Adjusting Separation Options - Adobe PHOTOSHOP 5.0 User Manual

To save and load settings:
Use the Save and Load buttons in the CMYK Setup
dialog box to save these settings as an ICC profile.
The profile can then be used again by Photoshop
and other ICC-aware applications.

Adjusting separation options

Along with the other options when you choose
Built-in as the CMYK model in the CMYK Setup
dialog box, the separation options control how the
CMYK plates are generated. The separation
options determine the method used for black
generation and undercolor removal and specify
the total ink limit for the press.
When converting RGB values to CMYK,
Photoshop uses information in the RGB Setup and
CMYK Setup dialog boxes. The settings in these
dialog boxes help ensure the closest match possible
between the colors on-screen and in the final
output. The CMYK Setup dialog box settings
determine the precise CMYK values chosen for a
given RGB color. Once an image is in CMYK
mode, Photoshop converts the CMYK color values
internally to display them on an RGB monitor.
(See "Converting to CMYK" on page 97.)
About separation types and black
generation
To make color separations, the three additive
colors (red, green, and blue) are translated into
their subtractive counterparts (cyan, magenta,
and yellow). In theory, equal parts of cyan,
magenta, and yellow combine to subtract all
light reflected from the paper and create black.
Due to impurities present in all printing inks,
however, a mix of these colors instead yields a
muddy brown. To compensate for this deficiency
in the color separation process, printers remove
some cyan, magenta, and yellow in areas where
the three colors exist in equal amounts, and they
add black ink.
A given color can be translated from RGB mode to
CMYK mode in an endless number of ways. But
prepress operators typically use one of two ways to
generate black in print: undercolor removal
(UCR) or gray component replacement (GCR):
With UCR, black ink is used to replace cyan,
•
magenta, and yellow ink in neutral areas only (that
is, areas with equal amounts of cyan, magenta, and
yellow). This results in less ink and greater depth
in shadows. Because it uses less ink, UCR is
generally used for newsprint and uncoated stock.
With GCR, black ink is used to replace portions
•
of cyan, magenta, and yellow ink in colored areas
as well as in neutral areas. GCR separations tend to
reproduce dark, saturated colors somewhat better
than UCR separations do and maintain gray
balance better on press.
Choose the type of separation based on your paper
stock and the requirements of your print shop.
ADOBE PHOTOSHOP 5.0 89
User Guide