High time that DxO breaks the broken paradigm and starts not to just read incoming XMP star ratings but write its own ratings and select flags back to the XMP file where it belongs for proper interoperability. IPTC keywords, headline, description/caption, copyright info also belong there. Photolab should stop worrying about a proper DAM and worry about supporting keywords, headline/title, description/caption in their mini-EXIF viewer-editor just as they support copyright info (a successful implementation, btw).
The IPTC fields most DxO Photolab users need access to are exactly those ones, with perhaps adding location (although there are just too many location fields to make location an easy add). Users who want more than headline/title, description/caption, copyright info and keywords are probably require something like Photomechanic or iMatch which really can not and should not be shoe-horned into Photolab. Lightroom’s own EXIF handling is inadequate, while CaptureOne has gone overboard with IPTC fields:
While it pains me to say something nice about the people who made subscription-only software mainstream, Lightroom seems to have the right number of fields.
As far as I know Lightroom writes that metadata into the XMP file (the preference has to be set on a per-catalogue basis which I find too granular and likely to cause user-error: should be set once globally by a user).
For tif or jpeg files, the information is stored within the tif/jpeg which is okay as those file formats are intended to carry XMP/EXIF/IPTC information and the applications which understand XMP know to look within the file too.
Since Photolab users work almost only with RAW files (I did try to finish my Fujfilm jpegs in Photolab for a couple of months but found the RAW to TIFF in Iridient Developer to Photolab to jpeg output workflow far too heavy) the important part here to keep in mind is writing that metadata and those metadata changes back into the XMP files. It’s somewhat less of an issue than I imagined as Photolab will write metadata changes into its own jpeg/TIFF output.
In my own workflow I start working with metadata again post-Photolab (was using Adobe Lightroom 4, currently trialling with much better results Photomechanic Plus) so any changes to metadata should be in the XMP so I can see changes made to metadata in Photolab. The big issue is with star ratings as I may wish to browse that selects folder with Photomechanic or any other fast efficient RAW viewer (does not include Photolab) and see changes made to star ratings or flags. It’s really a matter of principle. There’s no good reason for DxO to behave badly here by storing shared data like star ratings and select flags, and perhaps later keywords and captions when the accepted vessel for this information is an XMP sidecar.
I hope this information and these examples help some others to puzzle through the challenges of integrating Photolab into a DAM and metadata friendly workflow. Even more, I hope it inspires DxO developers to fix Photolab’s lapses with metadata (store metadata once and for all in XMP sidecars where it belongs; for bonus points, add support for headline/title, description/caption, keywords to the existing EXIF editor).
PS. If DxO improves the EXIF editor, storing metadata in XMP sidecars suddenly becomes much, much more important. Right now the most prudent way to handle metadata in DxO Photolab is to more or less ignore it and not touch it.