After I reported about the disastrous PDF/X-4 compatibility of the new Affinity Publisher a few weeks ago, a reader drew my attention to another problem.
When preflighting with the PDFX-ready preflight profiles, a warning is generated regarding the output intent for PDF/X files of Affinity Publisher V1.7.1 and V1.7.2 with the message “!!! Output Intent not suitable for printing (unknown ICC profile)”:
The output intents in the PDFX-ready preflight are checked not by the name of the ICC profile (since this is sometimes changed by users), but by the MD5 checksum (hash value) of the embedded ICC profile. Our preflight profiles contain the hash values of about 100 standard ICC profiles (see Output-Intent-Regelwerk).
The MD5 checksums of the output intents of Affinity Publisher do not match the values of the original ICC profiles, because Affinity Publisher (or the “Little CMS” module used in the program) changes the CMM entry in the metadata of the original ICC profiles (overwrite with “lcms”; see cursor arrow at the bottom of the two screenshots). This of course changes the hash value of the MD5 checksum and therefore generates the preflight warning.
The actual function of the ICC profile is not changed. Therefore, the modified MD5 checksum would not be a problem … if there was no danger that subsequent color servers or output systems would also use these hash values to determine whether the output intent matches the selected target profile. If these are not identical, a color conversion is triggered. Since this is a pure ICC color conversion that uses a three-channel Profile Connection Space (Lab), the black separation of the original changes.
Different hash values can trigger unwanted color conversions, which may lead to a four-color black. Or grayscale is converted to 4C. Of course this is not desired!