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Info on lossy DNG?

Jan 10, 2012 5:25 PM

Tags: #export #dng #lossy
  Latest reply: Simon Full, Feb 16, 2012 9:26 AM
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    Feb 10, 2012 9:26 AM   in reply to sandy_mc

    Sandy is right ... I forgot to mention that the DNGs have color profiles embedded, so the DNGs themselves are not actually untagged.  My use of the word "untagged" was meant in terms of the color transform applied (i.e., there isn't any).

     
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    Feb 15, 2012 11:15 AM   in reply to Ryan D Mack

    Hi Ryan,

     

    The noise reduction algorithms in Lr 4 Beta are aware of the relationship between the image size of a downsampled, lossy compressed DNG (e.g., 10 MP) and the full-resolution original (e.g., 36 MP) and can therefore adjust its internal parameters accordingly.  This happens automatically, without any specific action needed from the user.  You can expect noise reduction to be extremely effective on high ISO, downsampled, lossy compressed DNGs.

     

    Hope this helps,

    Eric

     
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    Feb 15, 2012 9:03 PM   in reply to Fuchsteufel

    There is almost merit in using it.

    I'm still just going to buy additional harddrives and keep my images lossless, but man a load of work has gone into providing the lossy DNG's

     
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    Feb 15, 2012 9:59 PM   in reply to MadManChan2000

    I accidentally run the DNG lossy conversion twice over the same image..  Does Lightroom make another pass or does it ignore the file? if it does how damaging can it be?

     
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    Feb 16, 2012 6:58 AM   in reply to Simon Full

    Hi Simon,

     

    If you are converting a lossy compressed DNG to another lossy compressed DNG of the same image dimensions (i.e., no downsampling), then there is no loss of quality.  This is because we recognize this special case and simply copy over the compressed data stream as-is (verbatim).  Thus, we do not decompress & recompress, which would lose quality. 

     

    Of course, if you are generating a lossy compressed DNG of another image size (e.g., going from 10 MP to 4 MP), then of course the image characteristics will change because the image is getting smaller ...  

     

    Eric

     
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    Feb 16, 2012 9:26 AM   in reply to MadManChan2000

    Thanks Eric, really like this whole lossy idea.

     
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