What is overprint in design and printing
Overprint is a technique used to conceal registration errors or achieve new color combinations. In this method, two objects can combine or cover each other's color in their overlapping areas. It's important to note that the resulting color in the overlapping area is automatic and cannot be defined numerically by the graphic designer.
By default, graphic software and RIPs in lithography tend to avoid overprinting to leave the underlying area of each object blank. This blank space optimizes ink consumption in higher print runs. However, when a registration error occurs, this blank area can become visible, causing a printing defect.
Overprinting eliminates the default blank area under each object. This process can prevent the visibility of underlying white in case of registration errors but increases ink consumption due to the overprinting and color mixing process. However, this increased consumption is justified by eliminating the error. There are specific cases where overprinting should not be used, and understanding the reasons is crucial.
Overprint and Black
One of the most important applications of overprinting is when solid black text (K=100%) is placed on a colored background. By enabling this feature, the white under the text is covered, and even if a registration error occurs, there will be no double vision or white edges. Black ink has a specific density and thickness, so no background color, regardless of its type, can cause the black text to fade or become tinted. especially in small-point texts, Overprinting should always be used in such cases.
In vector software like Illustrator, InDesign, and CorelDRAW, the Fill Overprint option is used to define overprinting. In raster software like Photoshop, this option is called Blending mode and is typically set to Multiply (although Darken is more suitable).
Remember that...
It's recommended to avoid using Photoshop for overprinting for two reasons: first, the text output from this software is of lower quality compared to vector software; and second, some RIPs consider blending options as a technical error during preflight and may cause errors in halftoning.
