Why embed the original RAW file inside a DNG?
Asked 4/21/2012
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I'm considering converting my Nikon NEF files to DNG so Lightroom can store metadata in the file itself and improve performance with fast loading/indexing. Lightroom also offers an option to embed the original RAW inside the DNG, but that nearly doubles the file size. If DNG is supposed to contain the same image data, why would someone want to embed the original RAW? Does converting to DNG lose any information or omit anything from the camera's native RAW format?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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Disclaimer: this is what I recall from having read about the prospect of going all-DNG for file archives. I might be a bit fuzzy or off.
DNG is a standard format, with specific properties. The raw files produced by a camera have a unique format, which does not precisely map to the DNG spec - camera manufacturers are being a bit cagey about file formats.
Because there's no exact match between raw and DNG, some raw file properties do not get carried over to the resulting DNG file. So to get access to the complete raw data, the actual raw file needs to be at hand. Which will be the case if it is embedded within the DNG.
In the end, it seemed to me to be too much hassle going back and forth between raw and DNG, so I decided to keep using "raw" raw files. It would be nice to have the metadata embedded within the image file, rather than contained in a sidecar .xmp, but I made a trade-off. Your mileage may vary.
Originally by user26. Source · Licensed CC BY-SA 4.0
user26
14y ago
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Generated from our catalog & community — verify before relying on it.
Embedding the original RAW in a DNG is mainly about preservation and reversibility. A camera maker’s native RAW format may contain proprietary or model-specific data that does not map perfectly into the DNG specification, so some nonessential or manufacturer-specific information may not carry over exactly in conversion. By embedding the original file, you keep the option to extract and use the untouched native RAW later if needed.
That means the trade-off is simple:
- DNG only: smaller files, simpler metadata handling, possible workflow/performance benefits.
- DNG + embedded original RAW: much larger files, but maximum backward compatibility with the camera’s native format.
If you trust DNG as your archive format, embedding the original RAW may be unnecessary. If you want the safety of retaining the exact original file for future software support or archival reasons, embedding it can make sense. It’s less about image-quality loss and more about preserving any native-format data that DNG may not represent exactly.
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