"EXIF schema for additional EXIF properties" silently disappeared since XMP Specification Part 2 - 2016 #23
Description
Until "XMP Specification Part 2 - Additional Properties" revision of 2008, aux:Lens, aux:SerialNumber existed in the aux namespace, see the following excerpt:
Possibly they may have been replaced by exifEX:LensModel and exifEX:LensSerialNumber in CIPA DC-010-2012 (the separated document specifying all of the Exif properties since XMP Specification Part 2 of 2016), however this is not documented either in the current specification pdf document or the Markdown rendition.
I believe the two properties should be either fully reinstated in "XMP Specification Part 2" or reinstated as deprecated.
This issue has been first created in the pdf-issues repository but moved to this one after the PDF TWG discussion.