2013

Imagesetting 299
To change the screen angle and
frequency, click on the ink name
to select it then click
PROPERTIES.
This opens the
SEPARATION
PROPERTIES
dialog:
Angle: To change the screen angle for this color, type in a new value in degrees.
Frequency: To change the screen frequency for this color, type in a new value. This
overrides the default screen frequency (described in PostScript options earlier) for
this color.
Print this ink: This duplicates the check box in the main
SEPARATIONS dialog.
Overprint this ink: This duplicates the check box in the main
SEPARATIONS dialog. It
protects the selected color from being knocked-out, so works in the reverse to object-
level overprinting. Overprinting is described later in the chapter.
Print spot colors as process colors: Desktop printers and some printing processes
can only print process (CMYK) colors. Select this option to print any spot colors as
their equivalent CMYK color. Note: some spot colors look very different when output
as CMYK, and it removes the ability to use PANTONE COLOR BRIDGE colors or any
special inks. The main use of this option is when checking your artwork on a local
printer.
Overprinting
If you are producing color documents that will be printed on litho printing presses,
you may find overprint useful. Printing presses are mechanical devices with the
inevitable slight misalignments when they are running. Overprinting lets you
overcome these misalignments. For example, your job may have a black circle on a
cyan background. When the document is imageset, the circle appears on the black
separation and the cyan separation has a non-printing area under the circle (the
technical term is that the circle "knocks-out" the background). The knock-out is the
same size as the circle.
A black circle knocks-out out the cyan background