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RE: [PPLetterpress] Halftones and photopolymer

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  • Ed Inman
    I assume you are making B&W halftones rather than CMYK. You want to first edit the photo in a program like Adobe Photoshop. It sometimes helps to maintain
    Message 1 of 7 , Dec 17, 2005
      I assume you are making B&W halftones rather than CMYK.

      You want to first edit the photo in a program like Adobe Photoshop. It
      sometimes helps to maintain highlight detail by slightly darkening bright
      colors like white and yellow. From there, adjust the brightness for
      optimal results on the main subject. Then, gradually reduce contrast until
      their is a uniform minimum dot pattern of approximately 20 percent
      throughout all highlight areas.

      There may be a more sophisticated way, but the above process generally
      works pretty good for me.

      Ed

      > [Original Message]
      > From: Gerald Lange <bieler@...>
      > I've not had problems with halftones that I have configured but I am
      > getting a lot of stuff from folks where the lower end of the grayscale
      > drops out, leaving holes in the image surface. I assume this has more
      > to to do with too much contrast in the photo and possibly a
      > combination that also has to do with the line screen specified.
    • Gerald Lange
      Ed Actually, I m just processing plates, I rarely use halftones for letterpress work. I m mainly hoping for some useful information to teach folks who want
      Message 2 of 7 , Dec 17, 2005
        Ed

        Actually, I'm just processing plates, I rarely use halftones for
        letterpress work. I'm mainly hoping for some useful information to
        teach folks who want halftones how to configure them properly. I've
        gotten some very good responses offline but that doesn't exactly help
        folks here.

        Can't imagine a four color halftone with photopolymer; sounds like a
        registration nightmare, but I would agree with your instruction,
        though to do it properly a lot of old school technique is required.
        And while many folks know how to make wonderful photographs many do
        not know how to configure them for print reproduction.

        Gerald

        I've gotten a number of responses offlist--- In
        PPLetterpress@yahoogroups.com, "Ed Inman" <edinman@e...> wrote:
        >
        >
        > I assume you are making B&W halftones rather than CMYK.
        >
        > You want to first edit the photo in a program like Adobe Photoshop. It
        > sometimes helps to maintain highlight detail by slightly darkening
        bright
        > colors like white and yellow. From there, adjust the brightness for
        > optimal results on the main subject. Then, gradually reduce contrast
        until
        > their is a uniform minimum dot pattern of approximately 20 percent
        > throughout all highlight areas.
        >
        > There may be a more sophisticated way, but the above process generally
        > works pretty good for me.
        >
        > Ed
      • raceroberts
        ... While working at Rohner Letterrpess in Chicago a few years ago, we printed a 4 color halftone holiday card for a client using photopolymer. We talked about
        Message 3 of 7 , Dec 18, 2005
          --- In PPLetterpress@yahoogroups.com, "Gerald Lange" <bieler@w...> wrote:
          > Can't imagine a four color halftone with photopolymer; sounds like a
          > registration nightmare, but I would agree with your instruction,
          > though to do it properly a lot of old school technique is required.
          > And while many folks know how to make wonderful photographs many do
          > not know how to configure them for print reproduction.

          While working at Rohner Letterrpess in Chicago a few years ago, we printed a 4 color halftone
          holiday card for a client using photopolymer. We talked about getting the image litho'ed and
          then debossing the image, but the client wanted it letterpressed, and truth be told, Rohner
          loved/loves a challenge.

          Using windmills solved any challenge of registration, though determining the ink coverage
          took total old school know-how. My boss' father, Rudy Rohner (retired), pretty much ran the
          whole job while the rest of us young'uns watched in awe.

          I honestly don't recall any corrections we had to make to the image DPI configuration before
          burning a plate, so I can't offer any advice there. Sorry!
        • Ed Inman
          I ve experimented with 4-color CMYK on my C&P handfed with pretty good success, though the image came out a little contrasty compared to offset (with sort of
          Message 4 of 7 , Dec 18, 2005
            I've experimented with 4-color CMYK on my C&P handfed with pretty good success, though the image came out a little contrasty compared to offset (with sort of an old fashioned comic book look to it).
            I made the color seps in Adobe Photoshop and exposed four separate photopolymer plates.

