A photographer’s best friend: the XMP file! I always get really psyched discussing these small, but powerful files with my clients, because it means that they are sending me their raws to work on. XMP sidecar files are XML files that correspond to your raw images, which reflect and keep track of the non-destructive changes you make. The good news is that your original raw files remain, well, raw… and any “changes” you make are actually completely reversible! Generally, these changes are stored in your Lightroom catalog, but the XMP provides a way of externalizing them so they can be used by other image processing software like Adobe Camera Raw (Photoshop)
You may (or may not) know that there are several key items that are NOT stored in an XMP – surprising, because they are that great. So what isn’t stored in an XMP?
- Edit History – XMPs store the metadata and develop module settings for the current stage of an image when the file was last updated/written. You can not undo or revert to a previous change.
- Virtual Copies – if your finished image is a virtual copy, those changes are only reflected in the Lightroom catalog
- Pick Flag – the white, black, and grey flags which indicate your picks, rejects, and unreviewed files (note that star ratings ARE reflected in XMPs)
- Collections and Stacks – these are “catalog-isms” so they do not go along with the images in the XMP
- Disabed Edits – the XMP will not include information about an adjustment you have toggled off
**These items can be copied between catalogs with “import from another catalog” and “export as catalog” options checked. If any of these items are valuable within your workflow, I’d suggest relying on catalogs and XMPs equally.
In case you are not sure what IS stored in an XMP file:
- EXIF/Copyright/Keywords – These include some overlap between information at the time of capture and at the time of import, such as copyright data, capture time, keywords, and any metadata presets
- Develop Module Changes – the value of all the sliders and the position of all your adjustment brushes are stored, hooray!
- Snapshots – this is a cool one. If you create snapshots inside of Lightoom, those snapshots and the development settings at each snapshot are stored too. A good way to work around the lack of edit history.
- You can have Lightroom automatically write to and update the XMP file for every change you make to an image (recommended) or you can do those things manually by choosing “save metadata to file”. The XMP files will be stored in the same directory/folder as your raw image file, and have the same file name with an .xmp exension.
- Make sure to back up your catalog before you remove anything or make any large changes. If something unexpected happens, you can revert to a previous version of your catalog and adjust accordingly.