When exporting a PDF file, the InDesign window is divided into several sub-items. The details relevant to risography will now be explained in detail:
In addition to the settings Standard / PDF compatibility, correctly choosing whether pages or sheets are used is essential. Options like fast web view, PDF tags and embed page thumbnails should be avoided, as well as the inclusion of interactive elements.
It is recommended that you export files in one of the PDF / X standards, for example, PDF / X-3: 2002. The PDF / X standard prohibits many file contents by default because they may be unsuitable for reproduction. PDF elements that negatively affect the work of the RIP and thus the predictability of the print result, for example, are prohibited.The functions that PDF / X considers during creation include the removal of notes / comments in the printable area, a defined bleed and defined final format, checking if all images are incorporated correctly and the deactivation of security functions, so the file can be reproduced by anyone. Although the PDF / X-3 standard is a little old, it is completely sufficient for risographic reproduction.
Adobe mentions their own compatibility levels of their files on their website as: “Generally speaking, unless there’s a specific need for backward compatibility, you should use the most recent version (in this case version 1.7).” Unfortunately, in risography, there is a specific need for PDF file to always be compatible with Acrobat 4 (PDF 1.3). This, just like the compatibility to Acrobat 5, prevents PDF files from containing layers. Compatibility to Acrobat 5, however, already supports live transparencies in the image, which should be strongly avoided to avoid unwanted printing results.
The usual compression settings should not be changed; all images should be compressed to 300 or 1200dpi and scaled down at maxi-
mum quality with JPG compression.
In the menu “Marks and bleed” most options can stay disabled. For an accurate perfecting, the print file needs printing as well as registration marks. In order to position the printing marks far enough apart and to prevent any flashes in case of registration inaccuracies, the offset should be increased from the usual 2.117 mm (6 pt in mm) to at least 3 mm, and if the image allows it, the bleed can be increased from 3 to 5 millimetres. If there is enough room around the image, they can be increased even further, but this could possibly cause it to look too cluttered. The thickness of these registration marks should be 0.25 pt: 0.125 pt may be too fragile for print, 0.5 pt may be too inaccurate to align exactly with the pass marks. The colour bar is not needed when creating the colour separations. To save colour, it can simply be disabled. The image itself implicitly requires at least 3 mm of bleed, since 3 mm is the printing tolerance used in the printing industry that is needed for production-related reasons. Since the inaccuracies in risographs can turn out stronger depending on the method of operation and printer type, it is highly recommended to include 3 or even 5 mm of bleed into the image. The graphics of the subject should be planned with this edge in mind and background areas should be enlarged up to this bleed in order to guarantee the best possible result. This applies to duplex printing procedures, in order that there is enough leeway in case of registration inaccuracies.
What is important about the output is that the files are not converted into a target profile and most importantly not in one that is not a greyscale profile. Although there is a very good greyscale printing profile by basICColor and also a greyscale profile for Black colour published by Exploriso.info, the user should be aware of the consequences. For a large number of users, it is easier and, above all, sufficient to convert the existing images into greyscale from RGB or CMYK using Photoshop and not use any profiling in the InDesign export dialogue.
The function “Subset fonts when percent of characters used is less than: 100%” can help keeping the PDF file as small as possible. It also ensures that only urgently needed glyphs that are really needed are transferred to the printer, to make sure the RIP is not unnecessarily burdened. This becomes particularly relevant when working with a well-built font that contains a particularly large number of ligatures and / or special characters. Depending on the RIP unit, the number of glyphs can significantly slow down the work on multi-page PDFs containing high resolution image content.
Transparencies must always be converted or reduced when converting from layout to PostScript or PDF. Working with a risograph, however, one should make this reduction in advance, or not work with transparencies at all. This is because they need to keep in mind the possibility that reducing the transparency may change objects on the page or that the risographs RIP may interpret hairlines as page elements. If working with transparencies cannot be avoided, the reduction should take place using a high resolution. Additionally, differing settings should not be ignored, but preferably disabled.