8.5

on a printed page, the direction of the trap is determined by the relative luminance (lightness
or brightness) of the colors.
An object color can be trapped to a background color in four ways:
• Overprint: When the object color prints directly on top of a background color.
• Knockout: When the object color cuts out (knocks out) its own exact shape from the
background color.
• Spread: When the lighter object color is slightly enlarged so the object shape overlaps the
darker background color.
• Choke: When the darker object color is slightly reduced so that the shape of the background
color overlaps the object color
Trapping values in QuarkXPress are determined in one of three stages:
• Default trapping is the default method that QuarkXPress uses to automatically trap colors
of varying hues and shades, based on the relative luminance of object and background
colors. Use the Trapping pane of the Preferences dialog box (QuarkXPress/Edit >
Preferences) to enter default trapping preferences for QuarkXPress and for individual
QuarkXPress layouts (layout-specific trapping).
• Color-specific trapping is trapping that is specified for any object color relative to any
background color. By specifying Overprint, Knockout, Auto Amount (+) for spreads,
Auto Amount (–) for chokes, or Custom trap values in the Trap Specifications dialog
box (Edit > Colors > Edit Trap), you can control the trapping relationships for every color
in your Colors palette (Window menu).
• Item-specific trapping is trapping that is specified for any item using the Trap Information
palette (Window menu).
Document-specific preferences override default preferences, color-specific preferences
override all default preferences, and item-specific preferences override all other trapping
preferences.
If you are printing composite (no separations) or are printing to a laser printer, specifying
trapping values will have no effect on your output.
The trapping values you specify should be determined by the press, paper, sheet size, inks,
and line screen (lpi) that will be used to produce your job. For best results, use the trapping
method and values your service bureau and printer recommend.
Trapping EPS pictures
Trapping settings (overprints and knockouts) in imported EPS files are honored when you
put such pictures in front of other QuarkXPress items.
A GUIDE TO QUARKXPRESS 8.5: PLUS EDITION | 235
OUTPUT