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Four-color process printing is an amazing procedure. Few
people outside of the printing industry fully realize either the complexity or
the different processes available for converting a color photograph for use in
a printed medium. Successful four-color process printing requires a thorough
understanding of the nature of light, color theory, the composition and function
of different inks, and the way our brain perceives color.
In four-color process printing, inks are used together to
create new colors. Because process inks act much in the same way as filters,
subjects containing several different colors or gradations of colors can be
reproduced using just three colors of ink: yellow, magenta (bluish-red), and
cyan (blue-green). Process yellow absorbs only blue light, magenta absorbs only
green light, and cyan absorbs only red light. When yellow is printed on top of magenta,
the result is a shade of red. Yellow printed on top of cyan results in a shade
of green. In theory, when yellow, megenta, and cyan are printed on top of one
another, black should be the result. In reality the result is a brownish color,
due to the nature of pigments. To help compensate for this, black is added as
the fourth color in four-color process printing. Black also creates added depth
and definition to the reproduction.
insert color photo that we printed here
Look at the photograph above, you can differentiate hundreds
of different colors. However, we printed it using only four inks. The PrePress
Computer System evaluates the colors in the original photo and electronicaly
determines how much yellow, magenta, cyan, and black it would take to
approximate each color in the photograph. Producing a four-color separation,
one for each different printing ink that was used. Eventually, through a
complex series of procedures, printing plates were produced from this
four-color separation. These plates were the image carriers used on the
printing press that enabled the press to transfer ink to paper (thus the term
offset printing).
This transfer resulted in an image consisting of hundreds of
thousands of different-sized dots, just like in a black-and-white halftone,
except that now instead of just one black-and-white halftone, there were four
colors of ink laid on top of one another. If you look at the photograph through
a magnifying glass, you can see some of the dots are printed on top of one another,
some printed right next to each other, and some are just close together. The
viewer's mind is constantly blending the dots approximating the colors found in
the original subject.
Why Four-Color Process Printing? (CMYK) ...
Unlike inkjet printers or color photocopiers, full color
(C-M- Y-K) printing provides accurate, detailed, brilliant reproduction of
your originals. Look at any magazine cover - Time, People, National Geographic
- for an example of 4-color process printing. This is the kind of printing
found at "commercial printers", not your local quick-printer shop.
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