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Using the Trap command


    The Trap command creates traps for simple objects by identifying the lighter artwork--whether it's the object or the background--and overprinting (trapping) it into the darker artwork.

    Note: The Trap command is only available when you are working on CMYK documents.

    Illustration of function of Trap command with these callouts: A. Area of overprint B. Area of knockout C. Background color D. Foreground color
    Function of Trap command A. Area of overprint B. Area of knockout C. Background color D. Foreground color

    You can apply the Trap command as a Pathfinder command or as an effect. For more information on effects, see Using effects. For instructions on using the Stroke palette to create a trap with strokes on individual objects, see Trapping by overprinting.

    In some cases, the top and bottom objects may have similar color densities so that one color is not obviously darker than the other. In this case, the Trap command determines the trap based on slight differences in color; if the trap specified by the Trap dialog box is not satisfactory, you can use the Reverse Trap option to switch the way in which the Trap command traps the two objects.

    Light object and dark background: Trap command creates spread. Dark object and light background: Trap command creates choke.
    Light object and dark background: Trap command creates spread. Dark object and light background: Trap command creates choke.

To create a trap using the Trap command:

  1. Select two or more objects, choose Window > Pathfinder, and select Trap from the palette's pop-out menu.
  2. In the Thickness text box, enter a stroke width of between 0.01 and 5000 points. Check with your print shop to determine what value to use.
  3. Enter a value in the Height/Width% text box to specify the trap on horizontal lines as a percentage of the trap on vertical lines.
  4. Specifying different horizontal and vertical trap values lets you compensate for on-press irregularities, such as paper stretch. Contact your print shop for help in determining this value. The default value of 100% results in the same trap width on horizontal lines and on vertical lines.

    To increase the trap thickness on horizontal lines without changing the vertical trap, set the Height/Width value to greater than 100%. To decrease the trap thickness on horizontal lines without changing the vertical trap, set the Height/Width value to less than 100%.

    Height/Width set to 50% and 200%
    Height/Width set to 50% and 200%
  5. Enter a Tint Reduction value to change the tint of the trap. The default value is 40%.
  6. The Tint Reduction value reduces the values of the lighter color being trapped; the darker color values remain at 100%. The Tint Reduction value also affects the values of custom colors.

    With tint reduction value of 100%, trap contains 100% of lighter color. With tint reduction value of 50%, trap contains 50% of lighter color.
    With tint reduction value of 100%, trap contains 100% of lighter color. With tint reduction value of 50%, trap contains 50% of lighter color.
  7. Select additional trapping options as required:
    • Traps with Process Color if you want to convert spot color traps to equivalent process colors. This option creates an object of the lighter of the spot colors and overprints it.
    • Reverse Traps to trap darker colors into lighter colors. This option does not work with rich black--that is, black that contains additional CMY inks.
  8. Click OK to create a trap on the selected objects. Click Defaults to return to the default trapping values.