Preservation of photographs - DNG vs Raw

Discussion in 'Digital Photography' started by InfiniteLoopy, Sep 15, 2013.


Do/will you preserve your original camera files as Raw or DNG?

  1. Raw (.cr2, .nef)

    11 vote(s)
  2. DNG

    5 vote(s)
  1. InfiniteLoopy macrumors 6502

    Dec 14, 2010
    I currently use a Canon DSLR and backup its CR2 files as well as Aperture-generated previews (JPEGS).

    I'm considering whether converting the CR2 files to digital negatives (DNG) would make more sense from an archival point of view. It seems that DNG is "open" and supported by many photography applications. Essentially, I wonder whether in 20-30 years time, CR2 will be a long-forgotten file format whereas DNG will be the archival standard for raw files.
    I'd be interested in opinions on RAW vs DNG and whether anyone knows what large organizations with an interest in preserving their digital photographs use as file format.
  2. acearchie macrumors 68040


    Jan 15, 2006
    I believe this statement is wrong:

    DNG is a raw image format and is lossless in the same way that .Cr2 is a raw format and is lossless.

    At this point it's a gamble knowing which one will survive the longest. Given that it was created by Adobe you would assume that their software would continue to support it but who knows how long they will last!

    I see JPEGs being supported for a long time so I see no harm in exporting finished edits as a high quality JPEG as well as keeping the raw files.
  3. InTheMist macrumors member


    Jun 22, 2013
    I convert to DNG for compatibility reasons. That said, my faith in Adobe has been shaken due to recent business decisions, so I'm worried about the future of the format. As 'Loopy said, you can always export to JPEG (or TIFF) from DNG if compatibility ever becomes an issue in the future.
  4. throttlemeister macrumors 6502a

    Mar 31, 2009
    DNG is submitted for inclusion in the ISO12234-2 standard. There is no logical reason to worry about the future of the format, and there is no reason to believe Adobe will drop support of DNG.
  5. InfiniteLoopy thread starter macrumors 6502

    Dec 14, 2010
    Thanks for the replies.
    Does anyone know when the ISO standard is likely to be approved?
    I'm considering converting my .CR2 to .DNG, which I understand has the advantages of being equally as lossless, seemingly open and takes up less space, which is useful for backups. Are there any disadvantages in doing so, except that I'd have to run the CR2s through the converter before importing into Aperture?

    I wonder if storing DNGs is the "done thing" in the photography archival world...?
  6. ChrisA, Sep 15, 2013
    Last edited: Sep 15, 2013

    ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    What you are saying is that the software needed to read CR2 files will disappear before the software needed to read DNG files. I seriously doubt that. There are so many Canon cameras in the world and so few people are using DNG that I think CR2 has the better chance of surviving.

    You can wait and see. n 20 years if CR2 is looking like it might fad away, convert your images at that time. Likely them DNG will seem like a silly format because something better is available. There is no reason to start the process years in advance

    I think you might loose data in the CR2-> DNG conversion. You loose the camera setting, like which AF sensor was used to focus the image and so other things that are specific to Canon. I know this info is lost when you convert Nikon NEF files.

    But neither CR2, NEF or DNG is an image file. They are camera formats. If you want to preserve an image store it as either a TIFF or JPG.

    The far more importent question is backup. How are you backing up your filers If you want a 99% chance they will last for 25 or more years then you need to make sure you always have the images stored on three different media in at least two geographical locations. You will also need to rotate the media the backups are stored on and frequently test the backup media. That is a bare minimum. Do more if you want them to last 100 years.

    But you know what? As you shoot more and more images fewer of them remain important. You need to go back and cull out the worst ones. Removing the weakest images has the effect of making the over all collection stronger. In other words it is good to periodically trash some old photos.

    But keeping the good ones backed up is hard. You need a minimum of four disk drives to allow for rotation to an off site location.

    Then there is the problem of cataloging the images. Even if the file format is the current trendy thing and you still have multiple backups if you can't find a photo out of the 50,000 files you have it may as well be lost to a disk failure. So what cataloging system will you use that you know will still work in 25 or 50 years? I'd say there are no good options. All you can do is periodically switch to whatever is best and upgrade and actively maintain the collection moving it from system to system every 5 to 10 years.

    Don't put much trust in ISO standard formats. I have some magnetic tale reels that are "standard" and punched cards are standardized years ago too. Standards come and go rather quickly.
  7. snberk103 macrumors 603

    Oct 22, 2007
    An Island in the Salish Sea
    Two other points. Well, one and half points.

