When you are using raw files such as Nikon NEF, Canon CR2 or Pentax PEF, all the IPTC, keywords and various settings are stored in the XMP file. The XMP file is also called a sidecar, because it “rides alongside” of the photo.
The XMP sidecars contain the metadata, the keywords and the adjustments made to an image. By default, Lightroom does not automatically write to the sidecars into the folder containing your images. The metadata, keywords and adjustments are saved but only in the Lightroom SQLite database. Other programs such as Photoshop, Corel Paint, Photo Mechanic… will not know anything about the metadata, keywords and adjustments that you have made. They look for the XMP sidecar for that information.
Now if you use DNG files, all of the metadata, keywords and adjustments are stored in the DNG file itself. Lightroom or any other editing/inventory tracking will not create/use an XMP sidecar.
Lightroom: Automatically write changes into XMP
- That’s the major reason why I convert all my photos to DNG. I only have to deal with only 1 file.
- Why did I switch from my cameras raw to DNG? Because between backups, restores and file moves, I forgot to deal with XMPs and lost thousands of XMPs files. It was very painful.