P
Need to Know
CMYK
by Eric Miller
he CMYK color model—named after the four base
colors of the model: cyan, magenta, yellow, and
black—dominates the commercial printing world
and in many home-office color printers.
How RGB Leads to CMYK
To understand the CMYK color model, let’s start
with a review of RGB color.
The RGB color model is made up of red, green, and
blue. It is used on your computer monitor and is
what you will view your projects in while it’s still
on the screen. RGB is retained for projects that
are designed to stay on screen (websites, online
documents, and other Web graphics, for example).
These colors, however, can only be viewed with
natural or produced light, such as in the computer
monitor, and not on a printed page. This is where
CMYK comes in.
When two RGB colors are mixed equally they
produce the colors of the CMYK model, which are
known as subtractive primaries.
• Green and blue create cyan.
• Red and blue create magenta.
• Red and green create yellow.
CMYK in the Printing
Process Why Work in RGB and
Convert to CMYK?
The four-color printing process uses four printing
plates; one for cyan, one for magenta, one for yellow,
and one for black. When the colors are combined
on paper (they are actually printed as small dots),
the human eye sees the final composite image. So why wouldn’t you simply work in CMYK while
designing a piece destined for print? You certainly
can, but you will need to rely on those swatches
rather than what you see on the screen because
your monitor is only capable of displaying images
in RGB.
CMYK in Graphic Design Furthermore, some programs including Photoshop
limit what you can do to CMYK images. This barrier
is because the program is designed for photography,
which uses RGB.
Graphic designers must work on screen in RGB,
although their final printed piece will be in CMYK.
Digital files should be converted to CMYK before
sending them to commercial printers unless the
print shop requests something else.
RGB and CMYK colors are close, but not perfectly
identical. Therefore, use swatches when you’re
designing if exact color matching is important. For
example, a company’s logo and branding material
may use a very specific color such a John Deere
Green. It is a very recognizable color and the most
subtle of shifts in it
will be recognizable, even to the
average consumer.
Swatches provide a designer and client with a
printed example of what a color will look like on
paper. A selected swatch color can then be chosen
Black is added to the model because it cannot be in Photoshop (or a similar program) to ensure the
created with the 3 subtractive primaries (when
desired results. Even though the on-screen color
combined they create a dark brown). The K, or
won’t exactly match the swatch, you know what
“key,” stands for black.
your final color will look like.
You can also get a proof (an example of the printed
piece) from a printer before the entire job is run. This
step may delay production, but will ensure exact color
matches.
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Lucid Motif Graphic Industry
Design programs like InDesign and Illustrator (both
Adobe programs as well) default to CMYK because
they are optimized for print designers. For these
reasons, graphic designers often use Photoshop for
photographic elements then import those images
into a dedicated design program for layouts.
Color separation is the process by which
original full-color digital files are separated
into individual color components for four-color
process printing. Every element in the file is
printed in a combination of four colors: cyan,
magenta, yellow, and black, known as CMYK in
the world of commercial printing.
By combining these four ink colors, a wide spectrum
of colors can be produced on the printed page. In
the four-color printing process, each of the four
color separations is applied to a separate printing
plate and placed on one cylinder of a printing press.
As sheets of paper run through the printing press,
each plate transfers an image in one of the four
colors to the paper. The colors—which are applied
as minuscule dots—combine to produce a full-color
image.