PL will keep all informations from embedded data (Exif/Maker notes) for output image.
About XMP, there are several parts in the content.
if the “preserve metadata in XMP sidecar for RAW images” option is checked, PL will keep all informations from XMP sidecar
if this option is unchecked from preferences, output image will have only few information from XMP sidecar (like rating, orientation)
About rating in PL and output image: the priority is set as following: PL > XMP > EXIF. By default, rating from XMP/Exif will be imported in PL (yellow star), once we change the rating in PL, the highest prio will be taken for PL and output image will have the rating from PL.
About keywords, PL won’t display keyword/description/comment from Exif part. Currently ONLY keywords from XMP sidecar will be imported and displayed in PL.
XMP writing (inside PL) part has not yet been implemented, but may be in the near future.
So with an example from obetz, only “an ugly beast” keyword will be used in PL.
So please dont hesitate to share us your thinking on this topic.
thanks for your detailed answer especially about the “preserve metadata in XMP sidecar for RAW images” option, htran.
We need to be cautious about the wording: “XMP” is used to name the sidecar but also for an information section inside the image file or sidecar. Sorry that I was not that clear in my OP.
I think I remember that XMP data embedded in the raw file is also read by DxO Photolab if there is no XMP sidecar, IOW: If XMP-dc:Description embedded in the raw file contains “a nice dog”, and there is no XMP sidecar, the exported jpeg will have “a nice dog” in it’s XMP section.
Will an IPTC IIM section be read and exported by Photolab?
Generally, I think it is a good idea that DxO Photolab gives the sidecar data higher priority than the metadata embedded in the image file. If an application creates a sidecar, this is very likely the most recent container.
Perhaps DxO can explicitly point out in the Photolab documents that this is intentional and will remain unchanged.