The Settings and Inks sections of the Trapping tab decide how wide the traps are, which colour spreads into which, and how each ink behaves. Settings save on their own and mark the traps in the file out of date; they never re-run trapping. Run trapping again to use them (see Trapping).
Presets#
A preset sets every trapping setting for one kind of press; pick the one that matches the press, then change what you need.
| Preset | For |
|---|---|
| Offset | Sheetfed and web offset: 0.09 mm traps, 0.18 mm into black. The default. |
| Flexo | Flexo, with its looser register: 0.2 mm traps, 0.3 mm into black, opaque white pulled back 0.127 mm, and the first printable dot in highlights. |
| Digital (no traps) | Digital presses print in register: no traps are made, and traps already in the file are switched off. |
| Custom | Offset or Flexo with your own changes. |
Change any setting of Offset or Flexo and the preset becomes Custom, starting from that preset ("Custom, starting from Offset"). Picking a preset again drops your changes.
The main settings#
Five settings are shown straight away: Trap width, Width into black, Step limit, Image placement and Sliding trap limit. The others are under Advanced, in the groups Rules, Black and keepaway, Images, Small objects, Flexo and Detection. Each field shows the value in use, and many have a help line under them; the table below explains every setting. Setting a field back to the preset's own value drops that change.
Every setting#
| Setting | Group | Offset | Flexo | Range | What it does |
|---|---|---|---|---|---|
| Trap width | Widths | 0.09 mm | 0.2 mm | 0.01 to 1 mm | How far the lighter colour spreads into the darker one. |
| Width into black | Widths | 0.18 mm | 0.3 mm | 0.01 to 1.5 mm | How far colours spread under solid black. |
| Step limit | Rules | 0.1 | 0.1 | 0 to 5 | How much two touching colours must differ, relative to the lighter ink, before they are trapped. |
| Sliding trap limit | Rules | 0.7 | 0.7 | 0 to 1 | When the lighter colour is at least this dark relative to the darker one, the trap moves to straddle the edge. |
| Width into spot colours (0 = trap width) | Rules | 0 mm | 0 mm | 0 to 1 mm | The trap width where a spot colour is the darker ink of the edge. |
| Horizontal width scale | Rules | 1× | 1× | 0.25 to 4× | Multiplies trap widths across the page, for a press that misregisters more in one direction. |
| Vertical width scale | Rules | 1× | 1× | 0.25 to 4× | Multiplies trap widths up and down the page. |
| Minimum ink step (absolute) | Rules | 0.05 | 0.05 | 0 to 1 | The smallest tint difference (0–1) that counts as two colours differing. |
| Common density limit | Rules | 0.5 D | 0.5 D | 0 to 4 D | No trap when the ink both colours share is this dark: it hides any gap. |
| Paper density limit | Rules | 0.005 D | 0.005 D | 0 to 0.2 D | Colours lighter than this count as paper and are not trapped. |
| Trap colour intensity | Rules | 1× | 1× | 0.1 to 1× | The trap's tint as a share of the colour that spreads. |
| Black colour limit | Black and keepaway | 0.95 | 0.95 | 0.5 to 1 | The tint from which a dark ink counts as solid black. |
| Black density limit | Black and keepaway | 1.6 D | 1.6 D | 0.5 to 4 D | How dark an ink must be (density) to count as black. |
| Rich black keepaway | Black and keepaway | Rich black | Rich black | Rich black, Off | Pull the colours under a rich black back from its edges so they cannot show. |
| Keepaway width | Black and keepaway | 0.18 mm | 0.3 mm | 0 to 1.5 mm | How far the colours under a rich black are pulled back from its edges. |
| Image placement | Images | Centre | Centre | Centre, Into the object, Into the image, Normal | Which side the trap goes on where objects meet images. |
| Width at images (0 = trap width) | Images | 0 mm | 0 mm | 0 to 1 mm | The trap width where an object meets a placed image. |
