Trap with PowerTrapper

The advantage of using a PowerTrapper is that you do not have to prepare the PDF file or create the trap layer in advance. In addition, you can trap the input file without an intermediate file. The output of this task is a Normalized PDF file.

You can choose your trapping settings in the Distance & Direction, Color & Shape, Processing, Rules and Output tabs.

Distance & Direction

You can set the trapping distance and direction at the tab Distance & Directions.



  1. Trapping
    You can choose between two trapping modes:
    • Normal Trapping: This selects adjoining color pairs, which are likely to cause registration problems like ugly light gaps, and unwanted halo effects. Lighter colors are generally trapped into darker colors to minimize the visual effect of the trap.
    • Reverse Trapping: This prevents overprint of adjoining color areas by trapping these color pairs with a white knockout (erasing) trap. The white knockout trap is put on top of the lighter of the two colors. This is useful to prepare a job for Dry Offset printing (example: metal beverage cans). This avoids overprinting of inks.
  2. Trapping Distance

    Enter the width you want to give your traps. The unit used is the General unit defined in Illustrator's Unit & Display Performance Preferences. The default trap width is 0.2 mm (or equivalent in your chosen unit).

    You can choose more trapping distance specifications such as: into black, into spot, into image and into pullback further down in this tab.

  3. Minimum Ink Difference
    Trapping is applied to two adjoining colors when either:
    • The two colors each consist of at least one ink but they have no common inks.
    • The two colors have common inks but there is a difference of at least the Minimum Ink Difference percentage for two or more inks making up these colors.
    These differences in ink percentages must be in opposite directions.

    For example, with the default minimum ink difference percentage of 10%, the following two colors are trapped:

    1st color: C 5% M 10% Y 50% K 15% (+10% K)

    2nd color: C 5% M 10% Y 85% K 5% (+35% Y)

    Increase the Minimum Ink Difference to trap colors that differ more, lower it to trap colors that are similar.

  4. Image Trapping
    • Automatic (default): this determines the most suitable trap direction automatically, by comparing the average lightness of the CT image with the lightness of the adjoining area, then traps the lighter color into the darker one.
    • Always Towards Images: this always traps line art under adjoining CT images.
    • Always Towards Line Art: this always traps CT images under adjoining line art.

    If you want images to be trapped with each other, enable Trap images to images.

  5. Pull Back

    You can use ink pull back to keep away all but the darkest ink of a color area composed of multiple inks bordering to a very light background. It prevents individual inks from the composed color to become visible on the background due to registration errors during the printing process.

    • Automatic (default): this creates pull backs on rich black or rich spot colors, when the color left in the pull back area is not very different from the composed color.
    • Only Pull Back Rich Black: this only creates pull backs on rich black.
    • Do Not Pull Back: this never creates any pull back.

    There will be automatic pull back for the darkest color. You can enable Also pull back light inks option to create pull backs even when the pullback ink (ink remaining in the pull back area) is visibly different from the composed color. Enable Pull back images and gradients to create pull backs on images and gradients.

  6. Treat all spot colors as opaque inks

    You can enable this option to set the trapping direction by ink sequence. PowerTrapper uses the color luminance to define the trapping direction by default except for opaque inks. PowerTrapper uses ink sequence to determine trapping direction in the case of opaque inks. If the Treat all spot colors as opaque inks option is enabled, color luminance is used only for CMYK. For opaque and spot inks, the trap direction is determined by the ink sequence.

  7. Overshoot Mode
    You can choose between the following three overshoot modes:
    • Automatic (default): The centerline behavior is according the rules determined in the color pair list.
    • Never on Dark Areas: The centerline is forced not to get beyond the center of dark areas.
    • Never: The centerline is forced not to get beyond the center of any area.

Color & Shapes





  1. Trap Color Intensity

    By default, PowerTrapper uses the full color of the object to spread in the trap (100% trap color intensity).

