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Thread: A850 raw's > DNG

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    A850 raw's > DNG

    Is there any downside to converting A850 raw's to Dng.

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    Re: A850 raw's > DNG

    Quote Originally Posted by barry685 View Post
    Is there any downside to converting A850 raw's to Dng.
    I don't have an A850, but the same is true of all DNG files created from native raw files:

    - DNG files are lossless with respect to the original native raw files, all the data in them is the same as what is in native raw files. They're simply organized differently, according to a publicly disclosed file format standard. This includes the manufacturers' potentially encrypted or private/non-disclosed components ... they're all in there.

    - IF the manufacturer of the camera has some encrypted or private components in the raw files, only the manufacturer's own software is going to read it. And most manufacturer's software doesn't read DNG files.

    - If you use Adobe software (Lightroom, Camera Raw, etc), any such manufacturer-only native raw file components are of no value anyway, the conversion to DNG produces functionally identically results to working with the native raw files.

    - Some non-Adobe image processing applications that support using DNG files are either incomplete or buggy in their handling of DNG format. (Aperture comes to mind here as a prime example.)

    The difference between using DNG vs native raw files is primarily a matter of file management and convenience at this time.. That is, the major benefit of using DNG files, particularly if you use Adobe software, is that DNG files allow additional metadata to be stored in the same file as the raw data rather than having to store it in auxiliary 'sidecar' files (.XMP) which must be kept together with the native raw file to preserve the additional metadata. DNG also uses a lossless compression algorithm that can save disk space over many native raw file formats.

    In the future, when there are so many different cameras and native raw file formats in existence, having files in DNG format might mean the difference between being able to process them with the latest software and/or having to keep an older system up and running with old software to process long-obsolete cameras and native raw file types. That day hasn't happened yet, but it will at some point due to the costs of testing new software for old, obsolete raw data files.

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    Re: A850 raw's > DNG

    Thanks
    I was concerned if there was any quality loss. In the case of a a850 raw, the file size is less than 1/2 the original raw.

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    Re: A850 raw's > DNG

    DNG may not be exactly archival, if you want to get deep into it: http://www.libraw.org/articles/2-ways-to-nowhere.html

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    Re: A850 raw's > DNG

    Quote Originally Posted by barry685 View Post
    Thanks
    I was concerned if there was any quality loss. In the case of a a850 raw, the file size is less than 1/2 the original raw.
    Processing my image files in Lightroom or Camera Raw, whether I use a native raw or a DNG file from any of my cameras produces exactly the same results with the same parameter settings.

    The best thing to do is to test with the application software you are intending to use, but I'm pretty confident that Lightroom and Camera Raw will do everything very well. Other applications might differ.

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    Re: A850 raw's > DNG

    Quote Originally Posted by douglasf13 View Post
    DNG may not be exactly archival, if you want to get deep into it: http://www.libraw.org/articles/2-ways-to-nowhere.html
    Looks like another Open Source advocacy page. LibRaw ... who the heck is that? Their "About LibRaw" page doesn't say anything about who "iexa" is.

    Most of the statements made about DNG aren't well researched.

    Digital data can't be archival anyway. Archival has to do with the capability of a medium to persist through time without degradation. Digital data isn't a medium, it is stored on a medium. ;-)

    I see articles like this pop up from time to time. Most are a waste of time. The practical reality is that the Adobe Digital Negative specification is as good as has happened for a standard raw camera data format to date, and nothing else has emerged that even comes close. We have either that or we live with native raw formats and whatever a manufacturer wants to offer.

    If you want an archival photograph, make a print ... on the right paper, with the right ink, and store it carefully.

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    Re: A850 raw's > DNG

    Do a search on here or PM Hardloaf for his views on why DNGs are bad. I've gone back and forth and for now I use native raw files for working and backup and DNG for archiving. Some things to keep in mind is that DNG is available online and available to anyone, but it is owned by Adobe. It is not an open standard, don't be confused about that. Further, Adobe is the only software that really seems to support DNG, but all software seem to support native raws.

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    Re: A850 raw's > DNG

    Quote Originally Posted by Bill_Green View Post
    Do a search on here or PM Hardloaf for his views on why DNGs are bad. I've gone back and forth and for now I use native raw files for working and backup and DNG for archiving. Some things to keep in mind is that DNG is available online and available to anyone, but it is owned by Adobe. It is not an open standard, don't be confused about that. Further, Adobe is the only software that really seems to support DNG, but all software seem to support native raws.
    DNG is a publicly disclosed standard, accessible to anyone with no license fees in perpetuity. Read the license on http://www.adobe.com/dng/ where you can also download the specifications. If that's not an "open" standard, what is? Even an Open Source project requires a statement and license.

