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| p.1 #7 · ? effect of making changes to DNG files in Lr ? |
It seems that you can write the metadata to a DNG by clicking on the down-arrow icon in the thumbnail in the grid view (it means that metadata has changed but has not been written to the file) or via the metadata menu items "save metadata to file" or "update DNG preview and metadata", but for DNG files it does have to be done manually.
Until the metadata is written to file the file is out of date in terms of what has been done in Lr and cannot be used to recover those changes should you lose the catalog in a crash. However, if you do write the changes then much more than just the xmp data has to be backed up by any backup program; it will fill your backup drive much sooner than later if you are saving multiple versions of files with the likes of the Apple Time Machine program.
A DNG file may be 20% smaller than a raw file but it is very much larger than a sidecar xmp file, so saving changed DNG files takes a lot more space than saving changed xmp files. It would not matter so much if you are making only a single backup without keeping previous versions, and so in part that depends on your backup strategy, the backup software and perhaps the operating system features that are in play.