What would be the command to create a new tag (I am assuming XMP) to for text (json), and, if so, how large can that tag be?
The goal is to copy ALL a photos metadata into a another tag--i.e.create a backup--so I and others can CRUD the other fields.
I am prioritizing (no) sidecars, but I would also like to add my own history tag(s) (Timestamp,Editor).
There's no command to create a new tag. You have to create a definition for your new tag. From there, you would either save it as a separate config file and use the
-Config option (https://exiftool.org/exiftool_pod.html#config-CFGFILE) to activate it or you would add it to your
.exiftool_config file.
Creating an XMP tag would be the best, as this quote from Phil says about the size
Quote from: Phil Harvey on August 21, 2018, 09:59:28 AMExifTool doesn't impose any length limitation on PDF or XMP metadata.
See the
example.config file (https://exiftool.org/config.html) for details.