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Re: [PPLetterpress] Re: another possible factor in exposing plate s

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  • Katie Harper
    Brian: The confusion comes between the terms dpi which refers to dots per inch --or more correctly, but rarely used, ppi pixels per inch--which refer to
    Message 1 of 7 , Jan 9, 2002
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      Brian:

      The confusion comes between the terms "dpi" which refers to "dots per inch"
      --or more correctly, but rarely used, "ppi" pixels per inch--which refer to
      input and digitizing resolution, and "lpi" meaning "lines per inch" which
      refers to output dots of a halftone screen. When a printer says that her
      press will do a 65 or 85 or 100 line halftone, she is referring to the dot
      size in the halftone, which is a series of dots that simulate grays in
      printing. Laser printers do this, too, and also ink jets, although the ink
      jets do it in such a way as to make the dots less visible. If you take any
      printed photograph and view it under a magnifying glass, you will see these
      dots. Now, in the digital world, you can, somewhat crudely, think of these
      halftone dots as being made up of pixels. So the dot, tiny as it might be,
      has even tinier components. If you render an 85-line halftone on a 300 dpi
      printer and compare it to an 85-line halftone rendered on a 1200 dpi
      printer, the 1200 dpi printer output will appear sharper, crisper and with
      better tonal rendition. If you look at both through a magnifier, you will
      see that the dots are the same size, but the 1200 dpi dot is finer and
      crisper. You probably won't notice this difference unless you view it close
      up.

      Confusing? You bet! And to make it even worse, you'd think that higher dpi
      is always better, but not! Just as a halftone screen that is too fine will
      not print well on press, so an image scanned at too high a resolution will
      cause problems in the digital world. To render the best halftone screens,
      it's best to scan an image at 1.5-2x the output lines per inch, but no
      higher than 2x. Anything over that will be not improve image quality, but
      will only make file sizes bigger. For example, if you are using a 300 dpi
      laser printer as your final output, the halftone dots will max out at about
      60 lines per inch, or lpi. 10 x 2 = 120 dots per inch or dpi, so if you scan
      at 120 dpi, your image will be as good as possible. With high resolution
      output, such as on a Linotronic or other imagesetters, the halftone dots can
      be much finer so resolution can be higher. It's best to ask your service
      bureau what settings they recommend. All this goes for images used at 100
      percent. If you enlarge the image, you must accordingly up the scanning
      resolution at scanning time because as the image is enlarged on the
      computer, the resolution drops proportionately.

      Still with us? OK. Now remember: this is for photographs. For line
      art--artwork that has no grays but only black or white--there are no
      halftones created, so you always want to scan at the highest resolution
      possible. Even "interpolated" resolution, which is a way of fudging to get
      higher resolution than is possible in reality, will sometimes improve line
      art.


      If you have any hair left, you can check out that website that Gerald
      recommended. http://halftones.info/
      It's very informative.

      Katie Harper
      Ars Brevis Press
      Cincinnati, OH
      513-233-9588

      Remember: Book arts will save the world!



      > From: Brian Molanphy <bmolanphy@...>
      > Reply-To: PPLetterpress@yahoogroups.com
      > Date: Wed, 9 Jan 2002 14:06:29 -0700
      > To: "'PPLetterpress@yahoogroups.com'" <PPLetterpress@yahoogroups.com>
      > Subject: RE: [PPLetterpress] Re: another possible factor in exposing plate s
      >
      > marnie wrote in part:
      >
      >
      >
      >> How I make the negative:
      >>
      >> Scan a 35mm slide or negative at @1200 dpi.
      >>
      >> 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...
      >>
      >>
      >>
      >>
      >>
      > marnie and list,
      >
      > first of all, please correct me if i am spreading misinformation. my
      > understanding is that letterpress polymer plates tolerate about 150 lpi or
      > 300 dpi. why no more than that, i dunno. what use is it to scan at 1200 dpi,
      > if the plate won't print more detail than 300 dpi ?
      >
      > brian
      >
      >
      > To post a message to the membership, send an email to
      > PPLetterpress@yahoogroups.com
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      > Database (tables), Files (documents), and Messages (archives)]
      >
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      >
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      >
      >
    • bielerpr
      Katie Harper wrote ... Dear Katie Just a bit to add to this. Most of my work is fixing up badly printed or badly preserved images from the past, type
      Message 2 of 7 , Jan 9, 2002
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        Katie Harper wrote

        > Still with us? OK. Now remember: this is for photographs. For line
        > art--artwork that has no grays but only black or white--there are no
        > halftones created, so you always want to scan at the highest resolution
        > possible. Even "interpolated" resolution, which is a way of fudging to get
        > higher resolution than is possible in reality, will sometimes improve line
        > art.

