Today’s Question: I have started using smart previews [in Lightroom] so I can do most of my editing on a mobile device or on my laptop with the photos drive detached so it doesn’t spin all the time.
When I open Lightroom with the photos drive attached, will the XMP sidecar files that have new data from Lightroom Mobile editing or from editing with the smart previews get updated automatically or do I have to do something to ensure that they get updated?
Tim’s Quick Answer: If you have enabled the option to have Lightroom automatically update the XMP sidecar files, those updates will begin as soon as the source image files are available. The Lightroom catalog will be updated based on changes made via Lightroom Mobile (or Lightroom Web) as soon as Lightroom is connected to the Internet for synchronization.
More Detail: There are now a variety of ways you can work with your images in Lightroom, including the use of a feature-limited version of Lightroom on mobile devices and the ability to work with Smart Previews in Lightroom on a computer even when the source photos aren’t available.
In terms of working on mobile devices and with Smart Previews, the Lightroom catalog will be updated to reflect the changes you’ve applied as soon as synchronization is possible. That basically means that as soon as all of the devices in question have been connected to the Internet, updates will be synchronized. So, for example, when you apply an adjustment to an image with the mobile version of Lightroom, once your mobile device and your computer have been connected to the Internet Lightroom will be able to synchronize the data.
If you want the XMP files for RAW captures (or the actual image files for other captures) to be updated in addition to the Lightroom catalog, you can enable automatic updates. To enable automatic updates, go to the Metadata tab in the Catalog Settings dialog, which can be found on the Edit menu on Windows or the Lightroom menu on Macintosh. Then turn on the “Automatically write changes into XMP” checkbox, and Lightroom will update the source images with metadata updates based on changes you apply in the Lightroom catalog.
It is important to note that not all changes you apply in Lightroom can be written out to the XMP sidecar files (or source images). In general, features that are specific to Lightroom (such as pick and reject flags, collections, virtual copies, and more) cannot be saved in this way, and will only exist within the catalog.