            Registration on a C&P is not really difficult--I just tape down a piece of clear mylar and pull the first impression onto it. Then I carefully position the card in the proper place to line up under the mylar image, draw a line around the edges of the card onto the tympan paper, then place the pins accordingly.

            If you feed carefully the press will hold amazingly good registration, although there will always be a few that you will end up having to discard that get out of hairline register. Of course the more colors you run the higher the number of discards, but even with 4-color work you should be able to keep an average of about 70 to 80 percent in good register.

            Having to repeatedly wash up and re-ink the press is the hardest part, IMO. You really need the rollers to be spotlessly clean to do any sort of process color.

            Ed

            -----Original Message-----
            >From: raceroberts <raceroberts@...>
            >While working at Rohner Letterrpess in Chicago a few years ago, we printed a 4 color halftone
            >holiday card for a client using photopolymer. We talked about getting the image litho'ed and
            >then debossing the image, but the client wanted it letterpressed, and truth be told, Rohner
            >loved/loves a challenge.
          • John G. Henry
            When setting up halftone images in Photoshop, I generally do flatten the image a bit (reducing the contrast) as you tend to gain contrast through the halftone
            Message 5 of 7 , Dec 19, 2005
              When setting up halftone images in Photoshop, I generally do flatten
              the image a bit (reducing the contrast) as you tend to gain contrast
              through the halftone process. In whatever program you are using, you
              need to make certain that you have at least a good 10% dot in the
              highlight, and a 90% dot in the shadow. If you start to lose either
              end, the image starts to become very muddy and or spotty in appearance.

              I was always taught that dropouts (no dot at all) were OK
              in "specular" highlights. That is areas in which you would expect no
              density at all such as bright reflections. It seems to me that dropped
              dots become very obvious when dealing with line screens under 133
              lines/in., and dropouts should be avoided if possible.

              In my opinion, a 20% dot would be too heavy for something which has
              detail in the highlights you wish to keep, but experience with various
              papers and images is the best teacher. Most recently I have been
              printing halftone images for miniature books, where the images are
              small and detail is important. At 133-line screen, with coated paper,
              it is surprising what detail can be resolved. Even after considerable
              experience with the process, I am still frustrated on occasion with
              the results. More often than not, however, control of the process
              leads to better images.

              John G. Henry
              Cedar Creek Press
            • Gerald Lange
              John This seems fairly lucid. Thanks. Some other technical manipulations such as dodging and burning appropriate areas would result in better reproduction but
              Message 6 of 7 , Dec 20, 2005
                John

                This seems fairly lucid. Thanks. Some other technical manipulations
                such as dodging and burning appropriate areas would result in better
                reproduction but I doubt most folks are all that skilled in these
                matters. I don't know that the planar imagery is all that appropriate
                for letterpress anyway but that doesn't stop folks from trying.

                I'm currently looking at the restoration of an old copper plate
                engraving for a fellow. Far more engaging and much more my cup of tea.

                Gerald

                --- In PPLetterpress@yahoogroups.com, "John G. Henry" <JohnH@i...> wrote:
                >
                > When setting up halftone images in Photoshop, I generally do flatten
                > the image a bit (reducing the contrast) as you tend to gain contrast
                > through the halftone process. In whatever program you are using, you
                > need to make certain that you have at least a good 10% dot in the
                > highlight, and a 90% dot in the shadow. If you start to lose either
                > end, the image starts to become very muddy and or spotty in appearance.
                >
                > I was always taught that dropouts (no dot at all) were OK
                > in "specular" highlights. That is areas in which you would expect no
                > density at all such as bright reflections. It seems to me that dropped
                > dots become very obvious when dealing with line screens under 133
                > lines/in., and dropouts should be avoided if possible.
                >
                > In my opinion, a 20% dot would be too heavy for something which has
                > detail in the highlights you wish to keep, but experience with various
                > papers and images is the best teacher. Most recently I have been
                > printing halftone images for miniature books, where the images are
                > small and detail is important. At 133-line screen, with coated paper,
                > it is surprising what detail can be resolved. Even after considerable
                > experience with the process, I am still frustrated on occasion with
                > the results. More often than not, however, control of the process
                > leads to better images.
                >
                > John G. Henry
                > Cedar Creek Press
                >
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