to compensate for poor registration on press. Each colour can have its own custom trapping, and blocks of colour can eiyher ‘knock out’ any underlying graphics or over print them (black normally overprints). Even if you set your own trapping preferences in your DTP software-perhaps for a one-off purpose such as ensuring a black graphic knocks out – you may find the imagesetting RIP overrides them. Although Adobe Acrobat now allows you to preview separations and overprints in PDFs on screen, not all RIPs meet the latest PDF standards. Here the designer, bureau (if any) and printer must all work together to get the right result.