Quick links to procedures on this page:
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When colors are trapped, they are intentionally overlapped so that misalignments of print separations are not noticeable. In manual trapping, one color must overprint the other. Overprinting is achieved by printing one color over another. Overprint trapping works best when the top color is much darker than the underlying color; otherwise, an undesirable third color may result (for example, cyan over yellow results in a green object). In some cases, you might actually want to create a third color; for example, you can overprint two spot colors to create a third color.
How overprinted colors mix depends on the type of colors and ink you are mixing and the types of objects you are overprinting. For example, an object that uses a CMYK color overprints differently from an object that uses a spot color. Bitmaps also overprint differently from vector objects. You can preview a simulation of how overprinted colors will mix by enabling the Enhanced viewing mode and the Simulate overprints viewing mode. For more information about choosing a viewing mode, see Choosing viewing modes. Some variation between the preview and the printed version may occur, depending on the printer you use.
When you are ready to print, you can choose to preserve overprint settings if you want to trap objects in a document, or if you want to mix the overlapping colors for effect. You can also choose to knock out the overprinted areas so that only the top color is visible. If you want to print a proof version of the file, you can simulate overprints. Simulating overprints rasterizes the file, and it prints using process colors only.
You can set a group of objects to overprint. You can allow text to overprint overlying objects. You can also overprint bitmaps; or each vector object’s fill, or outline, or both. In addition, you can overprint specific color separations and specify in which order they will print, as well as whether you want to overprint graphics, or text, or both.
The two methods for automatic color trapping include always overprinting black and auto-spreading. Overprinting black creates a color trap by causing any object that contains 95% black or more to overprint any underlying objects. This option is useful for artwork containing a lot of black text, but it should be used with caution on artwork with a high graphics content. You can adjust the threshold, if the print service provider recommends a black threshold value other than 95%.
Auto-spreading creates color trapping by assigning an outline to an object that is the same color as the object’s fill and having it overprint underlying objects. Auto-spreading is created for all objects in the file that meet three conditions: they do not already have an outline, are filled with a uniform fill, and have not already been designated to overprint.
For advanced trapping options, see Specifying In-RIP trapping settings.
| To preserve or ignore overprints when printing | |
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Click File  Print.
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Click the Color tab.
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Choose one of the following options:
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Print composite
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Print separations
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Click one of the following tabs:
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Separations
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Composite
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From the Document overprints list box, choose one of the following options:
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Ignore — does not overprint areas; color on top prints and underlying colors are
knocked out
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Preserve — preserves overprinted areas
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| To print a simulated overprint | |
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Click File Print.
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Click the Color tab.
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Enable the Print composite option.
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Click the Composite tab.
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From the Document overprints list box, choose Simulate.
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The Simulate option rasterizes the file; the file is printed with process colors. |
| To overprint selected objects | |
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Select an object.
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Click Edit, and choose any of the following:
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Overprint outline
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Overprint fill
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Overprint bitmap
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You can also set an object to overprint by right-clicking the object and
choosing an overprint option from the context menu.
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| To overprint selected color separations | |
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Click File Print.
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Click the Color tab.
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Enable the Print separations option.
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Click the Separations tab.
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In the Options area, enable the Use advanced settings check box.
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Click Advanced.
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In the Advanced separations settings dialog box, choose a color separation from
the Screening technology list box.
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In the Overprint column, click one or both of the following icons:
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Overprint graphics
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Overprint text
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The icons appear darker when the separation is set to overprint.
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You can change the order in which color separations print by selecting a color
separation and choosing an order from the Order list box.
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| To trap by always overprinting black | |
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Click File Print.
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Click the Color tab.
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Choose one of the following options:
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Print composite
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Print separations
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Click one of the following tabs:
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Separations
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Composite
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In the Options area, enable the Always overprint black check box.
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| To set the overprint black threshold | |
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Click Tools Options.
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In the list of categories, double-click Global, and click Printing.
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Choose Overprint black threshold (PS) from the Option list.
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Choose a number from the Setting list box.
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The number you choose represents the percentage of black above which black objects overprint. |
| To trap by auto-spreading | |
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Click File Print.
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Click the Color tab.
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Choose one of the following options:
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Print composite
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Print separations
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Click one of the following tabs:
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Separations
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Composite
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In the PostScript trapping or Trapping area, do one of the following:
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Enable the Auto-spreading option, and type a value in the Maximum box.
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Enable the Fixed width option, and type a value in the Width box.
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Type a value in the Text above box.
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The value that you type in the Text above box represents the minimum size to
which auto-spreading is applied. If you set this value too low, small text may
be rendered illegible when auto-spreading is applied.
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The amount of spread assigned to an object depends on the maximum trap
value specified in the Maximum box and the object’s color. The lighter the
color, the greater the percentage of the maximum trap value. The darker the
color, the smaller the percentage of the maximum trap value.
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