Adobe InDesign CS3 - Manual (Page 477)

INDESIGN CS3
User Guide
470
Printing books with conflicting trap presets
You can apply one trap preset to one sheet of output, such as one page. Normally this is not a concern. However, if
you print multiple documents in a book, and each document or page has a different trap preset, InDesign can resolve
some trap preset conflicts by synchronizing presets among documents:
• If documents in a book use different trap presets with the same name, InDesign assigns the trap preset used in the
master document, provided you’ve selected the Trap Preset option in the Synchronize Options dialog box.
• The synchronizing feature makes all the master document’s presets available to the other documents in the book,
but does not assign them; you have to assign trap presets in each document, or use the [Default] trap preset. The
presets appear in the Trap Preset menu of the document’s Assign Trap Presets dialog box.
Note: If different trap presets are applied to pages in a spread, InDesign honors each trap preset.
See also
“Synchronize book documents” on page 275
Adjusting ink options for trapping
Adjusting ink neutral density values
By adjusting the ink neutral density (ND) values that the selected trapping engine uses, you can determine the
precise placement of traps. The default ND values for process inks are based on the neutral density readings of
process ink swatches that conform to industry standards in different parts of the world. The language version deter-
mines which standard it conforms to. For example, the ND values for the U.S. English and Canadian versions
conform to the Specifications for Web Offset Publications (SWOP) solid ink density values published by the Graphic
Arts Technical Foundation of North America. You can adjust process ink neutral densities to match printing
industry standards in other parts of the world.
The trapping engine derives the ND values for a spot color from its CMYK equivalent. For most spot colors, the ND
values of their CMYK equivalents are accurate enough for proper trap creation. Spot inks that aren’t easily simulated
using process inks, such as metallic inks and varnishes, may need their ND values adjusted so that the trapping
engine can trap them correctly. By typing new values, you can ensure that an ink that is observably darker or lighter
is recognized that way by the trapping engine; the appropriate trap placement is then applied automatically.
You can get the appropriate neutral density value for a given ink by asking your commercial printer. The most
accurate method of determining an ink’s ND value is by measuring a swatch of the ink with a commercial densito-
meter. Read the “V” or visual density of the ink (don’t use process filters). If the value differs from the default setting,
type the new value in the ND text box.
Note: Changing the neutral density for a spot color affects only how that color will trap. It doesn’t change the appearance
of that color in your document.
Follow these guidelines when adjusting ND values:
Metallic and opaque inks Metallic inks are usually darker than their CMYK equivalents, while opaque inks obscure
any ink beneath them. In general, you should set the ND values for both metallic and opaque spot colors much
higher than their default values to ensure that these spot colors won’t spread.
Note: Setting an ink to Opaque or Opaque Ignore in the Type menu of the Ink Manager prevents an opaque ink from
spreading into other colors, unless another opaque ink has a higher ND value.
Pastel inks These inks are normally lighter than their process equivalents. You may want to set the ND value for
these inks lower than their default values to ensure that they spread into adjacent darker colors.