Today’s Question: To clarify, can an entire Lightroom Classic catalog be built strictly from a complete set of XMP files?
Tim’s Quick Answer: If you make use of the option to save metadata to the source images in Lightroom Classic, you can recover most of the information about your photos if you lose your catalog, provided you still have the source images and the related XMP sidecar files.
More Detail: Today’s question was a follow-up asked during my recent all-day GreyLearning Virtual Photo Conference. It was in response to comments I made about being able to recover from a lost or corrupted catalog in Lightroom Classic by importing photos into a new catalog based on the XMP sidecar files saved along with the original raw captures.
If you turn on the “Automatically write changes into XMP” checkbox on the Metadata tab of the Catalog Settings dialog in Lightroom Classic, standard metadata updates (such as star ratings and keywords) are saved to the source image files on your hard drive, or to XMP “sidecar” files for proprietary raw captures.
It is important to keep in mind that enabling this option does not preserve all information from your Lightroom Classic catalog. Some of the features specific to Lightroom Classic, for example, are not preserved when metadata is saved to the source images. For example, collections, virtual copies, and pick/reject flags are not preserved in this way.
So, I still recommend that you regularly back up your Lightroom Classic catalog. However, by enabling the option to save metadata to the source images you have the additional opportunity to recover from a lost catalog by simply importing your photos into a new catalog.
The XMP sidecar files represent metadata supplements for the source raw captures. Therefore, you would need to have both your original raw images and the accompanying XMP sidecar files in order to use this recovery process. You could then simply import those photos into a new catalog, and retain standard metadata values and Develop module adjustments, but not all information that had been in the original catalog.
So, this XMP option isn’t perfect as a backup, but it does provide some additional peace of mind in addition to a good workflow for backing up your photos.