Converting proprietary raw into DNG: how much do I lose?

Discussion in 'Digital Photography' started by JD, Jun 6, 2005.

  1. JD

    JD Guest

    Hi, when I convert a raw file from my Pentax *istDs with Adobe Raw
    Converter, the original *.PEF file of 11030 Ko becomes a *.DNG file of 6394
    Ko.

    What am I losing? If I'm not losing anything, why does the *.PEF need to be
    so big?

    Which one should I keep both for archiving?

    Regards,

    Jean.
     
    JD, Jun 6, 2005
    #1
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  2. JD

    Bill Hilton Guest

    > Jean asks ...
    >
    >What am I losing? If I'm not losing anything, why does the *.PEF need to
    >be so big?
    >
    >Which one should I keep both for archiving?


    Here's a link to the best write-up I've seen on what you lose and why,
    with a suggested workflow by well-known Photoshop guru Jeff Schewe ...

    http://photoshopnews.com/2005/05/23/dng-workflow-part-i/

    Bill
     
    Bill Hilton, Jun 6, 2005
    #2
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  3. JD wrote:
    > Hi, when I convert a raw file from my Pentax *istDs with Adobe Raw
    > Converter, the original *.PEF file of 11030 Ko becomes a *.DNG file
    > of 6394 Ko.


    I have a Pentax *istD, and that has PEF files of about 13MB, instead of
    about 11MB for the *istDS. The DNGs are about 6MB.

    > What am I losing? If I'm not losing anything, why does the *.PEF
    > need to be so big?


    The PEF from my *istD is probably not compressed at all. (If it holds
    the 12-bit sensor data as 16-bit aligned, then a 6 megapixel sensor
    will take about 12+MB). The PEF from your *istDS is probably (lossless)
    compressed a bit in the camera. The DNG Converter optionally uses
    LOSSLESS compression, based on a lossless-type of JPEG compression. It
    doesn't lose anything by this compression.

    Try an experiment. Use the "don't compress" option in the DNG Converter
    when converting from PEF. I'll bet that the result is about 13MB, but I
    don't know for sure. Or try running your DNGs through the DNG Converter
    again, (it will happily convert them, of course), with compression
    switched off. I'm sure the resultant DNGs will be about 13MB.

    > Which one should I keep both for archiving?


    Against the advice of Adobe and others, I only keep the DNGs. In fact,
    I now convert straight from the card, so I never see the PEFs on my PC.
    That is because I don't intend to use any Raw processor that doesn't
    accept DNGs. (There is "secret" Pentax stuff in the PEF which Adobe
    doesn't understand. The 3.1 DNG Converter stores it in the resultant
    DNG, but doesn't use it. If you need it in future, it would be possible
    for code to extract it, although there is no "off the shelf" code yet).

    But "don't try this yourself" unless you are confident you know what
    you are doing. If you will ever want to use a Raw processor that
    doesn't accept DNG, either keep the original PEFs, or embed the PEFs in
    the DNGs, (an option in the DNG Converter), so that you can extract
    them later.

    --
    Barry Pearson
    http://www.barry.pearson.name/photography/
    http://www.birdsandanimals.info/
     
    Barry Pearson, Jun 6, 2005
    #3
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