In GMG ColorServer version 5.1.1, an improved handling of overprinting effects was introduced for PDF processing without flattening.
How does it work?
If the Flattening option is switched off during PDF processing, the flattening will be done in the RIP.
Let us explain the improved behavior on the following element.
The element consists of two squares colored with solids of the process color Cyan and set to overprint. A color conversion without flattening was applied in GMG ColorServer version 5.1 (or lower) and 5.1.1. The results are shown in the following image.
Comparison of the old and new behavior when processing overprinting objects without and with flattening in version 5.1.1.
The new PDF processing algorithms ensure that overprint effects will be respected and the final design will be intact in version 5.1.1.
However, slight color shifts might be visible or measurable. If color accuracy is your highest priority, flattening is still the way to go.
With the Flattening option deactivated as shown in the middle, the overprinting area will show slight color shifts in the overprinting areas. If flattening is done before the color conversion (Flattening option activated) as shown on the right side, you will get correct results.
Please note that, however, reliable color accuracy in areas with overprints and transparencies can be achieved only with flattening.