Does Lightroom write DNG edit settings into the file, and can they be kept in a sidecar instead?

Asked 10/27/2014

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I know Lightroom edits are non-destructive because they only change metadata/settings, not the original raw image data. With CR2 files, Lightroom can store those settings in a separate .xmp sidecar instead of modifying the raw file.

With DNG, it seems the settings are written into the DNG file itself. Does that mean Lightroom has to rewrite the whole DNG whenever metadata or develop settings change, which could affect snapshot-style backups, bandwidth, or read-only files? Is there any way to keep DNG edit metadata separate, like sidecars for other raw formats?

metadataraw-workflowlightroomdngxmp

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

11y ago

2 Answers

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I don't think there's any way around the issue of the larger DNG file size causing more issues with backups, since any change to the image's metadata/processing instructions will write out the entire file again. However, you can create a .xmp sidecar file from a DNG file with exiftool:

exiftool -xmp -b -w xmp <path_containing_dngs>

And, in fact, if you open a DNG file with Microsoft Word, you can copy and paste out the XMP data, according to this website.

So no, I don't feel any less secure with the XMP information embedded within a DNG file than outside it in an external .xmp file. And, actually, I don't really feel that insecure with all the information in the .lrcat library file, either, since it's just an SQLite database, and works with all the SQLite tools for data browsing and dumping. Sure, databases go corrupt, but if you need to can opener data out of one, better it be a widely-adopted open source SQL-based one with a bunch of tools out there for you to do so. ;)

Also, apparently, if you make the DNG file read-only, that's the perfect solution, as Lightroom will then make a .xmp sidecar file for the DNG.

Addendum: I just tried Metadata -> Save Metadata to File in Lightroom 5.6 (on OSX, 10.8.5), and got .xmp sidecar files for a folder's worth of DNG files.

Originally by user27440. Source · Licensed CC BY-SA 4.0

user27440

11y ago

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AI Answer

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Yes—Lightroom can embed develop settings/XMP metadata directly inside a DNG file. That is still non-destructive: it does not alter the underlying raw image data, only the metadata stored in the container. The tradeoff is practical rather than photographic: when embedded metadata changes, backup/snapshot systems may treat the DNG as changed, which can be less efficient than updating a tiny .xmp sidecar. If the DNG is read-only, Lightroom also won’t be able to write those embedded changes. If you want the metadata separate, you can extract/write XMP sidecars for DNGs with tools such as ExifTool, for example: exiftool -xmp -b -w xmp So the concern is mostly about workflow, backups, and file management—not image preservation. Embedded XMP in DNG is generally no less safe than sidecar XMP; it’s just stored in a different place.

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UniqueBot

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11y ago

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