    1) CR2 is a proprietary format. Canon is under no obligation to document the format of CR2 files for 3rd party developers. So there it is possible that you would like to use an application, but it does not support your camera because the developer doesn't have access to the CR2 documentation. This has happened to Capture One software in the past.

    On the other hand, Adobe has made the DNG spec public and anyone is welcome to support DNG files. The ISO application is to simply make this a formal arrangement.

    2) I believe that while multiple Canon cameras produce CR2 files - they are in fact different file formats internally (that simply share a dot-suffix). So, one Canon camera may be supported by an application - but not a different model since the file is internally different. And until Canon shares the documentation....


    Whether or not these considerations matter, only you can decide.

    Hope this helps.....
  8. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    This is likely the best specification for CR2

    But you are worrying about something that today makes zero difference. And if some day it does, then you can can convert in a few hours (I assume computers will be faster then)

    I guess we worry about the day they stop making tires to fit my car. Yes I suspect in 50 or 80 years they might be hard to find. I'll deal with the problem when it happens. Canon is not going to disappear tomorrow and even if they did your current software will continue to work for years, giving you time to deal with converting to whatever is popular at that time.
  9. snberk103 macrumors 603

    Oct 22, 2007
    An Island in the Salish Sea
    Like I said, only the OP can make that decision based on their circumstance. I was offering additional info so that they can make a more informed decision.

    Two other things, though.

    1) I am worried about file formats being supported today. I don't worry about them changing in the future. I am absolutely resigned to the likelihood that I will be converting all my photos at some point. It will be a chore, and you are right... it will be automated. I've been using computers for a long time and have seen several formats come and go. Formats that I used to use. However, because CR2 is a proprietary format.... there are applications today that may not support a particular Canon camera.

    For instance, Capture One occasionally bumps up against propriety RAW formats. When a new camera is introduced - if the RAW format is modified from the previous version - then until that camera manufacturer shares the documentation of the format folks using the software complain that their new cameras are not supported. And Capture One has to explain that until they get the documentation from the camera maker there is nothing that they can do.

    This can be a problem for any 3rd party developer. It may or may not be problem for you or the OP. Only you and the OP know what applications you use. Or are likely to use.

    2) With respect, I believe that your statement " few people are using DNG..." may not be quite on the mark. Lightroom is used by many many people, folks who are using Canon, Nikon, PhaseOne, Mamiya, Leica, Sony, Fuji, Konica-Minolta, Kodak, Lumix, Hasselblad, Ricoh, Olympus, Pentax, Casio, Contax, Samsung, Sigma, Leaf, and Epson cameras. Have I missed a few?

    Several of these camera makers can save direct to DNG rather than their own RAW format - and some use DNG as their native RAW format.

    The default format for Lightroom is DNG. So - with all those people using all those cameras above and using Lightroom I would guess/hypothesis/venture/opine that there are at least as many people using DNG as CR2- if not more.

    But that is just my personal opinion.
  10. phrehdd macrumors 68040


    Oct 25, 2008
    You can always later convert RAW files later as someone pointed out. If you feel that your RAW files is not requiring much work might consider TIFF as it is fairly universal. Those images that require lots of work require a decision if the original is what you want to keep or the corrected file only (or both).

    Candidly, I find no problem leaving images in original raw file format as it doesn't take much down the road to convert them. I would say that jpeg is NOT a really good option as it is lossy.
  11. throttlemeister macrumors 6502a

    Mar 31, 2009
    Lightroom, by default, does not touch raw files. I do convert my NEF files to DNG in Lightroom, but that's not because because of file format compatibility: DNG is slightly faster in LR, and I don't have to mess with sidecar files as LR stores any adjustments I make in the metadata of the DNG. So if my database ever gets corrupted, I can just create a new one and all my adjustments and history are right there.

    The downside of that of course is that if I modify files, all those big files will be backedup again.
  12. InfiniteLoopy thread starter macrumors 6502

    Dec 14, 2010
    I've added a poll to see what is most popular among forum users.

    I don't have a concern with my backup strategy: Everything to Time machine, hard drive cloned, and selects to the cloud.

    I don't think this analogy works as you most likely won't be driving the same car in 50-80 years, however you will want camera files made today to be viewable in that time frame.

    But TIFFs take up more space than RAW or DNG files.

