@yahoogroups.com
                >
                > To unsubscribe, send an email to
                > PPLetterpress-unsubscribe@yahoogroups.com
                >
                >
                >
                > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                >
              • Marnie Powers
                Gerald I m so glad that I joined this list. I ve learned so much already! Your referrals have been extraordinarilly helpful, and the discussion is to the point
                Message 7 of 11 , Jan 11, 2002
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                  Gerald

                  I'm so glad that I joined this list. I've learned so much already! Your
                  referrals have been extraordinarilly helpful, and the discussion is to
                  the point and interesting.

                  Best,
                  Marnie

                  To: PPLetterpress@yahoogroups.com
                  From: "bielerpr" <bieler@...>
                  Date sent: Wed, 09 Jan 2002 23:22:58 -0000
                  Subject: [PPLetterpress] Re: another possible factor in exposing plates
                  Send reply to: PPLetterpress@yahoogroups.com

                  [ Double-click this line for list subscription options ]

                  Marnie Powers wrote:

                  > I'm willing to explain the stochastic screen to the best of my ability.
                  > As I understand it, it is not a random screen. Under a loupe it looks
                  > very similar to the grain of photographic film and paper. The screen
                  > applies a spattered pattern to the image, the dots occurring more
                  > frequently in dark areas than in the light areas. In terms of fooling the
                  > eye into thinking it's seeing grayscale, stochastic is the most effective
                  > screen currently availabe. Software is expensive, and I have my
                  > service bureau do it. It's not used for offset prepress work however, so
                  > finding a provider can be a little challenging.

                  Dear Marnie

                  Have you tried ISIS Icefields (grayscale software, renders
                  stochastic, available as a plug-in for Photoshop)? Heard great
                  things, especially for inkjet.

                  http://www.isisimaging.com


                  Gerald





                  To post a message to the membership, send an email to
                  PPLetterpress@yahoogroups.com

                  To log on to the groupsite (confirmed Yahoo ID required), go to
                  http://groups.yahoogroups.com/group/PPLetterpress
                  [copious reference sources can be found onsite in Bookmarks (URLs),
                  Database (tables), Files (documents), and Messages (archives)]

                  Encountering problems? send an email to
                  PPLetterpress-owner@yahoogroups.com

                  To unsubscribe, send an email to
                  PPLetterpress-unsubscribe@yahoogroups.com



                  Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


                  Marnie Powers-Torrey
                  Studio Manager
                  Book Arts Program
                  J.Willard Marriott Library
                  (801)585-9191
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