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Re: [PPLetterpress] another possible factor in exposing plates

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  • Mark Attwood
    Marnie wrote: Would a single light source such as a metal hallide lamp ... Marnie, I used a metal halide 5kw unit for exposing plates for some time before I
    Message 1 of 11 , Jan 9, 2002
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      Marnie wrote:

      Would a single light source such as a metal hallide lamp
      > produce crisper results?

      Marnie,
      I used a metal halide 5kw unit for exposing plates for some time before I
      got the multiple bulb fluorescent unit that I now use. My exposure times
      were VERY long (about 20 min) despite the power of the unit. After some
      research I learned that the polymer plates use a slightly different
      frequency of UV light to the metal halide, and this is where the UV
      fluorescent tubes have their wavelength.

      my 2c worth,


      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: Mon, Jan 7, 2002, 5:13 pm
      >

      > Hi all-
      >
      > I'm new to the list, and I'm unsure if this question has already been
      > raised. Has anyone considered the validity of a single light source? I
      > know that the exposure must be directly perpendicular to the plate so
      > that light does not pass through the open areas of the negative at an
      > angle, thus producing slabs on the sides of the relief areas verses a
      > hard edge. Would a single light source such as a metal hallide lamp
      > produce crisper results? That's what the printmaking stuido here at the
      > University of Utah is using for polymer and screenprinting. We (at the
      > letterpress shop) continue to use a multi-bulb black light blue
      > flourescent unit. Works great for type and line work, but not so well
      > with fine halftones. As a photographer, I've been doing a lot of
      > photographic exposures with tight line screens-- a serious challenge.
      > Boy do I hear you in regards to the plates headed straight to the waste
      > bin. I'd be interested in anyone's thoughts on this issue.
      >
      > 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
      >
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      > http://groups.yahoogroups.com/group/PPLetterpress
      > [copious reference sources can be found onsite in Bookmarks (URLs),
      > Database (tables), Files (documents), and Messages (archives)]
      >
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      > PPLetterpress-owner@yahoogroups.com
      >
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    • Marnie Powers
      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
      Message 2 of 11 , Jan 9, 2002
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        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
      • 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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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