Anyone Archive Their RAW Images as DNG's

Discussion in 'Digital Photography' started by Russell, May 8, 2005.

  1. Russell

    Russell Guest

    Anyone archive their RAW images as DNG's?

    If so, have you noticed that the DNG file sizes are approx. 1-2MB smaller?
    Why is this, are they compressed slightly during the conversion?
    Russell, May 8, 2005
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  2. Russell

    John Bean Guest

    Depends entirely on what the camera raw file was. A DNG will
    be larger than the Foveon X3F file it was converted from,
    whereas if you start with a Pentax PEF file the DNG will be
    much less than the original. The data in a DNG is compressed
    using lossless JPEG compression.
    John Bean, May 9, 2005
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  3. Russell

    james Guest

    Have you tried using SHN or FLAC on them?
    james, May 9, 2005
  4. Russell

    Paul Furman Guest

    I just began exerimenting.

    That seems a good reason to go through the conversion. There is an
    involved discussion in under the title
    something like "ACR DNG 3.x available for download".
    Paul Furman, May 9, 2005
  5. I just today started thinking about doing so.
    Mine are *drastically* smaller -- my 12.6MB raw files seem to become
    about 5MB DNGs. This makes me very happy. (I have a Fuji S2 with RAW
    files that are, I suspect, a bit unusual; at least their size is
    somewhat unusual).
    David Dyer-Bennet, May 9, 2005
  6. I only archive the DNGs. Once I have DNGs in 2 places, I delete the
    original Raw. This is NOT recommended practice, and contradicts Adobe's
    Yes, there is optional compression. Compression is lossless. It can be
    reversed simply by re-converting with the option switched off. (DNG is
    one of the Raw formats that the DNG Converter accepts as input).

    There is also an option to embed the original Raw file inside the DNG.
    Some people use that for archive purposes, because, while it has the
    convenience of being one file, it offers the ability of regaining the
    original Raw file as a separate file. Obviously, the result is larger,
    but for the Pentax it is not as large as the sum of the 2 separate
    files. I guess that is because the converter compresses the embedded
    original file. (I don't use this option - I just tested it).

    Another potentially useful feature is that, if you use xmp sidecar
    files, the DNG Converter will embed the contents of the sidecars into
    the resultant DNG, so you can archive the ACR settings as well in just
    the one DNG file. (ACR 3.1 also offers this as an option).

    It is absolutely clear that Adobe see DNG, not just as a common Raw
    format, but also as a strategic storage (and presumably transmission)
    format for future Raw workflows. It is becoming as comprehensive at the
    Raw-processing stage as PSD is at the photo-editing stage.
    Barry Pearson, May 10, 2005
  7. Russell

    JPS Guest

    In message <>,
    Perhaps they are separated into bitplanes or nibbleplanes before
    run-length comression. The higher order bits don't change very
    JPS, May 13, 2005
  8. Russell

    JPS Guest

    In message <>,
    Speaking of xf3 files, I must say that after looking at the RAW data in
    some of them very closely, it seems that as three separate greyscale
    channels, or one (combined), noise is extremely low, and readout
    artifacts are almost non-existent. It's just a shame that the data is
    very hard to get accurate hue info from. I'm sure that the SD10 makes
    an excellent camera to make 3.4MP greyscale images from, albeit with a
    little aliasing.
    JPS, May 13, 2005
  9. Russell

    John Bean Guest

    DNG uses lossless JPEG compression, it's fully documented by
    Adobe so no need for guesswork.
    John Bean, May 13, 2005
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