        Dear Katie

        Just a bit to add to this. Most of my work is fixing up badly printed
        or badly preserved images from the past, type specimens, copper or
        steel or wood engravings, illuminated manuscript work, etc. When I am
        scanning for line art reproduction, I always scan in grayscale at the
        highest resolution I can. While a pain in the butt to work with, re
        memory capacity limitations, this gives me a lot more flexibility in
        refinement. You can pop this up once (there is a term for this?) at
        2x but that is about the effective limit, and this should be done
        before you start working with the image. Final output for b/w line
        art (as opposed to halftone) must be at 1200 dpi (minimum) to prevent
        bitmapping (for generating a film negative from a Linotronic).

        Nice response by the way

        Gerald
      • Brian Molanphy
        katie wrote, in part: If you render an 85-line halftone on a 300 dpi ... i get this, basically. but if polymer plates have a limit of about 150 lpi or 300
        Message 3 of 7 , Jan 9, 2002
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          katie wrote, in part:

          'If you render an 85-line halftone on a 300 dpi
          > printer and compare it to an 85-line halftone rendered on a 1200 dpi
          > printer, the 1200 dpi printer output will appear sharper, crisper and with
          > better tonal rendition. If you look at both through a magnifier, you will
          > see that the dots are the same size, but the 1200 dpi dot is finer and
          > crisper.'
          >
          i get this, basically. but if polymer plates have a 'limit' of about
          150 lpi or 300 dpi, what use is the 1200 dpi file ? the file, or the
          laserprint, may have more detail, but will that detail show up on a polymer
          plate? this question may be more meaniful if, for example, one is committing
          the heresy that i do, which is to generate negatives on my 600 dpi laser
          printer.

          brian
        • Katie Harper
          Brian: I guess I don t quite get what you are saying about the limit of about 150 lpi or 300 dpi ... is this something you have read somewhere, some kind of
          Message 4 of 7 , Jan 9, 2002
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            Brian: I guess I don't quite get what you are saying about the "limit of
            about 150 lpi or 300 dpi"... is this something you have read somewhere, some
            kind of specification? I'm sure that photopolymer probably does have a limit
            as to how small a speck it can hold (ie, how fine a halftone dot), but I'm
            pretty sure it is capable of holding much finer detail than most
            letterpresses can print, so the limitation you speak of is not from the
            plate but from the press. In any case, I cannot see how a polymer plate can
            be limited by 300 dpi, since the plate is analog and the term "dpi" refers
            to the digital world.

            And yes, the difference between output from a 600 dpi output device and a
            1200 dpi or larger resolution output device will show, but whether or not
            that difference matters depends on a)what you are printing, b)what you are
            printing on, c) what press you are using and d) what ink. There are probably
            other factors including temperature, roller condition, what the printer has
            for breakfast, and on and on... But it mainly depends on what is acceptable
            quality for the printer or the client. What works for a daily newspaper
            won't be considered acceptable for a slick magazine or a coffee table book
            printed in Italy. One plate may look like royal doo-doo on one type of paper
            and swell on another. For my own work, I tend to try to get the best
            possible image from a plate, so that all the other factors which will
            whittle down the quality have to start from a higher place. Having said
            that, I will add there are times when a home-made neg will work and times
            when it won't. Just as there are times when taking an exposed piece of film
            and scratching a drawing on it will make a great negative, and times when I
            need a careful rendering of an original or a computer file. I'm talking
            images here. With type, I take no chances and get the best quality output
            and plates I can.

            Katie Harper
            Ars Brevis Press
            Cincinnati, OH
            513-233-9588

            Remember: Book arts will save the world!



