Page 157 - Graphic Design and Print Production Fundamentals

5.5 Transparency

Wayne Collins

The biggest challenge in reproducing computer graphics on output devices in today’s marketplace is
dealing with transparency in graphic files. This truly emphasizes the importance of WYSIWYG in
proofing for the graphic communications industry. We must first emphasize that page layout graphic
software is not developed for producing documents for mechanical reproduction. This software
prioritizes the creation of documents for viewing on electronic media; they are created on a computer
screen for viewing on a computer screen. We have reviewed some of the issues with rasterizing vector
shapes consistently, and reliably representing colour from one device to another. Viewing a graphic
with three-dimensional transparent elements is significantly different on an illuminated medium where
the light is transmitted compared to an opaque medium where the light is reflected. It is very hard to
judge how the transparent effects will translate from one to another. There is room for the same kind
of collaborative research in this realm, as there was in developing OpenType font architecture and ICC
profiles.

The problems in WYSIWYG production for transparency fall in two categories. The first problem is
setting expectations so a designer can make a reasonable prediction of how the document will look when
imaged on a given media. The second problem is the sheer proportions of the computational processes
we are asking of a RIP. PostScript is a three-dimensional language that allows a creator to stack and
prioritize elements on a page. The RIP can literally ‘throw away’ raster data that is knocked out by
graphic elements that completely cover the elements behind. If those elements have to show through the
foreground elements by 20%, the RIP must hold much more raster data in physical memory addresses.
Many times, data is lost if there are not enough addresses available for the computations, and this can
change from one processing of the document to the next.

Designers can employ strategies at each level of document creation to manage these problems. The first
strategy is to use layers well in document creation. By isolating different effects on separate layers, it
becomes easier to isolate and edit the transparent effects when they don’t produce the desired results in
the final output. The layers can be included in a PDF file of the document, and this allows the possibility
of relatively quick editing in PDF editing software closer to the output stage. This can be a completely
different working style for some graphic artists. If we start with the premise that the computer screen
representation of the document is NOT good WYSIWYG and will probably need editing, then we can
justify working with layers more to isolate effects. We can organize design elements on layers after
creation — when we are fine-tuning the effects. Usually, this is a good technique when creating many
elements on several page dimensions. Designers can review their documents and decide if there are
distinct dimensional levels, as page elements are pushed further into the background to pull other page
elements forward. A simple example is a book cover for a retrospective, with pictures from four distinct
decades. The photos and type from each decade can be set on distinct layers, and transparent values of
25%, 50%, 75%, and 100% can be set for each layer. The screen will render one version of the document,
and the printer will render another. It is easier to fine-tune the four layer levels of transparency than to
go back and set new transparency levels for dozens of individual page elements.

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