System information

Object in Separation BlackObject in spot color black, Gray or 100 % KInk
0 %Yellow
100 %100 %Black
• Be careful with color conversions, because the overprint behavior may be unpredictable. If you
do color conversions, proofing is an absolute necessity. You can proof your PDF documents by
printing them on a composite output device, or on screen using the Overprint Preview and
Separation Preview features of Adobe Acrobat.
Overprint modes and object types
A PDF file may contain different types of objects, such as text, line art and images. Some object
types have an overprint behavior which depends on the overprint mode, others don’t. We can
distinguish the following:
Overprint-mode-independent object typesOverprint-mode-dependent object types
CMYK imagesCMYK text
CMYK shadingsCMYK line art
CMYK image masks
In other words, overprint modes only have an effect on CMYK text, line art and image masks.
There are two “overprint modes”:
• Standard overprint mode, also known as “OPM 0”
• Illustrator overprint mode, also known as “OPM 1” or “nonzero overprint mode”
The difference between both modes lies in the effect of the tint value 0 for one of the CMYK inks:
• In standard overprint mode (OPM 0), the tint value 0 of one of the CMYK inks in the foreground
object has a knockout effect on the color rendering of the underlying object. In other words, a
foreground ink with a C, M, Y or K value of 0 % erases the corresponding background ink. Here,
the “foreground inks win” principle applies.
• In Illustrator overprint mode (OPM 1), the tint value 0 is neutral: it is ignored (as if it were “not
specified”) and has therefore no effect on the color rendering of the underlying object.
Example
Given two overlapping colored circles with the following fill colors:
Circle in the foregroundCircle in the backgroundInk
0 %40 %Cyan
0 %0 %Magenta
60 %0 %Yellow
0 %0 %Black
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