In-RIP Trapping

Finally! A trapping solution that lets you apply complex trapping commands to PS, EPS and PDF files automatically at the RIP. Adobe In-RIP Trapping for Symphony gives you the options and controls you need to quickly apply and edit trap preferences for the way you want to run on press. This saves your prepress department hours of unproductive time applying traps manually from within applications that offer limited trap options and mixed results. Below is a brief description of what trapping is and how Adobe In-RIP Trapping turns a difficult prepress task into a huge time saver.

What is Trapping?

As all printers know, it is difficult to achieve and maintain perfect registration in a job. In jobs where colors do not touch one another, a certain amount of misregistration will go unnoticed. In jobs where colors do touch each other, misregistration can cause visible and unsightly gaps. In jobs where colors touch one another, trapping is often used to make misregistration less visible. Trapping involves creating a region of overlap between two adjacent colors, so that even if the colors are out of register, no gap is visible.

In the illustration below you can see how trapping helps this problem.

Figure 1 Figure 2 Figure 3 Figure 4
Figure 1: An Image that is in register, with no trap applied. Figure 2: An image that is out of register, with no trap applied. Figure 3: An image that is in register with trapping applied. Figure 4: An image out of register with trapping applied.


Application Trapping vs. In-RIP Trapping

Many graphics applications offer a variety of methods of performing trapping. Applications may also offer an option to automatically perform trapping, either on selected objects or on the entire document, as it is printed. Both of these methods of trapping can be very effective, although virtually all graphics applications are limited to trapping native elements (elements which were generated within the application). They cannot trap placed elements, and they often cannot trap native elements to placed elements in an intelligent manner.

In-RIP Trapping is not limited in what it can trap: any element(s) on a page, regardless of their origin, can be trapped with other elements. This is mainly because In-RIP Trapping’s trapping decisions are made on the basis of ink characteristics. In general, lighter colors are trapped to darker colors. The characteristic used to measure “lightness” is Neutral Density. For that reason, In-RIP Trapping is a more generalized trapping solution than application-based trapping.

The following trapping options are available in the Trapping section of the Ticket Editor, of Symphony and can be edited on a file per file basis for best press results.

Trap Width, Default: The width of a trap, for abutting colors should be equal to the maximum amount you expect a job to be out of register. A value which is too small can allow white space between adjacent colors if the job is misregistered, while a value which is too large will be more visible than necessary. Typical values for offset printing under ideal conditions are about .25 point.

Trap Width, Black Width: The width of a trap, when one of the colors is black. Also, this value determines the stayaway amount when colors and black overlap one another, as in a rich black. Larger values here are less visible than in Trap Width, Default, above.

Step Limit: The amount which components of abutting colors must differ in order for trapping to take place. Lower values will tend to cause more trapping, while higher values will cause less trapping. The default value is 10%, and best results can be had between 8% and 20%.

Black Density: The density above which a spot color is treated as black. Change this value to be equal or less than the density of a dark ink if you want the ink to be trapped using the Black Width setting.

Sliding Trap: Moves the trap from the darker side of an edge to the centerline. Values between 0% and 100% are acceptable, depending on the characteristics of the job. The default value is 70%.

Black Color: The minimum percentage of black ink for which the Black Width setting is applied. Settings of 70% or higher are recommended.

Color Scaling: Determines the darkness of the trap region. At 100%, the colors which overlap one another in the trap region are not reduced at all; at 0%, the neutral density of the trap region is equal to the neutral density of the darker color.

Trap images to objects: When selected, trapping is allowed between raster images such as TIFF files placed in a document, and vector elements such as drawn objects and text. The way in which the two types of elements are trapped to one another depends on the setting in the Image Trap Placement pulldown menu:

Center: Trapping occurs along the centerline between images and objects.

Choke: The trapping is pushed all the way into the image.

Normal: The trapping between images and objects follows the same rules used for trapping between objects. If the contents of the image vary considerably, it can cause “jumping traps” which shift back and forth between the image and the object.

Spread: The trapping is pushed all the way into the object.


Figures 5 thru 9 illustrate trapping between images and objects.

Figure 5: No Trapping.

Figure 6: Center Trap, this is seldom appropriate for text.

Figure 7: Choke (text), spread for (images)*, this setting works best when text is lighter than image, overall.

Figure 8: Normal Trap, this setting works well when the image is relatively consistent, but can cause “bouncing traps” if image varies considerably.

Figure 9: Spread(text), Choke (images)*, this setting works best when text is darker than the image, overall.

A NOTE on Terminology: The terms Choke and Spread, in this context, assume that the object surrounds the image. In the case of text which sits on top of an image, it is the image which surrounds the text, and thus the terminology is backward; Choke spreads, and Spread chokes.

Internal Image Trapping: Enables trapping within an image. This setting can be useful for high contrast images such as logos and maps, but should not be used for most continuous tone images. This option can significantly increase RIP times when used with large, high-resolution images.

Resolution: When Internal Image Trapping is enabled, this pulldown determines the resolution at which image colors are used to determine trapping. This setting does not affect the resolution of the image. The maximum resolution available is the output resolution, and one or more lower resolutions are also available. Reducing the resolution will speed up trapping when Internal Image Trapping is enabled, but has no effect when it is disabled.

Trapping Set / Save As / Delete: Once you have created a useful group of trapping options, you can save them as a Trapping Set and they will be available in the pulldown menu so you can recall them later. You may also Delete sets from the list.

For more information regarding In-RIP Trapping or any other Symphony feature, contact a sales representative today.