| Trap images to objects | Images | On | On | On or off | Trap where objects meet images. |
| Trap images to images | Images | On | On | On or off | Trap where two images meet. |
| Trap inside images | Images | Off | Off | On or off | Also trap colour edges inside images; off, edges inside an image are left alone. |
| Small text up to | Small objects | 6 pt | 6 pt | 0 to 24 pt | Text this size or smaller counts as small text. |
| Small text width scale | Small objects | 0.75× | 0.75× | 0.1 to 1× | The trap width on small text, as a share of the normal width. |
| Small object protection (per side) | Small objects | 0.33× | 0.33× | 0.05 to 0.5× | A trap never covers more than this share of a small object's width. |
| Do not trap objects thinner than | Small objects | 0.03 mm | 0.05 mm | 0 to 1 mm | Hairlines thinner than this are not trapped. |
| Thin objects spread when under | Small objects | 1.5 × width | 1.5 × width | 0 to 5 × width | Objects thinner than this many trap widths (not black, not an image) spread outwards instead of being choked away. |
| Thin object spread | Small objects | 0.5 × width | 0.5 × width | 0 to 1 × width | How far such a thin object spreads outwards, in trap widths. |
| Same decision for objects under | Small objects | 1 mm | 1 mm | 0 to 10 mm | Areas narrower than this follow the decision of the colours around them. |
| Opaque underprint choke | Flexo | 0 mm | 0.127 mm | 0 to 1 mm | How far an opaque underprint, such as white, is pulled back from the colours printed over it. |
| Second underprint extra choke | Flexo | 0 mm | 0.05 mm | 0 to 1 mm | Extra pull-back for each further underprint. |
| First printable dot in highlights | Flexo | 0 | 0.02 | 0 to 0.2 | Tints lighter than this count as the first printable dot when traps are decided. |
| Truncation | Detection | Centre | Centre | Centre, On edge | Where a trap stops when it meets a third colour. |
| Close gaps under | Detection | 0.01 mm | 0.01 mm | 0 to 0.1 mm | Slivers narrower than this between objects are treated as touching. |
| Detection resolution | Detection | 1200 ppi | 1200 ppi | 600 ppi (draft), 1200 ppi, 2400 ppi | Resolution used to find the edges; higher is slower. |
| Darken blend (for PDF viewers) | Detection | Off | Off | On or off | Makes PDF viewers without overprint preview show the traps darker, not wrong. |
Widths are in millimetres (1 mm is about 0.04 in). With Detection resolution at 1200 ppi and a Trap width under 0.08 mm, traps are found at 2400 ppi, so they stay a few pixels wide.
Inks#
The Inks table lists the process inks, the spot colours and the technical layers of the page, each with a Kind and an ND.
| Kind | What it means |
|---|---|
| Normal | Lighter inks spread into darker ones, by neutral density (ND). |
| Transparent | Varnish, spot UV, emboss: never trapped. |
| Opaque | Foil, metallic, opaque white: never spread; other inks spread under them. |
| Ignored | Gives and receives no traps. |
| Technical | Cut, crease and other lines that never print. |
The kind is filled in for you, and you can change it:
- inks with a technical line type are Technical, locked ("set by its line type");
- inks with the Varnish line type, or a varnish, spot UV, soft-touch, emboss or deboss finish in 3D (or a name that says so) are Transparent;
- inks with the Foil line type, a foil or white finish, or a metallic name (gold, silver, copper, pearl…) are Opaque. White is laid down first and foil last.
ND (neutral density) is how dark the ink prints, which decides which colour spreads. Leave it blank to have it measured from the ink's colour; the measured value shows in grey. Type your own from 0.001 to 4 for a spot colour that prints darker or lighter than its swatch.
The table uses the ink names of the original file. Inks renamed on the Tools tab keep their settings; hover a row to see the name in the print-ready file.
The API takes the same settings: see Prepress API.