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This article is published as part of the exclusive AG blog series Avoiding 10 Illustrator Publishing Pitfalls

Overprint black title

Overprinting black text and other objects can ensure quality print jobs. It's often the simplest way to ensure crisp results and is a age-old work-around for the issue of mis-registration on a print press – a topic discussed in the previous article, Rich black strokes and text. Here, we'll describe methods to set objects defined with black ink only ("pure black") to overprint using both native methods and tools as well as the overprint black option found within Phantasm CS.

If an object isn't overprinted, what is it?

By default, objects are created without Overprint, which is a setting found in the Window » Attributes panel. Therefore they will "knockout" all objects beneath them. To illustrate this, below are two copies of the same simple artwork where a black circle is placed above a rectangle colored using tints of Cyan, Magenta and Yellow:

Knockout and Overprint print example

The left-hand artwork shows the default attribute of no overprint being set on the black circle. Looking at the representation of the CMYK separations beneath, it may be seen that a section of the underlying square contains no color where the overlying black circle was placed (the dotted arc highlights the cut-away section).

The right-hand example illustrates what happens when the black circle had Overprint Fill ticked in the Attributes panel. Set this way, the underlying objects are not affected by the circle placed on top.

By overprinting objects, as opposed to knocking them out, any mis-registration on the print press will not result in a halo effect around black objects where the underlying separations have shifted relatively. This has been simulated below:

Mis-registration simulated

Manual solution

Note: with this method and ones to follow, it's only possible to select objects in accessible layers. Objects in locked layers will remain unaffected and therefore can't be immediately corrected. It is suggested that all layers are first unlocked via the Layers panel before using these techniques.

If you wish to ensure that all 100% Black-ink-only strokes are set to overprint, simply select an object (or temporarily create one) which features a stroke of this color and then opt for Select » Same » Stroke Color. Then via the Attributes panel (choose Window » Attributes if not already open), click on the Overprint Stroke tick box.

Mixed overprint attribute
Note: if you ended up with a selection of strokes, some with overprint set and others not, the Overprint Stroke option will appear as shown left. Simply click on this "dash" mark to make all attributes set or unset.

This method is quick and simple, may be used for strokes and/or fills of varying tints, and can also be incorporated into an Illustrator Action. However, it doesn't allow for selection of a range of pure black tints. The selection method will only pick strokes and/or fills of exactly the same color as the original one selected.

Illustrator's own Overprint Black tool

There is a hidden gem in Illustrator called, appropriately, "Overprint Black". This tool receives no publicity and yet has a very specific and important use just for this situation. It may be found in Illustrator CS2 under Filter » Colors » Overprint Black… or for Illustrator CS3 and above under Edit » Edit Colors » Overprint Black….

Overprint Black native Illustrator tool

The Illustrator user manual details its operation, so we won't re-cover it here. But it's interesting to note that it allows objects that aren't just pure black to be set to overprint, so long as the black component matches the tint level specified in the tool.

The only negative side is that this tool doesn't allow a range of black tints to be adjusted in one go. It's often just as valuable to set especially darker tints of black to overprint.

Overprint Black print option

A third native method in Illustrator is to set all blacks to overprint via the Print dialogue window. Note that this option only becomes available when printing to a PostScript printer, Acrobat Distiller or similar – ie. not a typical desktop printer. And then it will only be allowed when Output | Mode: is set to In-RIP Separations as may be seen below:

Overprint black print option

This is a bit of a blunt instrument and should be used with caution. Not all artwork would improve if a blanket overprint black setting is defined.

Overprint Pure Black option within Phantasm CS

An alternative method presents itself in the Phantasm CS range. The technique described here is very similar to the white overprint fix found in the Banish overprint white article plus the later Rich black strokes and text article. Once again, the advanced options are called into action and applies to all Phantasm CS editions.

As with the techniques used in the afore-mentioned articles, it's advised that the Phantasm CS Filter "Shift to Color" is used for the same reason; a 0% shift ensures no actual color change takes place while simultaneously allowing the advanced options to come into play. The tool's Filter version is used rather than a live Effect as a permanent change is required.

Procedure:

Step 1
Select the artwork you wish to convert all occurrences of pure black to overprint. Note that this only works on objects which have a tint of black applied and no other ink levels. All object types may be adjusted, but it's possible to target specific attributes only: Fill, Stroke, Bitmap (ie. all images) and – in Phantasm CS Publisher only – Text. This could be all the artwork in the document by opting for Select » All.

Step 2
Open the Shift to Color tool by opting for Filter » Phantasm CS » Shift to Color… in Illustrator CS3 or earlier, or Object » Filters » Phantasm CS » Shift to Color… in Illustrator CS4 or above.

Step 3
If not already open, display Phantasm CS' color adjustments advanced options using the entry in the window's pull-down menu as shown below:

Show advanced options

Step 4
Phantasm CS offers the tick option Overprint Pure Black as shown below:

Phantasm CS Overprint Pure Black option

Differentiating this method from Illustrator's own Overprint Black tool, the associated slider ranges from 1-100% where the percentage dictates of level of black tint or above that should be considered for overprinting. Therefore a level of 1% would ensure that all occurrences of pure black, regardless of the tint level, would be set to overprint.

The associated setting is the Text Only tick box. This ensures that only editable pure black text – not outlined text – would be set to overprint.

Finally, click OK to apply the changes.

Automating the process with Phantasm CS

As with all Phantasm CS Filters, they may be incorporated into an Illustrator Action. Simply start recording a new Action where the act of setting pure black to overprint as described above takes place. Replaying this will replicate the process instantly.

It's not possible to fully describe the process of creating Illustrator Actions in this article. Therefore it's recommended that for further information you view tutorials found across the internet or start with Adobe's (admittedly slightly outdated, but still relevant) own page on the subject.

Visually checking overprinted objects

On a related note, Phantasm CS Studio and Publisher provides a very useful visual checking system to see which objects are being set to overprint. First ensuring that you have the Overprint Preview rendering mode enabled (View » Overprint Preview, if not already done do), opt for Phantasm CS' own View » Output Preview » Overprint Preview. This tool gives a very quick visual overview, highlighting all objects set to overprint as may be seen in the example below:

Phantasm CS Overprint Object Preview tool

 

Thanks for www.keepdesigning.com for the free vector graphics used in the background of this article's title image!

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