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A
adiscerningeye
Participant
August 31, 2017
Answered

How can I be sure that I am copying RAW to DNG into Lightroom without loss/lossy ?

  • August 31, 2017
  • 4 replies
  • 666 views

I take pictures using NEF (RAW) 24MP on a Nikon D750 using Nikon Lossless compression on the camera.  I then import them into Lightroom automatically converting them into DNG.

I realise that DNG compresses them further normally without any loss of quality. However my DNG files are only around 20MB and I'm how surprised how small they are compared to around the 50MB size originals on my camera.

I want to make absolutely sure that I am not compressing with any loss of information (notably lossy). Can anyone afdvise me how I can do this?

To be honest, this issue is putting me off converting to DNG altogether.  If I had simply been importing my RAW files simply as NEF files I wouldn't have this issue at all.

Thank you for your help.

    This topic has been closed for replies.
    Correct answer JP Hess

    I suppose you could ask yourself the same question about lossless compression in the NEF files. How do you REALLY know that you aren't losing some quality in the NEF compression? One way you could compare would be to import the NEF files and then convert them to DNG using Lightroom and retain the NEF files. Then you could compare the two side-by-side. Have fun doing so because you can spend hours trying to see any difference.

    4 replies

    A
    adiscerningeyeAuthor
    Participant
    September 1, 2017

    Thank you all for your replies.  I wanted to reply that you all answered correctly but I think that I can only do it once :-(

    I have also gone into the metadata and clicking the DNG drop down window I see that"Lossy Compression: no" which reassures me further.

    I'll be sticking with DNG then afterall.

    Thank you all for your help.

    Rob_Cullen
    Community Expert
    Rob_CullenCommunity Expert
    Community Expert
    September 1, 2017

    I have a D750. I convert to DNG at LR Import.

    My NEF files are 27.9 megaBytes.  LR shows them as 24.2 megaPixels

    As  DNG they are 21.1 megaBytes and LR shows them as 24.2 megaPixels.

    DNG files are 'raw' files. There is no loss of image sensor data whatsoever. They are identical as images.

    Only some proprietary metadata may be lost in conversion. ("fancy" camera features if the D750 has any?)

    My original NEF files are never, never have been, 50mB.

    Note: If you use the "Adobe DNG Converter", and select the option to embed the original file, then you will get a file that is twice the size.

    Regards. My System: Windows-11, Lightroom-Classic 15.3, Photoshop 27.5, ACR 18.3, Lightroom 9.3, Lr-iOS 10.4.0, Bridge 16.0.3 .
    A
    adiscerningeyeAuthor
    Participant
    September 1, 2017

    I wanted to reply that you all answered correctly but I think that I can only do it once :-(

    I have also gone into the metadata and clicking the DNG drop down window I see that"Lossy Compression: no" which reassures me further.

    I'll be sticking with DNG then afterall.

    Thank you for your help.

    Per Berntsen
    Community Expert
    Per BerntsenCommunity Expert
    Community Expert
    August 31, 2017

    Are you sure that the NEFs are 50 mb?

    The NEF files from my 24 megapixel D7100 are around 30 mb, and DNGs are around 25 mb. The file size for both formats will vary somewhat, depending on the image.

    This is not something I would worry about, but you can, like Jim suggested, compare them.

    Make sure to compare them at 1:1 magnification. I don't think you'll see any difference.

    A
    adiscerningeyeAuthor
    Participant
    September 1, 2017

    I wanted to reply that you all answered correctly but I think that I can only do it once :-(

    I have also gone into the metadata and clicking the DNG drop down window I see that"Lossy Compression: no" which reassures me further.

    I'll be sticking with DNG then afterall.

    Thank you for your help.

    JP Hess
    JP HessCorrect answer
    Inspiring
    August 31, 2017

    I suppose you could ask yourself the same question about lossless compression in the NEF files. How do you REALLY know that you aren't losing some quality in the NEF compression? One way you could compare would be to import the NEF files and then convert them to DNG using Lightroom and retain the NEF files. Then you could compare the two side-by-side. Have fun doing so because you can spend hours trying to see any difference.

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