    Today I shoot Canon, but tomorrow I may shoot something else (I'm interested in the Fujis). I wonder if having a uniform archival format would be beneficial in the long run.

    Another question: If I do convert CR2 to DNG before opening in Aperture, will I be using Adobe's or Apple's raw converter?
  13. snberk103 macrumors 603

    Oct 22, 2007
    An Island in the Salish Sea
    Fair enough. It would have been accurate for me to say that Lightroom by default asks if you would like to convert your RAW files to DNG initially. But of course it will happily work with the proprietary RAW files after that.

    The point I was trying to make was simply that with all those different camera's RAW files potentially being converted to DNG - there will be more than just a "few" people using DNG... which was ChrisA's contention.
  14. ocabj macrumors 6502a


    Jul 2, 2009
    The only time I have converted from Canon RAW (.cr2) to DNG was when I was running a version of PS that didn't support my camera and that window of time was very short (update to PS was released).

    Anyway, I do not convert from Canon RAW to DNG simply because the CR2 file is the native file written by the camera. I have no idea if the DNG conversion is retaining every singe piece of data recorded in the CR2.

    To me, converting from Canon RAW to DNG is suspect in that you're gambling on how the DNG conversion utility is interpreting the RAW file. Notice how Adobe updates their Camera RAW engine not just for camera support but also to improve how the engine interprets data. It's quite possible Adobe will change the DNG specifications and update the DNG conversion utilities which read the source RAW file differently. If that happens, do you reconvert every single RAW file from your camera with the new DNG utility/specification?

    DNG makes the best sense if the camera itself actually records to DNG natively (in-camera). If Canon and Nikon did this, I think this would be ideal. But odds are highly unlikely either company will do this.

    Keeping the original native raw file recorded by the camera, whether it be Canon RAW, Nikon RAW, or DNG, is the best way to preserve the 'original' data.
  15. Razeus macrumors 603

    Jul 11, 2008
    Whatever the camera's native RAW file is. DNG is a RAW file, especially if you're on Leica. What I don't condone is "converting" your camera's RAW file to a DNG file. DNG is NOT the original file from your camera.

    Always keep your original RAW's. If necessary down the line, make a copy and convert THE COPY to a DNG.

    Otherwise, DNG is a dead file format quite frankly (unless your camera natively generates them).
  16. bocomo macrumors 6502

    Jun 29, 2007
    New York
    it's not just about a company "disappearing" but with changes to the file format and 3rd party programs (as stated above)

    Canon raw files used to be .CRW, then changed to .CR2 and with several flavors of that one

    i convert all my .CR2s to DNGs so that i don't have to deal with sidecar files, have greater 3rd party compatibility, smaller file size
  17. r.harris1, Sep 16, 2013
    Last edited: Sep 16, 2013

    r.harris1 macrumors 6502a


    Feb 20, 2012
    Denver, Colorado, USA
    I've never seen a compelling reason to convert my RAW files to DNG so I don't. Most of the tools I use support both my camera's RAW format and the tool's implementation of the DNG spec. DxO and Bibble/ASP had some issues associated with converted DNG so from my perspective, I still have somewhat more control with RAW.

    If I need to in the future, maybe, but don't see it in any near or even medium term tea leaves.

    Postscript: I should add that I'd love to see an accepted RAW standard adopted by all of the manufacturers and don't see why DNG shouldn't be that standard. It's not yet, though, and I suspect that it will be a long time in coming, if ever.
  18. BJMRamage macrumors 68020


    Oct 2, 2007
    I am VERY new to RAW shooting and have been reading up on things but I read somewhere, recently, that you should be fine to keep things in your Camera-RAW format rather than converting/shifting to DNG.

    The idea was if there comes a day when your Camera-RAW will be discontinued, you will have time in advance to make a conversion then. Perhaps there will be an update to the DNG or a new/improved DNG or other RAW format down the road and at which time had you converted over to DNG now you might need to re-convert. thus doubling the conversion.

    When Floppies were pushed out of existence you had ample time to make the switch....and I know my ZIP disks contents are "lost" but that is not a worry for me now. I had time to make a switch but didn't feel the need. had I switched them to CD-R or CD-RW I'd still have them but not the need.

    ANYWAY, long story short (if still reading) is that the Camera-RAW should be fine and if a day comes when it will be phased out, you will have time then to make the conversion to DNG or whatever format is the going trend at that point.

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