Today’s Question: Recently I’ve noticed that some of my folders containing RAW files do not have any of the associated XMP files. Do you have any ideas as to how this could have happened other than my somehow inadvertently deleting them?
Tim’s Quick Answer: A lack of XMP files would indicate either you have not made any updates to some of your raw captures, you have disabled the option to automatically save changes to the original captures in Lightroom, or you have somehow inadvertently deleted the XMP sidecar files.
More Detail: The XMP sidecar files you might see alongside your original raw captures are there to contain any metadata you’ve added to the photos. This can include standard metadata such as keywords and star ratings, for example, as well as other information such as adjustment settings from Adobe Camera Raw or Lightroom.
With most image types, when you update the metadata for an image that metadata is simply written to the file itself. This would be the case for JPEG or TIFF images, for example. But for original raw captures, the idea is that you don’t want to risk harming the original capture data, and so metadata will be stored separately.
If you are using Adobe Bridge to manage your photos and Adobe Camera Raw to process your raw captures, metadata would not be written to an XMP sidecar file unless you have actually processed the image with Camera Raw or have updated metadata such as with Adobe Bridge. If you’ve not worked with a particular raw capture, an XMP sidecar file would not be created for that capture.
With Lightroom Classic CC, XMP files are only created if you have specifically chosen to save metadata for your photos. You could use a menu command (Metadata > Save Metadata to Files), or enable the option to automatically write metadata to files on the Metadata tab of the Catalog Settings dialog. If you have not made use of one of these options (or otherwise created XMP files with other software) there would be no XMP files for affected raw captures on your hard drive.
And, of course, it is possible that you could have inadvertently deleted the XMP files from your hard drive. Doing so would cause you to lose metadata updates for your photos (unless those updates are contained in a Lightroom catalog, for example), but would not cause any problems with the original raw captures.