Page 158 - Graphic Design and Print Production Fundamentals

146 Chapter 5. Pre-press
Another strategy that must be considered for processing multiple transparent page elements is allowing
the page layout software to raster the page elements, so it sends raster data to the RIP. This technique
treats the transparent elements, such as a photograph on the page, and allows the creator to choose the
resolution of the raster. Care must be taken here to ensure overlapping vector elements will raster at the
same resolution in the RIP. Let’s say we have a type block that crosses a photo on the page, but it is
transparent to let the photo show through the type. If we rasterize the transparent type at 300 ppi — the
resolution of the photo — it will be significantly different from the raster of the vector type at the RIP,
which might be 3,000 lspi for some plate-setters. The letter shape will be 10 times thicker over the photo,
and that will be VERY noticeable if the type crosses the photo in the middle of the glyph. The solution
is to make sure to raster the transparent type at 3,000 ppi to match the plate-setter raster. This makes
the PDF file very large because it contains lots of raster data. But this solution is also a disadvantage
because it does not allow late-stage editing of the transparent values in the PDF file. The advantage is
that the transparency elements will have better WYSIWYG, process more consistently in multiple RIPs,
and use less RIP resources in processing.

It is very important to be aware of the transparent elements you are creating in a document. It is not
always apparent when using effects, plug-ins, or effects filters available in page layout software. Using a
bevel or emboss effect, or a simple drop shadow, makes that page element use transparent routines in the
RIP. Programs like Adobe InDesign let designers view all the transparent elements on a page. Designers
should examine each one to decide if it should be rasterized before RIP-ing or at the RIP. This is a good
point at which to decide if transparent elements can be grouped, or organized, on common layers. It is
also a good point to decide how the transparent element contributes to the design, and how critical the
level of transparency, or WYSIWG value, is in the overall design. In the retrospective book cover design
referred to above, WYSIWYG is very important in communicating the message of the book and getting
predictable results.

Transparent elements can be rasterized at the page layout stage, the PDF creation stage, and at the RIP
stage for the final output device. Adobe Acrobat also has a tool to view transparent elements in a PDF
file. It is important for a designer to compare the transparent elements in the PDF to those in the page
layout software. The primary concern is that the elements rasterized in the PDF are no longer editable, so
it is critical that the levels are right to create the desired overall effect. It is also important for a preflight
operator to view the transparent elements in a PDF file to check what the RIP will have to process and
to make sure the computational resources are available. If there are processing errors in the final output,
they are most likely to occur in rendering the transparent objects. Viewing the transparent elements on a
page in Acrobat should provide a mental checklist for the operator when she or he views the final output.

Communication Is Key

The graphic communications industry still has collaborative work to do to make the processing of
transparent elements on a page more predictable and repeatable. It is important for designers to
understand the problems they can be creating for a RIP, especially for output on an extremely high-
resolution device like a plate-setter for waterless lithography. It is also important for operators who are
managing documents with lots of transparency to be aware of the checkpoints in a document, and to
know when there is not adequate WYSIWYG for the transparent elements on a page. Good questions
for all stakeholders to ask when processing a document that relies on many transparent elements are: