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Digital configuration: was Blurry Plates

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  • Gerald Lange
    Dear Dan Couple of considerations for this. I ve not specifically encountered this before but based on technical information mixed with a bit of theory I ll
    Message 1 of 1 , Sep 27, 2001
      Dear Dan

      Couple of considerations for this. I've not specifically encountered
      this before but based on technical information mixed with a bit of
      theory I'll take a stab at it, though I'd be quite interested in
      comments from others. Let me know if this seems to fit what you are
      doing or if I am completely off base here.

      First, in terms of the printing surface. What you see (on the
      negative) is what you get (or, more to the point, what you need to
      strive for). Halation (cross-filtering as the molecular structure
      reforms and cross-links) is a filling-in process that increases with
      exposure. This primarily effects the shoulder. Thus the relief depth
      actually decreases with more exposure. Halation provides stability to
      the shoulder during washout which will then need post-exposing to
      completely strengthen it for printing. It does not affect the printing
      surface per se.

      You would normally want less exposure on a broad surface because you
      would have more of an ink drain. The UV does not get bounced around as
      you suspect. The effect is on the exposed image. The "new" technology
      "sheet polymer" is already back-exposed so there is no reflection back
      up from the metal-backing. "Older" technology required back-exposing.
      The reason you can't actually wash away that thin layer of polymer at
      the plate's "floor" is because it was pre-photopolymerized at the
      manufacturer. This is technically known as the anti-halation layer. So
      I don't think its the plates here, though exposure times do have a
      significant effect on image. A thinning effect with increased exposure
      and vice versa.

      I believe this to be a pre-processing problem/solution. Essentially it
      has to do with ink gain. If you are working with linocuts I assume the
      image is coming from a printed reproduction. Already you have a
      certain amount of ink gain. If you are furnishing this proof to be
      then made into a negative you are also then dealing with camera
      distortion and an added set of exposure considerations.

      The solution here, I think, is to digitally scan the proofs and rework
      them in an image-editing program like Photoshop. We had talked here
      earlier about the letterpress configuration of digital type. I believe
      this to be crucial for best results. The same applies to images. A
      good percentage of the commission work that comes in to my shop is
      just that. Digitally reconstructing images for photopolymer printing.

      Here, you need to open up the white areas a bit. You do not have to
      alter them just increase their relative size in proportion to the
      black. Not a lot of increase is required. You could, for example,
      click on an internal white area of your image, select all similar
      areas, and then increase the relative size of the white (apply pixel
      growth). Note that you need to do this from a grayscale scan (at
      600dpi, or, if you can, at 1200dpi) not a black/white scan (as you
      cannot change the black/white w/o actually altering the image). When
      you are finished with your alterations, increase the dpi to 1200 then
      convert the image to black/white. All you are really trying to do is
      visually compensate for gain, not alter the image.

      Maybe you know all this, but a lot of folks think that images don't
      need to be adjusted. The reason we now use photopolymer for
      letterpress is because it has been tied into digital imaging. The
      process has been around for some forty odd years but never caught on
      for fine printing previously because it was dependent on printed
      reproduction with no way to independently control output. Now we have
      that. Aren't we lucky :-).

      Gerald
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