    You can create a trap of a lighter color by reducing the trap color intensity percentage.

  2. Image Trap Color
    Choose how to trap your images:
    • Use Original Image Data (default): When spreading an image, PowerTrapper uses the underlying image data (when the image is clipped) to create the trap.
      Note: An empty trap is created, when there is no underlying image data (when the image is not clipped).
    • Extend Image Data: PowerTrapper automatically extrapolates the image along its top, right, bottom and left edges to ensure that the trap looks as expected even if there is no clipped image data outside the visible image.
    • Use an Approximate Flat Color: Instead of using existing or extrapolated image data in the trap, PowerTrapper uses a solid color. A suitable color is determined by averaging the image's colors along its boundary with the object to trap.
  3. Truncate Traps
    PowerTrapper can truncate the trap so that it does not stick out on another color. There are two truncation modes:
    • On Center (default): when a portion of a trap comes too close to the contour of another object, PowerTrapper limits it to half the distance between the trapped object and the other object.
    • On Edge: when a portion of a trap comes too close to the contour of another object, it is truncated on the other object's edge.
  4. End Caps
    This option specifies how to shape the ends of an open trap.
    • Square (default): this option ends the trap at right angle to the adjoining object.
    • Round: this rounds the ends of the trap. This option is typically only used in combination with white knockout (reverse trapping).
      Note: We recommend that you do not to use Round End Caps together with Truncate Traps On Center, as this can generate some artefacts (the round caps are truncated).
    • Object Dependent: with this option, the trap is a logical continuation of the contour of the spread object.
  5. Trap Corners
    This option allows you to change how the traps’ sharp corners are handled.
    • Round (default): a round cap will be placed at all corners.
    • Beveled: this cuts sharp corners off.
    • Mitered: this option works with a miter ratio.

      The miter ratio serves to limit the length of the sharp corner (the distance from the base of the trap to the corner point).

      The default miter ratio value is 4. This means that if the length of the sharp corner is more than 4 times the Trapping Distance, then the corner are cut off (beveled). If it is less than 4 times the Trapping Distance, the corner are left as it is.

  6. Advanced Settings

    Click the collapsible button to show the advanced settings.

    Truncate Traps

    If you want to truncate traps into black differently, select Into black and choose the truncation mode (On Center or On Edge).

Processing

  1. Color pairs
    PowerTrapper can trap all hits (occurrences) of a color pair the same way or recalculate the trap direction for different hits.
    • Each hit can have its own decision (default): this recalculates the trap direction for each hit of a color pair.
    • Use the same decision for all hits: this traps all hits of the same color pair in the same direction.
    • Use the same decision for objects smaller than: this uses the same trap direction for hits of a color pair belonging to small objects, and recalculates the trap direction for hits belonging to bigger objects.
    Use the field next to the option to determine the maximum size of small objects. The unit used is the General unit defined in Illustrator's Unit & Display Performance Preferences.

    The default size is 1 mm (or equivalent in your chosen unit).

  2. Objects
    In some cases PowerTrapper can safely ignore certain object types to speed up the trapping.
    • Only selected objects
    • Respect existing traps: if your document has already been trapped, select this option to keep the existing trap layer out of the trapping process.
    • Ignore bitmaps: this keeps bitmap pixel data from being trapped. Bitmap data is contourized before trapping which may slow down trapping depending on the bitmap's contents. Bitmaps with lots of small isolated islands typically take a longer time to trap.
      Note: When you indicate an object type to ignore, it is ignored completely as if it did not exist in the job. Also, the ignored objects does not truncate trapping areas resulting from other objects below them.
  3. Small Gaps

    Some input jobs contain very small unintentional gaps between neighboring objects, preventing the correct trapping of these objects. Although it is better to clean up such jobs before trapping, PowerTrapper can ignore these gaps automatically.

    To use this option, select Close when smaller than and enter the maximum size small gaps can have.

