Trapping: The Invisible Border of Colors
In previous articles, many points were discussed regarding color and overprint. However, this technique is mostly effective for black. Now, the question arises: how should we handle other colors? To conceal registration errors, should we still execute with the overprint command, or can another solution be offered? It is here that another color adjustment technique becomes apparent, which will be explained in the following.
We begin the examination of this new topic with this definition: If we intend to treat colors using the overprint method and apply it to all errors and color combinations, the color of the object will be completely transformed. For example, if we overprint a blue text object on a yellow background, the result will certainly be a green text. However, the green codes are not user-definable, and a specific green is created. Although overprinting eliminates the white space beneath the text and conceals registration errors, our desired outcome is different.
Trapping is a crucial technique in the prepress stage used to prevent color misalignments during printing. This method, through a slight overlap between adjacent colors, prevents the creation of unwanted white lines or gaps resulting from registration errors.
Solutions for Printing
Understanding the issue of overprinting for color and utilizing trapping stems from knowing your needs. Therefore, be sure to review the color combinations in the overprint article and understand that overprinting causes color changes and is not always effective. Registration errors also occur to some extent and are sometimes imperceptible to the naked eye, but the application of trapping or overprinting is effective in preventing errors.
In the world of printing, we draw a thin line, similar to the example above, between any two color objects. The border of two objects is indicated by a line with a defined thickness, which can start from 0.2 millimeters. The exact amount changes according to the need and can extend up to 0.5 millimeters. However, this border is shared between both objects, and only that line is overprinted, while the colors of both objects are preserved.
We do not intend to examine the conditions of trapping in various situations at this initial stage and complicate your understanding. This is because, with practice, repetition, and reviewing different files, the matter will gradually become completely clear, transforming you into a professional. However, there are generally two basic rules for trapping:
1. The lighter object expands.
2. The size of the objects should not change significantly after trapping is applied.
Now, let's examine the previous image again. Precisely here, trapping moves towards the blue color. This means that the lighter area, which is yellow, should become larger according to one of the two main rules. The second rule is also observed, meaning that the size of the text object on which trapping has been performed has not changed significantly.
Registration Check
After applying the trapping command, you can simulate the result relative to printing. Do not forget that the stroke is defined as overprint, and the border between two objects in this state is called trapping. However, registration error is still occurring but is hidden behind the trapping. We can examine this error in a state without trapping or with its use and simulate the registration error using the ESKO Deskpack plugin. In the figure below, the registration problem occurred but is not visible.
Conclusion
Considering the specialized nature of topics such as trapping, color profiles, and color management, one cannot certainly become a professional through a single article and the display of a few images. However, understanding the subject can be your guiding light on this path. Trapping not only covers your registration errors but can also greatly assist the printing operator in controlling speed and proceeding with printing with fewer errors during production.
In previous articles, we stated that it is not always necessary for black ink to be overprinted because the ink consumption increases. The same process can be applied with trapping. This technique helps conserve ink consumption and reduce errors, and the calculation of a product's production at the end of the year will be done optimally with lower costs. Although the trapping technique requires a significant amount of time, it is still one way to reduce costs.
