You can change trap preset options whenever you create or edit a trap preset. The same trap preset options are available in Acrobat and InDesign. In Acrobat, you can view trap presets by choosing Tools > Print Production > Trap Presets. In InDesign, choose Window > Output > Trap Presets.
Trap width is the amount of overlap for each trap. Differences in paper characteristics, screen rulings, and printing press conditions require different trap widths. To determine the appropriate trap widths for each job, consult your commercial printer.
In InDesign, the value you set for Black Color determines the value for a solid black or a rich black, a process black (K) ink mixed with color inks for increased opacity and richer color.
A join is where two trap edges meet at a common endpoint. You can control the shape of the outside join of two trap segments and the intersection of three traps.
To change how much the component inks in abutting colors can vary before causing those colors to trap, increase or decrease the value for Step in the New Trap Preset or Modify Trap Preset Options dialog box. The default is 10%. For best results, use a value from 8% to 20%. Lower percentages increase sensitivity to color differences and result in more traps.
You can create a trap preset to control traps within images, and to control traps between bitmap images (such as photographs and those saved in raster PDF files) and vector objects (such as those from a drawing program and vector PDF files). Each trapping engine handles imported graphics differently. It’s important to be aware of these differences when setting trapping options.