WHAT ARE KNOCKOUT AND OVERPRINT?
In commercial printing, when elements are set to knockout, the bottom elements are not printed (knocked out) wherever elements overlap. Therefore, when knocked out elements overlap, only the top element will be visible.
Knockout prevents overlapping colours from mixing together, colours appearing muddy or overly saturated.
In commercial printing, overprinting is the opposite of knockout. When elements are set to overprint, they will be printed on top of each other. Where overprinted elements overlap, the colours of the elements underneath will affect, blend with and change the colours of the elements above them.
Overprinting can be used to create new colours and interesting effects, but can also make colours look muddy, oversaturated and or create unexpected results.
Please note that if white is set to overprint, then the elements underneath are not knocked out, therefore the space the white element would normally fill is taken up by the element’s underneath. This results in the white element disappearing from the final printing.
Overprint is commonly used when setting up special effects such as embossing, spot UV and for small or fine 100% black text.
How to Check for Overprint
You can check your artwork in the ‘Overprint Preview’ view of your design program before supplying your artwork. This function will simulate how your artwork will appear once printed.
InDesign Default Black
The InDesign default Black swatch is automatically set to overprint.
Please keep this in mind when creating your artwork using InDesign and ensure that this swatch is only used for small or fine black text.
If the default Black swatch is used for other elements in your design such as shapes, blocks or backgrounds they too will be automatically set to overprint and this may effect your design. We recommend creating a rich black swatch for these types of elements C:50%, M:50%, Y:50%, K100%.
The magenta circle is set to knockout. Because of this, all colours beneath the magenta circle are not printed. This means the colour of the magenta circle is not affected by the colours of the background elements underneath.
The magenta circle is set to overprint. Because of this, the magenta circle is printed directly on top of the background elements. This means the colour of the background elements affects the colour of the magenta circle. When it is turned on unintentionally or by accident, overprinting is a common mistake which can result in the final printed product looking different to what is expected.