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Re: Photopolymer Optimization of letterforms

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  • dpwall@hotmail.com
    Gerald: ... The -.064 choke is neither normative nor maximum. It just happens to be what gave the best overall effect for that particular test page. For best
    Message 1 of 7 , Aug 29, 2001

      I'm glad you like the proofs. In response to your questions:

      > Is the -.064 choke normative or maximum?
      The -.064 choke is neither normative nor maximum. It just happens to
      be what gave the best overall effect for that particular test page.
      For best results I think you should apply less choke to smaller sizes
      of type, and more to the larger, and it bears some experimentation
      with the amounts applied to different typefaces. I found that
      the "gain" from my laser printer (relative to the high resolution of
      an imagesetter) roughly mimics the gain from letterpress, and it is
      therefore possible to experiment first with laser proofs before
      wasting a lot of expensive film and plate material.

      > How much further could you choke before you experience letterform
      > breakup?
      The amount of additional choke that can be applied depends both on
      the specific typeface design, and on the size at which you are
      reproducing it. Smaller types, and those with finer lines, will start
      to break up before the larger sizes and heavier designs. Quark allows
      a choke of up to -36 points---three whole picas!---which is obviously
      far more latitude than we need for this purpose. In most cases I
      would think an appropriate amount of choke for a text face would be
      between -0.100 and -.008 points, depending on the size and the design.

      > I assume this is possible in PageMaker, Illustrator, InDesign as
      > well, do you know?
      I do not have first-hand experience in trapping/choking with these
      programs, but they undoubtedly must all have some sort of function
      for addressing trapping of colors to one another. If so, they can
      probably be adapted to choke the text the same way that it works in

      > Does this effect leading or other page parameters; line length,
      > text block measure, etc?
      The choking/trapping does not have any significant effect on line
      length or text block size. It basically is just the reverse of the
      gain that you get from ink squeeze on press.

      > What are the difficulties encountered in explaining the trapping to
      > the folks at the service bureau (film house)?
      The problem that I encountered with one film house was just in trying
      to make it clear to them what I wanted the final output to look like.
      It can be confusing because what you need is positive film of the
      colored background (this is what has the choked type knocked out of
      it), which will end up looking kind of like a negative piece of film.
      And of course, the film also needs to be right-reading/emulsion-up.
      For most service bureaus it should not be a problem if you ask them
      for RREU Positive film of the color channel. If they are outputting a
      file that you prepared yourself, they should not need to do anything
      with regard to the trapping/choking. (Note that you do not want film
      for the black channel, even though this is technically the channel
      with the type in it.)

      I hope this is making some sense to everyone. It is much easier for
      me to explain in person, where I can draw diagrams and use hand
      gestures. I will gladly try to answer more questions if you have them.

      With best regards,

      David Wall
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