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Thread: What is the difference between these DNG files (apart from their size on disk)?

  1. #1

    What is the difference between these DNG files (apart from their size on disk)?

    This was scanned from a photograph using Vuescan pro. The DNG is labelled muchBigger (50 MB) the other file (big) was obtained from it by opening in Photoshop Elements camera Raw 7.3 and alt-save on the save button. Please could you explain why the large size difference, and where I could have found out the information?
    muchBigger:
    http://sdrv.ms/16aXDNL

    big:
    http://sdrv.ms/16aXnhL

  2. #2

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    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by thisisamuchlongername View Post
    This was scanned from a photograph using Vuescan pro. The DNG is labelled muchBigger (50 MB) the other file (big) was obtained from it by opening in Photoshop Elements camera Raw 7.3 and alt-save on the save button. Please could you explain why the large size difference, and where I could have found out the information?
    muchBigger:
    http://sdrv.ms/16aXDNL

    big:
    http://sdrv.ms/16aXnhL
    I would be interested in comments re: the potential advantages, if any, of editing a DNG verus a TIFF file, from a scan? I currently have a workshop student who scanned with an Epson V700 and saved the files in DNG, now opens and edits them in Camera RAW. I can not find any advantage compared to my work flow, which is to save files in TIFF and work directly on them in PS. But she appears to have invested a lot of time in learning her method and seems fairly convinced that editing the DNG files with Camera RAW that gives better results than my method?

    BTW, the scans are of B&W negatives so no color issues are involved.

    Sandy
    http://www.sandykingphotography.com/
    For discussion and information about carbon transfer please visit the carbon group at groups.io
    [url]https://groups.io/g/carbon

  3. #3

    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by sanking View Post
    I would be interested in comments re: the potential advantages, if any, of editing a DNG verus a TIFF file, from a scan? I currently have a workshop student who scanned with an Epson V700 and saved the files in DNG, now opens and edits them in Camera RAW. I can not find any advantage compared to my work flow, which is to save files in TIFF and work directly on them in PS. But she appears to have invested a lot of time in learning her method and seems fairly convinced that editing the DNG files with Camera RAW that gives better results than my method?

    BTW, the scans are of B&W negatives so no color issues are involved.

    Sandy
    What does any of this have to do with the post? This appears to be totally unrelated.

  4. #4
    bdkphoto
    Guest

    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by sanking View Post
    I would be interested in comments re: the potential advantages, if any, of editing a DNG verus a TIFF file, from a scan? I currently have a workshop student who scanned with an Epson V700 and saved the files in DNG, now opens and edits them in Camera RAW. I can not find any advantage compared to my work flow, which is to save files in TIFF and work directly on them in PS. But she appears to have invested a lot of time in learning her method and seems fairly convinced that editing the DNG files with Camera RAW that gives better results than my method?

    BTW, the scans are of B&W negatives so no color issues are involved.

    Sandy
    My understanding is that the file from the scanner is not a true raw file, so there is no real advantage saving the file as a dng. Working in ACR, or Lightroom is an advantage over Photoshop as both are parametric image editors and offer non-destructive workflow even with tif files (there is still much more advantage with a true camera raw file). With ACR or Lightroom you are only changing the instruction sets to the file, not the file itself. In PS when you are working on a file you are doing pixel based changes to the file. Bottom line is that with ACR or LR you never change the state of the original file, in PS once you save the edits you've "fixed" the file in a new state.

  5. #5
    bdkphoto
    Guest

    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by thisisamuchlongername View Post
    This was scanned from a photograph using Vuescan pro. The DNG is labelled muchBigger (50 MB) the other file (big) was obtained from it by opening in Photoshop Elements camera Raw 7.3 and alt-save on the save button. Please could you explain why the large size difference, and where I could have found out the information?
    muchBigger:
    http://sdrv.ms/16aXDNL

    big:
    http://sdrv.ms/16aXnhL
    Check your output settings on camera raw. Are they 16 bit? You have file size parameters as well.

  6. #6
    Peter
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    Morro Bay, Ca
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    Re: What is the difference between these DNG files (apart from their size on disk)?

