Document Trapping Flashcards
(30 cards)
Amount of ink printing on top of another ink
Ink trapping
What is trapping
2 kinds: object & ink trapping
Vector and raster objects that overlap
Object trapping
The four trapping instances
- Overprint
- Knock out
- Keep back
- Spread or choke
Transparent colour are also known as
Process colours
Overprint occurs when…?
One colour prints on top of another colour
Overprinting is used because
Overprinting is used to create different colours
E.g. Printing yellow over magenta = red
Black almost always overprints other colours (especially when dealing with small black type): T or F
True
Does black overprint when an opaque ink is being printed overtop black?
No, an opaque ink is the exception to the rule that black overprints other colours
How to prevent overprint on large black type?
Treat large black text as an object
Knock out is when:
- An object removes all the image below it creating only that object printing in that space.
- Only occurs when using 1 colour
(E.g. If yellow must stay yellow, we must remove magenta from behind it)
Opposite of overprinting is:
Knock out
Keep back is
Knocking out the chromatic (non-black) inks around reverse text and images and edges in rich black situations
Spread occurs when
The expansion of a lighter colour into a darker colour to compensate for press misregistration
What makes slight misregistration less noticeable?
Slight overlap
Choke occurs when
Lighter colours contracts into darker colour b/c of press misregistration
What involves distorting the shape of an object? (I.e. Making it fatter or thinner)
Spreads & Chokes
To minimize the negative affect of distortion, always…?
Distort the lighter colour
Lightness is defined by…?
Neutral density (value as it would appear as a greyscale measured with densitometer) using visual filter
What is a visual filter?
Filter for K
When not to trap
- Seperate colours - colours don’t touch one another
2. Common colours - foreground & background objects share one or more colours
Trap inks not colours : T or F
TRUE
What part of raster images need trapping
Often the outside edges only need trapping
Images commonly too complex to trap and really don’t need trapping are also known as…?
Raster images