Update files from catalog
In this post, I am not using "Edit IPTC" nor "Edit XMP" dialogs
So, settings are
only in "Settings>Metadata screen .
Let us use a photo that has a category, and where IPTC and XMP spaces are empty (Tools>metadata>Clean)
TEST #1
- No options ticked
- "Update files from catalog" Will create XMP sidecar file with exif data.
Known behaviour, but still so strange : "Create sidecar" was not ticked ...
TEST #2
- Only 1 option ticked : "Export categories..." ( No IPTC and no XMP options)
- "Update files from catalog" will create XMP fields.
Bug1 : "Create XMP" is not ticked
(Info : if iptc or xmp data were already present, keywords are updated. That's OK, see last lines of this post)
TEST #3
- "Export" and "Create XMP" are ticked
- "Update files from catalog" will create XMP fields with Keywords. No bug here, OK
- (But why are the rating and labels fields always created if not needed ? )
TEST #4
- "Export" and "Create IPTC" are ticked
- "Update files from catalog"

Bug1 : "Create XMP" is not ticked , XMP fields are created
Bug2 : "Create IPTC" is ticked and IPTC fields are not created
(
Yes, I can reproduce now ! Previously, all my photos had already an iptc space, sometimes only CodedCharacterSet = UTF 8 only shown in ExifTool tab)
TEST #5
- "Export" and "Create IPTC" and "Create XMP" are ticked

Bug2 IPTC fields missing
---
(Info : If we first add a caption in IPTC and XMP fields, "Create IPTC" and "Create XMP" options are not significant , because IPTC and XMP are already existing, no need to create them. In this case, IPTC Keywords and XMP Subject can always be exported with "Update files from catalog" function.
But existing keywords will be erased without warning !
bug 3 ? )
Edit : 14/06/2022 Working in progress on these bugs with XnView developper