KB179226090: Imaging Engine - Differences between Esko screening in Imaging Engine and FlexRip

Question

Why is Esko screening in Imaging Engine different from FlexRip?

Answer

In the Imaging Engine 16.0.2 advanced screening options, the user can select the "Esko" screening model. When selected, Imaging Engine will apply screening information from the PDF file in a very similar way as in FlexRip, giving the results that users of FlexRip would normally expect to see.

The aim of the FlexRip halftone model is to respect the intent of the file. Mostly FlexRip will use the halftone of the topmost visible element, but if PDF transparency is used and image or shading content is shown then the halftone of the image or shading will be used.

There are, however, a few situations where this does not happen in FlexRip. These cases are not common, but if the screening in Imaging Engine is different from that in FlexRip it should always be because Imaging Engine is following the model more closely and better respecting the artistic intent of the file.

Examples might be as follows:

1. For overlapping objects inside a transparency group, FlexRip will sometimes use the halftone of a flat tint even though an image or shading is visible. In Imaging Engine there is a stronger preference for the halftone of the image or shading.
2. If a non-separable blend mode is used (Hue, Color, Saturation or Luminosity), FlexRip cannot always correctly determine which halftone to use. In Imaging Engine, the normal rules are followed.

There are two other situations where Imaging Engine does not select the same screen as FlexRip. In both the situations, Esko believes that the Imaging Engine behavior is an improvement over FlexRip:

1. In FlexRip, a completely transparent object can still influence the screening whereas in Imaging Engine it does not.
2. In Imaging Engine, the halftone is determined per pixel. For instance, at the point where a shadow effect fades away completely, Imaging Engine will always use the halftone of the object below (since the top object has become completely transparent). FlexRip is unable to do this, and an object with a shadow can still influence the screening even where the shadow effect has completely faded.