    Adobe also owns the TIFF standard. Should we not use that either because it isn't "open"? ;-)

    I've read Hardloaf's views before. They're uninteresting to me, they reiterate what has been written dozens of times before on several other forums since the OpenRaw supporters decided to make dissing DNG an agenda item. OpenRaw hasn't produced anything worthwhile or usable.

    I use Adobe's software for my image processing, because it works better than anything else I've found, so I don't really care much if some other vendor's software doesn't support DNG. Lots of other software also supports DNG files, but several of those are incomplete (and/or buggy) implementations. It is certainly the case that not all the other software supports all the native raw file formats. I archive my original native raw files too ... in the five years or so I've been doing that, I've not once had any reason to go back to them due to a problem with a DNG file.

    This is a prickly realm full of personal opinions and politics. I stand by my responses to the OP, and don't care to make a debate out of raw standards or lacks thereof.

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    Re: A850 raw's > DNG

    You're tugging on Superman's cape a bit in regards to Andrey, Lexi and Iliah. You're talking about a few of the most prominent, knowledgeble leaders in the RAW development community.

    We can certainly discuss whether converting to DNG shows any practical difference, but the OP should know that there are issues with the "standard," and he can decide whether it matters or not.

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    Re: A850 raw's > DNG

    Quote Originally Posted by douglasf13 View Post
    You're tugging on Superman's cape a bit in regards to Andrey, Lexi and Iliah. You're talking about a few of the most prominent, knowledgeble leaders in the RAW development community.

    We can certainly discuss whether converting to DNG shows any practical difference, but the OP should know that there are issues with the "standard," and he can decide whether it matters or not.
    As I said, I choose not to debate the politics of this. I didn't find anything in that article, including the incorrect bits, that I haven't seen a dozen times before.

    That said: If the author of a thesis doesn't say who he is and why his statements might have some merit via his credentials, to me the thesis is ignorable. I have no idea who these "prominent, knowledgable leaders in the RAW development community" are, I've never heard of them before. And the website presents no information to change that.

    G

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    Re: A850 raw's > DNG

    There are no political points to debate, for me. Heck, I even use Adobe for raw conversion, myself. I'm more interested in the debate of the technical points.

    I'm a little surprised that you haven't heard of Alex or Iliah, but they make their email available at the end of every page on libraw.org, and they're usually glad to answer any questions you may have.

    FWIW, Iliah also codeveloped the rather well respected Raw Photo Processor.

  12. #12
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    Re: A850 raw's > DNG

    Quote Originally Posted by Godfrey View Post
    ...

    The difference between using DNG vs native raw files is primarily a matter of file management and convenience at this time.. That is, the major benefit of using DNG files, particularly if you use Adobe software, is that DNG files allow additional metadata to be stored in the same file as the raw data rather than having to store it in auxiliary 'sidecar' files (.XMP) which must be kept together with the native raw file to preserve the additional metadata. DNG also uses a lossless compression algorithm that can save disk space over many native raw file formats.

    In the future, when there are so many different cameras and native raw file formats in existence, having files in DNG format might mean the difference between being able to process them with the latest software and/or having to keep an older system up and running with old software to process long-obsolete cameras and native raw file types. That day hasn't happened yet, but it will at some point due to the costs of testing new software for old, obsolete raw data files.
    A quick note on you're two last points:

    - I find it a big advantage that the RAW files doesn't change. Those are backupped by my and verified (with checksum) very early in the workflow. (Actually not fast enough for my taste, but that's a tradeoff for me) Those RAWfiles won't change anymore, that's important. The metadata sidecars are very small and don't give any volume problems, storing 20or 100 backups is a non issue.

    - The last point is a strange one. The decoding of the RAWfile is the easy part for a RAW converter, especially because the sourcecode for dcraw is public available (It's difficult for brand new camera's, but not for existing). The most work is getting the needed test images and calibration info for the camera, this is difficult to do with an obsolete camera. So it will be the camera that will give problems, not the RAW format.

