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How transparency
and flattening affect workflow and print output
Flattening alters a file with transparency to enable
prepress workflows, which may visibly reduce output quality.
If the output is not what is expected, you can often correct
the situation if the original files are available.
Transparency is no longer “live” and editable:
Although the result still looks transparent, the formerly
transparent objects in flattened designs are opaque, and they
won’t be transparent to other objects in other applications
(that is, the transparency is no longer “live”
to other objects). In addition, some of the original objects
may be transformed into less editable formats. (For example,
vectors can become rasterized and type can become outlines
or be rasterized through flattening.)
Adjusting transparency attributes and objects after flattening
requires making changes to the original file, and then exporting
or printing (flattening) it as a new file.
Rasterization may cause visible changes:
The flattener’s need to convert vectors to rasterized
areas (or type to outlines) can sometimes produce undesirable
visual results, such as jaggies (resolution mismatching between
objects), color stitching, or thickened stroke widths.
These results can occur if the flattener rasterizes only a
portion of a large, complex design. What the flattener rasterizes
is based on the types of objects being flattened (type, gradients,
spot colors, and so on), on the file’s complexity, and
on the flattener settings that are in effect when you save-as,
export or print.
Resolution may not match the device:
Sometimes rasterization is needed as part of flattening. The
resolution used for rasterization must be user-defined because
the device resolution is not automatically available at the
time of flattening. Also, the device resolution may be inappropriately
high and may result in huge spool files and significant flattening
time without a noticeable improvement in quality.
Objects that remain in vector format remain device independent
and will scale correctly to match the resolution of the output
device. Fonts may not match: Since flattening on your computer
uses your computer's fonts, not the RIP or printer's fonts,
there may be a mismatch between fonts within the flattened
region & fonts processed at the RIP.
Colors may change:
The use of transparency can change colors in several ways.
First, certain blending modes, such as Multiply can result
in generating ink on all process plates, even on those not
originally specified.
Be sure to use the Overprint Preview mode for previewing the
appearance of spots and overprint.
Second, if ICC color management is used in the workflow, colors
involved in transparency may be transformed earlier than expected
and may not match the actual press conditions after being
flattened.
In applications like Illustrator 10.x, this transformation
can happen if you haven’t carefully chosen the working
space profile for the document.
In InDesign 2.x—which supports working in multiple color
spaces—the Transparency Blending Space profile must be
chosen with the same care. |
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