Why is black content sometimes color managed to CMYK in Imaging Engine?
When processing some files, Imaging Engine can produce output that is color managed in an unexpected way. In particular, black objects such as shadow effects can sometimes be color managed to CMYK while RIPping, causing the object to be printed using multiple process inks.
Why does this happen?
This typically happens when the PDF file was generated from InDesign, but it could happen with other PDF generating applications too. PDFs exported from InDesign typically have a “Page Group” color space, but it is also possible to specify an "Output Intent" profile (which is also a kind of color space). When both are present in the PDF, there should be an extra color space conversion from the "Page Group" color space to the "Output Intent" color space.
Both color spaces can be seen in Acrobat by using the Output Preview tool as shown in this screenshot:
Imaging Engine does perform this extra color space conversion, but FlexRIP and older components of Automation Engine that require Normalized PDF do not, because they do not take the "Page Group" color space into account. Similarly, ArtPro+ does not take this color space into account. The result is that, although the output of Imaging Engine is correct, its color management might be different compared to the view in ArtPro+ and other Esko applications.
Is there a workaround?
Yes, there is a workaround of sorts, depending on requirements:
If correct color management is a priority, then nothing needs to be done because the Imaging Engine output is correct.
However if it is more important to have the same color management in Imaging Engine and ArtPro+, or to more closely match Imaging Engine output with FlexRIP output, then running the PDF file through the "Export to Normalized PDF File (Embed All)" task in Automation Engine will cause the "Page Group" color space to be removed. The extra color management step will then not be done by Imaging Engine either and objects that are viewed as black only will also be RIPped only to the Black separation.
If you are already in a native PDF environment and don't want to normalize the file then also a PitStop action list can be created with the action " Change blending color space" (https://www.enfocus.com/manuals/Extra/Actions/22/home.html#en-us/common/act/concept/36.html) where you can either set them to device color spaces like "DeviceCMYK" or deleting them by setting it to "none". Also it is possible to check on blending color spaces via action list.