2 Spot
Colors + Black = 3 Separations
PostScript
or PDF Color Separations
Two
Degrees of Separation: Composite vs. Pre-Separated
On a printing press each color of ink used in a document is printed
one at a time. Each printing plate used on the press is made up
only of components of the page in that one color.
Separations
are artwork split into component plates of cyan, magenta, yellow,
and black in preparation for process printing (CMYK) or into
the required number of plates for spot color printing - a plate
for each color of ink.
Each separation
prints a single process or spot color. Digital PostScript or
PDF files take two primary forms: composite or pre-separated.
Which you use depends on your software, colors, and the software
or RIP your printer or service bureau uses.
Pre-Separated
A pre-separated PDF or PostScript file contains a separate plate
for each color in the document.
A standard process color job would have four plates (pages) containing
just the color information for each color of CMYK. For spot colors,
you'll have a page for each spot color.
You'll
have separations for each page in your document so a 4 page
CMYK preseparated file would have 16 pages. If you have a preseparated
file you can only print the file as separations and on-screen
viewing is limited to viewing each individual color plate.
Composite
A composite file contains all the color information in one file.
It can be viewed or printed as a composite (everything on one
page). Your service bureau separates the file into its individual
color separations at the RIP.
Choosing
Sides
Which type of file — composite or pre-separated —
does your printer need from you? Ask. That's the best
way to know for sure. Each has its benefits. It's probably obvious
that a composite file will be more compact than a preseparated
file — fewer pages. With composite files both you and
your service bureau can view the document on-screen and check
things like graphics, text flow, etc. more easily.
However,
there are some types of documents that require pre-separated
files for proper handling. At present, composite files don't
contain the necessary information to properly generate separations
for EPS duotones, DCS images, colorized TIFFs, and images with
spot-color-to-spot-color gradients. These will require pre-separated
PostScript or PDF files. Check with your printer if you are
unsure.
Even
when supplying a composite PostScript or PDF to your printer,
you'll want to know how to create and print color separations
to your own printer for proofing purposes. This will help you
see if your composite file will separate correctly (all colors
on the correct plates, no extra colors) and help you catch other
mistakes that might not be apparent looking at the application
file or the composite file.
This
is a brief overview of composite and pre-separated files —
just one aspect of creating color separations. For more in-depth
technical specifications and tutorials as well as advice on
proper preparation of separations in a variety of programs,
see the sidebar resources.
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