I'm interested in starting to convert my photos to DNG instead of NEF, because it allows Lightroom to embed it's metadata into the actual files, and because the "fast indexing" feature makes significant performance gains on my hardware.

While considering this, I noticed that Lightroom has the option to embed the source RAW into the DNG it creates (if using DNG mode), which puzzles me. It would double the size of the file, and (in theory) the NEF and the DNG contain the same information. Is there some kind of information loss or disadvantage (other than requiring the conversion step in one's workflow) that occurs when being converted into DNG?

2 Answers 2


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.

  • " It would be nice to have the metadata embedded within the image file, rather than contained in a sidecar .xmp". I whole hartedly agree but I am told it is not part of the standard; which seems to be a glaring error. It can be done to some extent in a few pieces of software and well in Photo mechanic. Although the Windows codec will not open a preview of the photo when it has been edited with Photo mechanic.
    – Bonzo
    Aug 3, 2020 at 18:17

Well, the essential premise is that having the original raw format inside gives you the eventual ability to extract it from the file if it were ever needed. I'm not sold on that being especially useful, the DNG format is freely available since Adobe decided to make it so, so I think that DNG gives more future proofing than a closed and proprietary format will.

However, on the other side of the equation, the general cost of storage is relatively low, so if you can afford the space, why not? It can't hurt in that situation.

  • 1
    There's no evidence to suggest that DNG is any more future proof than raw formats. Support for raw formats is accumulative, and older raw formats are not removed from the programs capable of reading them. Apr 22, 2012 at 22:39
  • 1
    @NickBedford - Past performance is not necessarily indicative of future performance.
    – Joanne C
    Apr 22, 2012 at 23:29

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