Legacy IPTC Digest vs IPTC Digest

[blue-j]

The PSIR namespace has "IPTC Digest" to compare with the file's to see if the IPTC and XMP are in sync; however, the Photoshop XMP space has something called "Legacy IPTC Digest" sometimes, and WITHOUT the PS one.

Should we still compare the XMP "Legacy IPTC Digest" value with the current?

Also, from the PSIR page in the ExifTool documentation:

(this tag indicates provides a way for XMP-aware applications to indicate that the XMP is synchronized with the IPTC. The MWG recommendation is to ignore the XMP if IPTCDigest exists and doesn't match the CurrentIPTCDigest. When writing, special values of "new" and "old" represent the digests of the IPTC from the edited and original files respectively, and are undefined if the IPTC does not exist in the respective file. Set this to "new" as an indication that the XMP is synchronized with the IPTC)

I have not found this guidance in the version 2.0 guidelines; was it in a previous version's?  Is anyone doing this?  I have never seen "new" or "old" as a value.

I simply do not know how to deal with MWG guidelines anymore since they seem to have disappeared...

- J

[Phil Harvey]

I have definitely seen Adobe applications that ignore the XMP if the IPTCDigest is wrong.

XMP:LegacyIPTCDigest should not be used as far as I know.  I don't know if it was ever part of a specification.

Photoshop:IPTCDigest should be deleted as far as I am concerned because it has only been known to cause troubles.  The guidance appears on page 26-27 of the MWG 2.0 recommendation.

- Phil