There are two basic models used in
DTP (Desk Top Publishing) software for specifying
color. They are called spot color and process color.
Spot color is a way of specifying that one or more
pre-mixed ink colors be used on a printed piece.
Each spot color is a different ink on the press.
Process color is a special process used to create a
wide variety of colors with only four standard inks:
cyan, magenta, yellow, and black (commonly called
CMYK.) Not all colors can be reproduced using
process colors. Many colors such as metallic colors
have no process equivalent. This is why spot colors
are often added to a design even when the job
requires four color process inks for color photos.
The process and spot color models arise from the two
basic methods of creating colors on a printing
press. When a press operator is preparing the press
for a press run, he or she loads the rollers on the
press with ink. Each roller assembly is loaded with
a different color. As each piece of paper is fed
through the press, it passes through each of the
roller assemblies and is imprinted with each color
in succession. Usually, one of the inks is black.
Often, one or more spot colors are
added to enhance the design. If a color photo is
used, then four of the roller assemblies are loaded
with the colors cyan, magenta, yellow, and black.
These four process ink colors are printed on top of
each other in varying amounts to create all the
possible process colors. Printing inks are typically
semi-transparent so that overlaying colors result in
a third color. For example, cyan and yellow will
produce green, magenta and yellow produce red. By
using spot color inks and the four basic process
component inks, a press operator can reproduce
designs that range from simple black only jobs to
full color reproductions. Understanding how colors
are put down by the presses is important for
understanding how color works in your designs and
how to correctly specify colors, whether spot or
process, in your DTP software.
Spot Colors
Spot colors are simply colored inks.
The range of ink colors available and means for
specifying these inks depends on the color system
used by your printer. Printing Services uses the
Pantone color system. There are over a thousand
colors available in the Pantone color system. Each
color is specified with a label which usually takes
the form:
PANTONE xxxx CVC
The xxxx is usually a number in the hundreds but can
be in the thousands. A Pantone color can also have a
label like PANTONE Reflex Blue CVC. All designers
should definitely have a current version of a
PANTONE MATCHING SYSTEM color guide. These are the
best way to see what the ink you choose is going to
look like once it is printed; choosing the color by
its appearance on your computer screen is unreliable
and inaccurate.
Process Colors
Unlike Spot colors, which use a
different pre-mixed ink for each printed color,
Process color is a system of using four standard
inks and mixing them on the press to create a wide
spectrum of different colors. The inks used are
Cyan, Magenta, Yellow, and Black (CMYK.) One of the
most common uses for process color is for color
photograph reproduction. The color images are broken
down by software into their CMYK components, and
each component layer is imaged to a separate piece
of film. When the CMYK plates are printed on top of
each other, the color photo reappears in full color.
Pantone colors can also be built out of process
colors. For example, your job may call for four
color process and one spot color. It may turn out
that the spot color is easily reproducible with
process colors. You could save some money if you
designed your piece using four color process builds
for everything instead of adding a fifth color.
Please discuss these issues with a CSR and decide on
your color scheme before you spend a lot of time
creating the electronic files.
Their are several limitations on what can be
simulated with process colors. Many Pantone colors
are simply not reproducible with process colors.
Since process colors use Cyan, Magenta, Yellow, and
Black to create the other colors, you can imagine
you would have more success simulating colors that
are close to one of these colors to start with. Cyan
and Magenta make a dark purple, Magenta and Yellow
make a red, Cyan and Yellow make a green. But these
builds tend to be very dark, and a little dull.
Confusing Spot and Process
Colors
Since each spot color results in a
different piece of film when the job is sent to the
image setter, it is critical that the colors be
specified correctly in all your software packages
and graphics. One common mistake is to confuse spot
color definitions and process color definitions. You
have to explicitly tell the software one way or the
other. People often just go into the color
definition window and make a new color without
considering whether it is a spot or process, and the
result is the color is set to whatever the default
for the software was. Your odds are not good for
ending up with the correct default; less than 50:50
since there are often more choices available.
Tints
Besides specifying a spot or process
color, you can also make an object's line or fill a
tint of some other color, either spot or process.
Tints are expressed in percentages from 0 to 100. A
50% tint of PANTONE 128 CVC will produce a 50%
halftone screen for that ink in the specified areas.
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