Today’s Question: I have noticed for some thumbnails [in Adobe Lightroom] there is an icon with three lines and an upward-pointing arrow at the upper right corner of the image. When I click that icon I get a message: “The metadata for this photo has been changed by another application. Should Lightroom import settings from disk or overwrite disk with those from catalog?” What does this mean?
Tim’s Quick Answer: The icon you refer to indicates that updates have been made to the metadata for the photo outside of Lightroom, meaning the metadata contained within the file on your hard drive does not match the metadata within the Lightroom catalog.
More Detail: Because Lightroom makes use of a catalog to track information about your photos, it is critically important that all updates you apply to your photos be applied within Lightroom. If any metadata updates (or other changes) are applied outside of Lightroom, you won’t see the update within Lightroom and you might even cause a situation where your photos can’t be found.
Even processing a RAW capture outside of Lightroom can create a metadata mismatch, since the adjustment settings from Adobe Camera Raw can be written to an XMP sidecar file for the image. So again, the key is to not perform any work with your images outside of Lightroom, to help ensure that the Lightroom catalog always reflects the latest (and accurate) information about your photos.
When there is a metadata mismatch, you have the choice of either replacing the information contained in the actual image file with the information in your Lightroom catalog, or to replace the information in the Lightroom catalog with the information contained in the source image file. The correct decision here depends on which updated information you want to keep.
For example, if you added a keyword to a photo through Adobe Bridge, and then realized you should have applied that update within Lightroom, you could choose the option to import the settings from the source image.
However, it is important to keep in mind that when you update the metadata to correct the mismatch, you aren’t able to merge all of the information. That means some information might be lost. If you added a keyword to a photo using Adobe Bridge, then added another keyword to the same image in Lightroom, updating the metadata in either direction will cause one of the keywords to be lost.
If you are confident that no updates were made outside of Lightroom that you need to have reflected in Lightroom, you can simply choose the option to have Lightroom overwrite the metadata for the source image based on the information in the catalog (or simply ignore the metadata mismatch icons if you prefer). If you need to retain the information from the source image (replacing the information for that image in the Lightroom catalog) you can use the option to import settings.
And again, be sure that all updates and other workflow tasks are initiated inside of Lightroom, to help ensure you won’t need my “Cleaning Up Your Mess in Lightroom” video training course (https://www.greylearning.com/courses/lightroom-mess).