            > From: Brian Molanphy <bmolanphy@...>
            > Reply-To: PPLetterpress@yahoogroups.com
            > Date: Wed, 9 Jan 2002 20:12:22 -0700
            > To: "'PPLetterpress@yahoogroups.com'" <PPLetterpress@yahoogroups.com>
            > Subject: RE: [PPLetterpress] Re: another possible factor in exposing plate s
            >
            > katie wrote, in part:
            >
            > 'If you render an 85-line halftone on a 300 dpi
            >> printer and compare it to an 85-line halftone rendered on a 1200 dpi
            >> printer, the 1200 dpi printer output will appear sharper, crisper and with
            >> better tonal rendition. If you look at both through a magnifier, you will
            >> see that the dots are the same size, but the 1200 dpi dot is finer and
            >> crisper.'
            >>
            > i get this, basically. but if polymer plates have a 'limit' of about
            > 150 lpi or 300 dpi, what use is the 1200 dpi file ? the file, or the
            > laserprint, may have more detail, but will that detail show up on a polymer
            > plate? this question may be more meaniful if, for example, one is committing
            > the heresy that i do, which is to generate negatives on my 600 dpi laser
            > printer.
            >
            > brian
            >
            >
            > 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/
            >
            >
          • Brian Molanphy
            katie, i get this from info sheet from our plate supplier, gene becker: our plates... will hold a 3% dot on a 150 line screen. brian
            Message 5 of 7 , Jan 9, 2002
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              katie,

              i get this from info sheet from our plate supplier, gene becker: 'our
              plates... will hold a 3% dot on a 150 line screen.'

              brian

              > ----------
              > From: Katie Harper
              > Reply To: PPLetterpress@yahoogroups.com
              > Sent: Wednesday, January 9, 2002 8:40 PM
              > To: PPLetterpress@yahoogroups.com
              > Subject: Re: [PPLetterpress] Re: another possible factor in exposing
              > plate s
              >
              > Brian: I guess I don't quite get what you are saying about the "limit of
              > about 150 lpi or 300 dpi"... is this something you have read somewhere,
              > some
              > kind of specification? I'm sure that photopolymer probably does have a
              > limit
              > as to how small a speck it can hold (ie, how fine a halftone dot), but I'm
              > pretty sure it is capable of holding much finer detail than most
              > letterpresses can print, so the limitation you speak of is not from the
              > plate but from the press. In any case, I cannot see how a polymer plate
              > can
              > be limited by 300 dpi, since the plate is analog and the term "dpi" refers
              > to the digital world.
              >
              > And yes, the difference between output from a 600 dpi output device and a
              > 1200 dpi or larger resolution output device will show, but whether or not
              > that difference matters depends on a)what you are printing, b)what you are
              > printing on, c) what press you are using and d) what ink. There are
              > probably
              > other factors including temperature, roller condition, what the printer
              > has
              > for breakfast, and on and on... But it mainly depends on what is
              > acceptable
              > quality for the printer or the client. What works for a daily newspaper
              > won't be considered acceptable for a slick magazine or a coffee table book
              > printed in Italy. One plate may look like royal doo-doo on one type of
              > paper
              > and swell on another. For my own work, I tend to try to get the best
              > possible image from a plate, so that all the other factors which will
              > whittle down the quality have to start from a higher place. Having said
              > that, I will add there are times when a home-made neg will work and times
              > when it won't. Just as there are times when taking an exposed piece of
              > film
              > and scratching a drawing on it will make a great negative, and times when
              > I
              > need a careful rendering of an original or a computer file. I'm talking
              > images here. With type, I take no chances and get the best quality output
              > and plates I can.
              >
              > Katie Harper
              > Ars Brevis Press
              > Cincinnati, OH
              > 513-233-9588
              >
              > Remember: Book arts will save the world!
              >
              >
              >
              > > From: Brian Molanphy <bmolanphy@...>
              > > Reply-To: PPLetterpress@yahoogroups.com
              > > Date: Wed, 9 Jan 2002 20:12:22 -0700
              > > To: "'PPLetterpress@yahoogroups.com'" <PPLetterpress@yahoogroups.com>
              > > Subject: RE: [PPLetterpress] Re: another possible factor in exposing
              > plate s
              > >
              > > katie wrote, in part:
              > >
              > > 'If you render an 85-line halftone on a 300 dpi
              > >> printer and compare it to an 85-line halftone rendered on a 1200 dpi
              > >> printer, the 1200 dpi printer output will appear sharper, crisper and
              > with
              > >> better tonal rendition. If you look at both through a magnifier, you
              > will
              > >> see that the dots are the same size, but the 1200 dpi dot is finer and
              > >> crisper.'
              > >>
              > > i get this, basically. but if polymer plates have a 'limit' of about
              > > 150 lpi or 300 dpi, what use is the 1200 dpi file ? the file, or the
              > > laserprint, may have more detail, but will that detail show up on a
              > polymer
              > > plate? this question may be more meaniful if, for example, one is
              > committing
              > > the heresy that i do, which is to generate negatives on my 600 dpi laser
              > > printer.
              > >
              > > brian
              > >
              > >
              > > 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/
              > >
              > >
              >
              >
              >
              > 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/
              >
              >
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