Option
Last updated on
Jun 2, 2026
Trap preset specifications in Adobe InDesign define width values, appearance controls, image handling, and threshold settings.
Consult these specifications when creating or editing trap presets to ensure accurate trapping for your print job. You can access the Trap Preset options by selecting Window > Output > Trap Presets.
Before adjusting these values, consult your commercial printer or prepress service provider. Paper characteristics, screen rulings, and press conditions all affect appropriate trap settings.
Trap Width
Trap width controls the amount of overlap created for each trap. These values directly impact how colors interact at object boundaries.
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Description |
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Default |
Specifies the trap width in points for trapping all colors except those involving solid black.
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Black |
Controls the distance that inks spread into solid black, or the holdback amount (the distance between black edges and underlying inks for trapping rich blacks). A popular option is Neutral Rich Black (40C 30M 30Y 100K). When using any rich black, trapping is less important as there are other process colors within the rich mix.
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Note
When using Application Built-In trapping in InDesign, trap widths exceeding 4 points are automatically limited to 4 points during output. The specified value remains displayed and will be honored if you switch to Adobe In-RIP Trapping.
Trap Appearance
These settings control the geometric shape of traps where trap edges meet or intersect.
Join Style
Controls the shape of the outside join where two trap segments meet at a common endpoint.
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Style |
Description |
Use Case |
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Miter |
Creates sharp, pointed corners |
Default; maintains compatibility with earlier Adobe Trapping Engine versions. |
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Round |
Creates rounded corners |
Softer appearance; useful for curved objects. |
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Bevel |
Creates flat, angled corners |
Prevents extremely sharp points on acute angles. |
End Style
Controls the intersection point where three trap segments meet.
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Style |
Description |
Behavior |
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Miter |
Keeps trap ends away from intersection |
Default; trap terminates before reaching the three-way intersection point. |
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Overlap |
Wraps lightest trap around intersection |
The trap from the lightest neutral density object wraps around the point where three objects intersect. |
Image
These settings determine how InDesign traps bitmap images and how they interact with vector objects.
Trap Placement
Controls where the trap falls when vector objects (including InDesign-drawn objects) abut bitmap images.
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Option |
Behavior |
Visual Result |
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Center |
Trap straddles the edge |
Consistent edge regardless of colors. |
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Choke |
Object overlaps the image |
Vector element spreads into bitmap. |
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Spread |
Image overlaps the object |
Bitmap spreads into vector element. |
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Neutral Density |
Applies standard trapping rules |
Trap may shift sides as colors change; can create uneven edges on photographs. |
Tip
Use Center, Choke, or Spread for visually consistent edges when trapping objects to photographs. Neutral Density can create noticeable uneven edges as the trap shifts from one side to another.
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Option |
Description |
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Trap Objects To Images |
When enabled, ensures vector objects (such as frames used as keylines) trap to images using the Trap Placement settings.
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Trap Images To Images |
Controls trapping along boundaries where bitmap images overlap or butt against each other.
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Trap Images Internally |
Controls trapping among colors within individual bitmap images, not just where they touch vector artwork and text.
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Trap 1-Bit Images |
Ensures 1-bit images trap to abutting objects. This option ignores Image Trap Placement settings because 1-bit images use only one color.
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Trap Thresholds
These values specify the conditions under which trapping occurs. Multiple variables—including ink colors, paper stock, and press conditions—affect appropriate threshold values.
Option | Description |
Step | Specifies the color change threshold at which the trapping engine creates a trap.
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Black Color | Indicates the minimum amount of black ink required before the Black trap width setting is applied.
Useful when compensating for extreme dot gain on low-grade paper stock. |
Black Density | Indicates the neutral density value at or above which InDesign considers an ink to be black.
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Sliding Trap | Determines when the trapping engine begins to straddle the centerline of a color boundary rather than favoring one side.
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Trap Color Reduction | Controls the degree to which components from abutting colors are used to reduce the trap color, preventing traps that are darker than either abutting color.
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Black Trapping Specifications
When creating or editing trap presets, the Black Color and Black Density settings work together to define what qualifies as "black" for trapping purposes.
Solid Black vs. Rich Black
- Solid black: 100% K (black) ink only
- Rich black: Process black (K) mixed with percentages of cyan, magenta, and/or yellow for increased opacity
Black Trap Width Application
The Black trap width value applies when:
- An ink reaches the Black Color percentage threshold, AND
- The ink's neutral density equals or exceeds the Black Density value
Keepaway (Holdback) for Rich Blacks
When support screens (CMY inks) extend to the edge of black areas, misregistration causes visible halos or distorted edges. InDesign uses a keepaway (holdback) to maintain support screens at a specified distance from:
- Reversed-out (knockout) elements in black areas
- Light foreground elements overlapping black
The Black trap width value controls this keepaway distance.
Note
For thin elements (such as black keylines around graphics), InDesign overrides the Black trap width setting and limits the trap to half the element's width.
Setting Sliding Traps
Sliding traps prevent visible trap lines by moving the trap position based on the neutral density relationship between abutting colors.
Effect of different values:
- 0%: All traps default to centerline position
- 70% (default): Trap straddles centerline when lighter color exceeds 70% of darker color's neutral density
- 100%: Sliding traps disabled; one color always spreads fully into another regardless of neutral density
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