I know that, if a picture file has metadata (let's say some keywords), these data may reside in the file itself, or in some sidecar file (or in both, I assume). Is it possible to establish which of these is the case for a specific picture file and its metadata?
Metadata is generally stored in the Organizer catalog. Optionally it can be embedded in files from the Organizer menu:
File >> Save metadata to files
Most file types can embed metadata with the exception of proprietary raw files e.g. Canon CR2, Nikon NEF. These files store information in a sidecar file usually found in the same folder as the original.
You can check files with embedded metadata by opening in the Editor and using the menu:
File >> File Info
Thanks for you swift reply. Even so, I'm a bit disappointed. I would have expected that a program that is meant to be a management program (so, PSE Organizer) would offer a clear overview of the location of all metadata of a particular picture file. If I understand you correctly, however, I would have to open another program (PSE Editor) to establish which of the metadata are embedded. I would then have to return to the Organizer and 'subtract' these embedded metadata from the total metadata in order to arrive at the catalog-only metadata. Well...
Just to make sure: this is no criticism of you (I'm very happy with your response). Instead, it's criticism of PSE.
You can also view the info from the Organizer and append or overwrite data. Click the three dots in the metadata panel on the right. See image below.
Is there somewhere a list which of all data fields may be embedded and which ones have to reside in a separate sidecar file?
Depending on the file type, of course.
Raw files require xmp sidecar files but for jpegs, psd or tiff files the metadata will be embedded in the metadata header of the media file itself.
The normal tags, captions, ratings, notes, date_taken, will be written, but the grouping information like albums, stacks and version sets have no meaning for a single file and nothing will be written. If your concern is about face recognition or geotagging, please explain what you would like.
You can browse the various metadata from the editor or from the organizer. As mentionned by 99jon, you also have the ability to edit the IPTC fields directly in the media file independently from the catalog.
A similar question would be which metadata is automatically written to the file (or xmp) when updated in the catalog. For instance, edited captions are indeed written to files...