    Do you have "RAW compression" set? This is from the VueScan manual ...
    "Output | Raw compression
    (Professional Edition only)
    This specifies whether to use compression when writing the raw file.
    Compression of the raw TIFF file will not cause any loss of image data. It will take a little longer to read, and especially write, as the algorithm is computationally intensive, but can reduce total file size by as much as 40%.
    The default setting is "Auto", which enables compression for files with 12 or fewer bits per sample and disables compression for files using more bits per sample.
    Advanced Option: This option is displayed when Output | Raw file is set and when Output | Raw DNG format isn't set.

    Output | Raw DNG format
    (Professional Edition only)
    This specifies whether to write raw files in DNG (Digital Negative) format. This allows VueScan's raw files to be read by the Adobe Camera Raw plugin or other programs that read DNG files.
    These DNG format raw files can also be read by VueScan when you set Input | Source to "File".
    Advanced Option: This option is displayed when Output | Raw file is set."

  7. #7

    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by Peter Mounier View Post
    Do you have "RAW compression" set? This is from the VueScan manual ...
    "Output | Raw compression
    (Professional Edition only)
    This specifies whether to use compression when writing the raw file.
    Compression of the raw TIFF file will not cause any loss of image data. It will take a little longer to read, and especially write, as the algorithm is computationally intensive, but can reduce total file size by as much as 40%.
    The default setting is "Auto", which enables compression for files with 12 or fewer bits per sample and disables compression for files using more bits per sample.
    Advanced Option: This option is displayed when Output | Raw file is set and when Output | Raw DNG format isn't set.

    Output | Raw DNG format
    (Professional Edition only)
    This specifies whether to write raw files in DNG (Digital Negative) format. This allows VueScan's raw files to be read by the Adobe Camera Raw plugin or other programs that read DNG files.
    These DNG format raw files can also be read by VueScan when you set Input | Source to "File".
    Advanced Option: This option is displayed when Output | Raw file is set."
    If I understand you correctly, you suspect that the vuescan did not compress the files because I have it to save at greater than 12 bits/sample. And that when I save under camera-raw in PS Elements it is compressing the file, is that correct? In simple words, how can I check this?

  8. #8
    Peter
    Join Date
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    Re: What is the difference between these DNG files (apart from their size on disk)?

    In the VueScan application, under the Output tab. You can check "RAW compression" as a way to save the file. It is a lossless compression and can result in up to 40% smaller files compared to not compressing it. I can tell you where in the manual I found this. Open up VueScan and go to the help menu, or the user guide: User guide > Appendix A: Advanced tools and techniques > Using Raw scan files. That option is only available in the "professional" version of VueScan.

  9. #9

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    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by thisisamuchlongername View Post
    What does any of this have to do with the post? This appears to be totally unrelated.
    Perhaps the question does not seem not related to you. But my question is, why save a scanned file as DNG at all? What is gained by the extra size compared to saving the file as a TIFF? I seem to be missing something about all of this but I have a fair amount of experience with scanners and just don't see the point of DNG, especially since it adds so much size to a file compared to a TIFF.

    Sandy
    Last edited by sanking; 7-Mar-2013 at 14:27.
    http://www.sandykingphotography.com/
    For discussion and information about carbon transfer please visit the carbon group at groups.io
    [url]https://groups.io/g/carbon

  10. #10

    Join Date
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    Re: What is the difference between these DNG files (apart from their size on disk)?

    Quote Originally Posted by sanking View Post
    Perhaps the question does not seem not related to you. But my question is, why save a scanned file as DNG at all? What is gained by the extra size compared to saving the file as a TIFF? I seem to be missing something about all of this but I have a fair amount of experience with scanners and just don't see the point of DNG, especially since it adds so much size to a file compared to a TIFF.

    Sandy
    Sandy, I think the viewscan Raw files are saved with a linear curve (gamma = 1.0). I don't know how she's generating the DNG files, but I imagine they are also linear. There could be some advantage to this as you would only need to apply a gamma curve once. But I doubt it would be visible.

    However, my guess is she likes the camera raw interface. I honestly prefer it to Photoshop, at least for RAW files from the Nikon. Never tried it from a scan.

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