    One from me : don't expect you're new (version of) raw converter to render the images exactly the same. IMHO it's needed to keep a "developed" copy and 16-bit tiff profoto RGB no layers is a nice format for it. (tiff can be zipped internally to save place)

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    Re: A850 raw's > DNG

    Quote Originally Posted by Godfrey View Post
    ... I archive my original native raw files too ... in the five years or so I've been doing that, I've not once had any reason to go back to them due to a problem with a DNG file.

    This is a prickly realm full of personal opinions and politics. I stand by my responses to the OP, and don't care to make a debate out of raw standards or lacks thereof.
    Ok, you archive the original RAW's and DNG's, that's prudent. Archival is something we rather don't need, just like insurance. I also go seldom back, but it was very usefull a few times...

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    Re: A850 raw's > DNG

    Quote Originally Posted by alainD View Post
    - I find it a big advantage that the RAW files doesn't change. Those are backupped by my and verified (with checksum) very early in the workflow. (Actually not fast enough for my taste, but that's a tradeoff for me) Those RAWfiles won't change anymore, that's important. The metadata sidecars are very small and don't give any volume problems, storing 20or 100 backups is a non issue.
    Others have made this assertion. I suspect it depends on how you manage and work with image files, what your needs are. If you move files around frequently and in large volumes (think of a motion picture post-production workflow), having all the metadata encapsulated in the DNG is a plus as there are far less chances for the .XMP sidecar to be lost and/or corrupted. If you tend to have a pretty static workflow ... the file repository is written to and left in place most of the time ... the benefit of encapsulating additional metadata is reduced and the .XMP files pose a smaller burden on incremental update strategies.

    Of course, if your workflow is Lightroom to exported products, with potential round trip to Photoshop during image editing as RGB file, then it doesn't matter much. DNG or native raw can be completely static, there's no need to output .XMP sidecar files unless you also need to work in Bridge and Camera Raw for some other reason.

    Similar with Aperture and perhaps even moreso: you can choose to use the Aperture library file as the image file respository and let Aperture take care of everything. No sidecar files, just the big .aplibrary files containing everything ... export what you want from it.

    Quote Originally Posted by alainD View Post
    - The last point is a strange one. The decoding of the RAW file is the easy part for a RAW converter, especially because the sourcecode for dcraw is public available (It's difficult for brand new camera's, but not for existing). The most work is getting the needed test images and calibration info for the camera, this is difficult to do with an obsolete camera. So it will be the camera that will give problems, not the RAW format.
    It's not the decode or changes to the decode that get expensive. It's maintaining and adding to an ever increasing number of test cases in the QA cycle to be sure that you haven't broken something in incremental revisions of the raw processing engine that become costly over time. On a case by case basis there isn't a huge burden, but when you start planning to do a rev and realize that you need to run a test case for 100,200, 400, 1000 different kinds of raw files that this starts to absorb a LOT of time and resources.

    Quote Originally Posted by alainD View Post
    One from me : don't expect you're new (version of) raw converter to render the images exactly the same. IMHO it's needed to keep a "developed" copy and 16-bit tiff profoto RGB no layers is a nice format for it. (tiff can be zipped internally to save place)
    ABSOLUTELY! A raw converter is an interpreter, image rendering will shift as that interpreter is changed. I output a ProPhoto RGB, 16-bit per component flat TIFF file for every "finished" photo I produce and add it to my project archives independent of the original image files. Much less chance of a TIFF file's rendering shifting due to the underlying display software.

  15. #15
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    Re: A850 raw's > DNG

    Quote Originally Posted by Godfrey View Post
    ...

    It's not the decode or changes to the decode that get expensive. It's maintaining and adding to an ever increasing number of test cases in the QA cycle to be sure that you haven't broken something in incremental revisions of the raw processing engine that become costly over time. On a case by case basis there isn't a huge burden, but when you start planning to do a rev and realize that you need to run a test case for 100,200, 400, 1000 different kinds of raw files that this starts to absorb a LOT of time and resources.
    ...
    The decoding of the RAW file is an easy test and should be automated. There's a known input (the RAW files) and a known output (a memory image that contains the decoded "file" after the decoding proces but before further steps or a hash from it). Regression testing this is trivial.

    The step after that which manipulate the image to get a good results are another matter and those depend on the camera. If the pipeline changes all those needed to be tested... But this is not depended on the filetype (original or DNG), but on the camera. If different test images are needed, those have to be made. (Think changing the it-8 target to another one or shooting with more color temperatures.)

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