Use of IPTC Tags
The way the IPTC tags are read currently, any matched field that is not aready being used is read from IPTC. This means once read, the IPTC tags won't be read again from that photo, unless the tags are cleared in MC. The IPTC and existing tags are not merged.
Here are the current IPTC tags being read, and MC tags the are mapped to (also subject to change):
BYLINE -> Artist CREDITS -> Notes DATECREATED ->[changed] Date CITY STATE, COUNTRY ->(combined) Places COPYRIGHTNOTICE ->Copyright (read only) CAPTION ->(same: no longer Comment) CATEGORY->Genre KEYWORDS->(same)
Information that can't be stored in those tags gets saved in MJMD tags.
Keywords from IPTC maps to MC's Keywords. IPTC Keywords is the only thing Windows Photo Gallery seems to recognize.
MC saves IPTC tags to any JPEG it tags.
MC populates the Aperture, Camera, Date, Flash, Focal Length Format, ISO and Shutter Speed fields from EXIF information in the JPEG file while importing that file.
MC Photo Editor Effect on Tags
Is file metadata/tagging preserved? EXIF?
It depends on what you do, and how MC is setup. If you perform a "save as.." in order to preserve the original file, a new file is created, and it has absolutely no metadata whatsoever. No file tags, and no database info. It will be a brand new file that will need to be tagged from scratch. If you simply save the edits over the top of the original file, then you still end up with a brand new file with no metadata whatsoever, but you will still have any previous tagging info for that file in your MC database. You can use the update tags from library to re-write the tags. EXIF info is permanently lost. Also, in this scenario, if you have auto import watching the folder the image resides in, you need to get that tag update done before Otto wakes up (either be quick, or unwatch the foder) because Otto will see that, essentially new, file as having received external changes and promptly set about updating things!