Specifying Color

9

Image Captur

e

8

Uses of Different Color Models

Color Conversion

Inkjet

Hi-res inkjet

Digital press

Offset press

6-Color offset press

Screen printing

CMYK gamut

RGB gamut

CMYK

RGB

PMS 659

CMYK

Cross section of a CIE Color Model

The major challenge of
image reproduction is the
varied “

gamuts

” of each

color system. Some col-
ors can be displayed in
RGB, or created with spot
color inks that simply can-
not be reproduced with
the CMYK ink set. The
challenge is to alter the
range of colors in the
original file to colors
that can be printed with
CMYK. The alternative is
to add spot colors, or to
move to a “

high fidelity

”

color model using six or
more inks.

The range of available options
for image capture is constantly
expanding. Scanners and digital

cameras get better and cheaper all the
time. Today’s professionals can decide
whether to buy a scanner that’s accept-
able for their needs, or to continue to
buy scanning services outside.

Drum

scanners

are still widely used for the

most demanding color printing, but

flatbed scanners

now offer sufficiently

high quality for most publications.

With digital cameras and digital stock
photography you bypass the need for
scanning altogether. Digital images are
ready for use in publications.

For print applications, digital image
quality is difficult to determine precisely.
The main issue is not resolution — most
scanners and cameras capture enough
data for publishing uses. The real mea-
sure is

dynamic range

— the ability of

the device to record detail in both the
shadow and highlight areas of an image.
The best scanners and cameras have a
broad dynamic range, but the range is
not always reproducible in the final pub-
lication. An image produced as a color
transparency will contain a much
broader dynamic range than that same
image reproduced using ink on paper.
In most cases, however, much of the
image detail is lost in the scanning pro-
cess, so the more detail you start with,
the greater your ultimate flexibility.

In the end, image quality is mainly in
the eye of the beholder. Educated and
experienced clients demand the most
exacting image quality, but many pub-
lishers are willing to accept color repro-
duction that they feel is “pleasing,”
rather than perfect. Again, clearly estab-
lishing expectations at the outset will
lead to a successful product and a satis-
fied client.

After an image is digitized, it
still must be converted into a
format ready for publication.

Desktop scanners and digital cameras
capture data in

RGB

(Red, Green, Blue)

format, but most printers and presses
use

CMYK

(Cyan, Magenta, Yellow,

Black) inks and toners for output. These
are known as

process

colors. RGB files

must be corrected for color and tone
balance, and then converted to the
CMYK format for printing. This con-
version requires skill and experience;
there’s nothing automatic about it. The
optimal blend of inks varies widely, de-
termined by the press you’re using, the
substrate, and a host of other factors.
Many designers rely on default settings
for this conversion, but the results are
always inferior to those achieved by an
experienced technician working with
software like Adobe Photoshop™ or
Corel PHOTO-PAINT

®

. If you’re not

adept at image correction and color con-
version, speak to your service provider.

CMYK inks can be combined to create
most printing colors, but sometimes a
very specific color is required.

Spot

color systems

, such as the Pantone

®

Matching System (

PMS

) or the

Toyo

system, offer solid ink colors from swatch
books. These inks are particularly useful
in 2- and 3-color print jobs, in 6- and
7-color

HiFi Color

materials, or for an

exact match on a corporate or product
color scheme.

Most of the Pantone and Toyo colors
can be closely simulated with CMYK
inks, but not all of them. Proofing these
inks can also be a challenge, particularly
on digital printers, which usually use
CMYK pigments. It’s inadvisable to de-
sign with these colors unless you intend
to use the actual inks.

TruMatch™

and

Focoltone™

generate color swatches

comprised of CMYK inks, and offer a
good alternative to the spot color systems.

RGB

Spot Color

CMYK

Monitor

Projector

Film recorder

All image sensors capture data in RGB format (Red, Green,
Blue), and all monitors, projectors and film recorders
process or display RGB data. RGB is an additive color
model — all the colors combined create white.

In the publishing world there are three color models worth understanding:
RGB, CMYK and spot color. Each has its use; most publishers use all three.

Rather than projecting light, printing

reflects light off the

page, and so a different color system is required. Four-
color printing uses a subtractive color model with CMYK
(Cyan, Magenta, Yellow, Black) inks.

Rather than combining CMYK inks to simulate colors, spot
color printing uses inks of single colors for exact color
reproduction. Most publishers use the Pantone Matching
System (PMS) for spot color.

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Digital Photography

Scanning

Stock Photography

Digital cameras have a broad
range of price/performance
features, from low-end con-
sumer cameras to professional
studio models. The flexibility
and convenience of digital
photography is outstanding,
but the image quality is not
always high enough for some
print applications. Digital cam-
eras capture images in RGB
format, so publishers must
color-correct their pictures and
convert them to CMYK data
for printing. These devices, on
the other hand, are ideal for
Web-based publishing use.

With prices starting below
$100, color desktop scanners
are within reach of all de-
signers and publishers. Better
quality flatbed scanners han-
dle larger artwork, and can
scan both reflective and trans-
parent originals. Service pro-
viders continue to offer high-
end flatbed and drum scan-
ning services that are suited
to more demanding or higher
volume applications. Service
providers can also provide
scans that are color-corrected
and converted to CMYK for-
mat, ready for printing.

Digital stock photography ser-
vices are expanding rapidly,
offering a nearly limitless
range of original images,
ready for publication. Images
can be purchased on CD-
ROM, or often downloaded
directly from the World Wide
Web. Buyers need to check
carefully that stock images
have been professionally
scanned and are in a format
ready to be printed.