Using The Built-In Option To Define The Cmyk Color Space - Adobe PHOTOSHOP 5.0 User Manual

88 CHAPTER 5
Reproducing Color Accurately
Using the Built-in option to
define the CMYK color space
The Built-in option in the CMYK Setup dialog box
lets you specify the ink and separation options.
Photoshop then enters a default value for the dot
gain (the change in the halftone dot size caused by
absorption on the output device). After you print
a proof or talk to your print shop, you might need
to return to the CMYK Setup dialog box to adjust
for dot gain, ink characteristics, and color casts.
(See "About dot gain" on page 93.)
To specify the CMYK settings using the Built-in
option:
Choose File > Color Settings > CMYK Setup.
1
Select Preview to display a preview of your
2
changes. A flashing bar under the option indicates
a preview is being created.
For CMYK Model, choose Built-in.
3
4 For Ink Colors, select an ink type.
The default color values used in the color
separation calculations are designed to produce
quality separations using SWOP (Specifications
for Web Offset Publication) inks on coated paper.
These inks differ slightly from those used in
Europe. Similarly, the color and ink absorption
qualities of the paper stock affect the final printed
result. You can think of this information as telling
Photoshop what printed cyan, magenta, yellow,
and black look like given a certain set of inks and
paper stock under your lighting conditions.
Note: In most cases, printing ink characteristics do
not vary greatly from printer to printer within the
same printer type. For example, one Tektronix
Phaser II printer prints ink hues very similar to
another one. But the amount of dot gain can vary
significantly. Thus, for a different printer of the same
type, you may have to change the dot gain setting in
the CMYK Setup dialog box but not the printing
ink colors.
If you choose Custom for Ink Colors, the Ink
Colors dialog box appears. (See "Setting the
characteristics of custom ink colors" on page 96.)
Verify the dot gain percentage.
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Do not adjust this value until you have run a proof
(which includes a calibration bar) and have
measured the density values on the proof with a
reflective densitometer. Change this value if your
print shop has provided a different value for
estimated dot gain. See "Calibrating the screen
image to the proof " on page 92 and "Specifying
dot gain" on page 94 for more information on
dot gain.
6 Click OK.
For information on choosing separation options,
see "Adjusting separation options" on page 89.