Today’s Question: I understand the benefits of enabling XMP sidecar files for proprietary raw captures in Lightroom Classic, but what about for Adobe DNG files?
Tim’s Quick Answer: The same benefits of enabling XMP sidecar files for proprietary raw captures in Lightroom Classic apply to Adobe DNG and other supported image formats. The only difference is that for files other than proprietary raw captures the metadata updates are written directly to the source files rather than to an XMP sidecar file.
More Detail: As I’ve addressed previously in the Ask Tim Grey eNewsletter, I strongly recommend turning on the “Automatically write changes into XMP” checkbox on the Metadata tab of the Catalog Settings dialog in Lightroom Classic.
The checkbox is a little misleading, however, because when you enable this option XMP sidecar files are only created or updated for proprietary raw captures. For other supported image file types, including Adobe DNG (Digital Negative) images, the metadata updates will be written directly to the source image file.
It is important to remember that these metadata updates are limited to standard metadata fields as well as the actual adjustments applied in the Develop module. With this option enabled you can view standard metadata updates in other software such as Adobe Bridge, but you should not make any changes to metadata outside of Lightroom Classic.
Perhaps more important is to keep in mind that Lightroom-specific updates that are not included in an existing metadata standard will not be preserved in this way and will only be included in the Lightroom Classic catalog. That includes, for example, collections, virtual copies, Pick and Reject flags, and the history in the Develop module.
Primarily because it provides a backup for what is generally the most important metadata updates in your Lightroom Classic catalog, I strongly recommend turning on the “Automatically write changes into XMP” checkbox. You can read more about how important this is in the context of losing information from your catalog on the Ask Tim Grey blog here: