Instead of the usual trapping of a light color into a dark color, you can use a centerline trap. A centerline trap is a trap that is placed in the middle of two objects that have similar values for neutral density.
You can use the centerline trap limit to control whether centerline traps are created between objects with similar values for neutral density.
Note: You cannot add a centerline trap between black or opaque inks.

1. In PDF Trap Editor, select the Detailed view of the Trap Page or Trap Selection dialog box.
2. Click the General tab.

3. In the Centerline Trap Limit box, type a value.
   The range is from 0 to 100 percent.

   Centerline Trap Limit	Result
   100 percent (default)	No centerline traps unless adjacent objects have exactly the same value for neutral density
   Higher values	Adds a centerline trap between colors with similar values for neutral density
   Lower values	Adds a centerline trap between colors with different values for neutral density
   0 percent	Almost all traps will be centerline traps