    The unit used is the General unit defined in Illustrator's Unit & Display Performance Preferences.

    The default size is 0.01 mm (or equivalent in your chosen unit).
    Note: If you set a big gap size, trapping may become slower and small parts of the job may be ignored during trapping.

Rules

You can define custom trapping settings for specific trapping pairs using the Rules tab.
  1. When to use rules?

    In most cases the general trapping settings entered in the Distance &Direction gives you excellent results. You can refine them using rules. If you add a rule that is not coherent with your inputs in the other tabs, PowerTrapper will overwrite them with the rules

    Note: This is an advanced feature and we recommend it for experienced users.

    You can specify exceptions to the general trapping settings for certain color pairs using Add Rule. Some of the instances where you can use it are :

    • to set a different trap distance for a specific spot ink. Sometimes you need a larger trap distance for spot inks if there is no other ink to help cover leaks on the press.
    • to prevent trapping or ink pull back in specific cases. Depending on the type of the adjoining colors, trapping and / or pull back may be undesirable.
    • to force a specific trap direction. PowerTrapper Standalone determines the trap direction based on the relative lightness of the adjoining colors. If the colors have a similar lightness level, it selects an arbitrary direction. You can use a rule to make it always use a particular direction for a color pair.
    • to specify a different shape and/ or truncation mode for certain color pairs. For example, you can choose to use “On Center” truncation when trapping under a 100% black line and “On Edge” truncation on all other color pairs.
  2. Creating a rule



    • Click the Add Rule button at the bottom of the Rules tab.
    • In the pop-up that opens, choose the trapping pair to apply the rule to using the From and To lists. You can create a rule to trap from/to: any color, a particular ink (process, spot or opaque), a particular object (image, gradient or empty background) or the registration color.
      Note: When trapping a particular ink, you can choose the ink name from which Minimum Density the rule is applied and if the color must be pure (no other separation in the color object) to apply the rule.
    • Choose the contents of the rule.
      Options Description
      Trapping Direction
      • Automatic lets PowerTrapper Standalone calculate the trapping direction.
      • Force Trapping from ‘From’ to ‘To’ always spreads the “From” color/object on the “To” color/object.
      • Do Not Trap ‘From’ to ‘To’ never traps the “From” and “To” colors/objects together.
      Trapping Distance Use this to define a special trapping distance for the trapping pair.
      Trap Color Intensity Use this to define a special trap color intensity for the trapping pair.
      Pull Back
      • Automatic lets PowerTrapper decide if there should be a pull back on the trapping pair.
      • Always Pull Back always creates a pull back on the trapping pair. The darkest ink of the pair is the pullback ink (remaining ink in the pull back area).
      • Do Not Pull Back never creates a pull back on the trapping pair.
      Pull Back Distance Use this to define a special pull back distance for the trapping pair.
      Reverse
      • Automatic lets PowerTrapper Standalone decide if the trapping pair should have a reversed trap.
      • Always Trap Reversed always generates a reversed trap for the trapping pair.
      • Do Not Trap Reversed never generates a reversed trap for the trapping pair.
      Truncate Traps Choose if traps generated for the trapping pair should be truncated on center or on edge.
      End Caps Choose how to shape the ends of open traps for the trapping pair (square, round or object dependent).
      Trap Corners Choose how to shape the trapping pair's trap corners (round, beveled or mitered).
    • If necessary, use the + button to add contents to your rule. You can use the - button to remove contents.
    • After defining the rules, click OK button. You can now see your rule at the Rules tab.

    When trapping your document, PowerTrapper traps the trapping pairs that match rules according to those rules and the rest of your document according to the main trapping settings. If necessary, you can add another rule or remove a rule previously created. You can also edit a rule by double-clicking it in the Rules tab.

Output

You can specify the output at Output tab. You can enable Trap layer only or Load trap color pairs if present or enable both

See also: What is trapping?

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