6 Replies Latest reply on Nov 11, 2008 8:47 AM by Greg Barnett

    "Preserve Raw Image" DNG really portable?

    Level 1
      I've tried to get a response on this before and haven't quite been able to get one that seems totally clear.

      Here's the thing - one of the big selling point about DNG is that if you convert your RAW images to DNG, in 10 years when no one is making a RAW converter that supports your ancient camera, by being converted to DNG you'll still have options.

      Well, I'm wondering unless you set "Convert to Linear Image" if that's really true?

      I base this question on the fact that I shoot Fuji cameras and I've run into multiple converters who while handing DNG do not in fact handle DNG from Fuji cameras. For instance Capture One while handing DNG for other cameras specifically does not handle it for the Fuji S3 and S5. The old RAW Shooter handled DNG but would never handle DNGs from the Fuji S2.

      The reason I believe is because by default the image remains in "mosaiced" form in the DNG. Meaning that it's the unaltered proprietary RAW data as it was taken off the sensor, in turn meaning that it's the same data found in the vendors own RAW formats, in turn meaning that in 10 years a RAW converter trying to read it ultimately needs to understand the propriety mosaic format of the camera manufacturer. In short, it would be no more portable than a RAW file unconverted from the vendor.

      Yes, if it was converted to "linear" it would be portable, but if it's converted to "linear" you've fixed it in stone and really it doesn't have much difference from say converting it to TIFF (particularly since DNG is based on TIFF right?).

      Anyway, this isn't a huge deal to me. The advantages relating to compression and metadata make it compelling for some uses, however there are a lot of people out there saying, "Convert it to DNG for maximum long term compatibility," and they're not suggesting to use linear form. For instance the otherwise excellent, "The DAM Book".

      Am I incorrect? I'd love to hear I'm missing something because it's compelling in many other ways.

      Thanks.
        • 1. Re: "Preserve Raw Image" DNG really portable?
          Level 1
          > "The reason I believe is because by default the image remains in "mosaiced" form in the DNG. Meaning that it's the unaltered proprietary RAW data as it was taken off the sensor, in turn meaning that it's the same data found in the vendors own RAW formats, in turn meaning that in 10 years a RAW converter trying to read it ultimately needs to understand the propriety mosaic format of the camera manufacturer. In short, it would be no more portable than a RAW file unconverted from the vendor."

          It IS more portable. It could be processed by any product that accepted DNG's "staggered" metadata, and that software would be able to handle any cameras that used a staggered configuration:
          http://www.barrypearson.co.uk/articles/dng/specification.htm#fujifilm

          Currently, this only applies to Fujifilm cameras. That isn't a DNG restriction, but just the nature of the industry.

          DNG doesn't require the software accepting the DNG file to recognise specific Fujifilm models, "just" to recognise the tags that define the staggered configuration. Many software products don't, and again that isn't a DNG restriction, but (presumably) the result of business decisions by the software suppliers.

          DNG can't remove the need for raw-processing software to have algorithms suitable for the sensor configuration concerned. Neither can Adobe force other companies to implement the whole of the DNG specification. In future, to use the software you want, you may either have to persuade them to add support for this feature of DNG, or convert those non-linear DNGs to linear-DNGs.
          • 2. Re: "Preserve Raw Image" DNG really portable?
            ArrrBee Level 1
            I put no faith of any kind on other companies to support DNG 20 seconds from
            now let alone 10 years from how. It is interesting that you are worried
            about these other problems and not so worried about whether anything will be
            able to open the DNG file. The point of the future proof DNG is not will
            every raw processor on the market in 10 years be able to open it. You can't
            do that now. The question is will any raw processor be able to open them and
            the answer is Adobe will. Having one company who's products can open any DNG
            file is better and a lot more future proof than no company which is what
            could happen with a proritary raw format. Also given that DNG is pretty much
            a free format available to anyone there are going to be other options as
            well. Maybe not from the big raw processor makers but shareware and so on.

            I don't think DNG will go the way of PhotoCD or some of Kodak's old formats
            that are pretty much unsupport even by Kodak. In the end however there is no
            guarantee and the fact that some raw processor makers choose to only support
            DNG for some cameras and those cameras that have to support the propritary
            formats before they support DNG sucks and everyone should be complaining to
            them to stop that sh*t.

            I convert all of my images to DNG and have faith in Adobe and DNG is far
            more future proof than any other raw format.

            Robert
            • 3. Re: "Preserve Raw Image" DNG really portable?
              Level 1
              I guess I feel like DNG has gotten enough acceptance, even if it's not as fully implemented as it could but, that I have relative confidence that it will be supported in the long term.

              It's true that at the very least Adobe will support DNG moving forward, but because all these models are already baked into ACR outside of DNG (for instance, ACR supports S2 RAF, S3 RAF, S5 RAF etc.) that I also trust Adobe to support the unconverted RAW formats as well for the long term. In short, I'm not sure it's any less likely that Adobe won't support Fuji RAF in 10 years than Fuji RAF converted to DNG.

              Regardless, the issue here as I see it is many well informed people are indicating with no qualification to convert to DNG for long term portability, but for some models at least this isn't really any more portable (and perhaps less) than the original format.

              Thanks to Barry I guess I see why it's "technically" more portable - it isn't being literally encoded in the same RAW format as came out of the camera, but unfortunately not all RAW converters are supporting the total DNG spec. In that regards I guess it's neither here nor there, but ultimately it doesn't matter to me because the fact is these other converters aren't working for me.

              That in turn is a shame, because while I trust Adobe to be there in the future for me and I use Lightroom more than any other converter, I still find Capture One and DxO as very nice converters that have advantages in some cases over Lightroom.

              Thanks Barry and Robert for your replies!
              • 4. Re: "Preserve Raw Image" DNG really portable?
                Thomas Knoll Level 2
                >Yes, if it was converted to "linear" it would be portable, but if it's converted to "linear" you've fixed it in stone and really it doesn't have much difference from say converting it to TIFF (particularly since DNG is based on TIFF right?).

                Actually, this is not true.

                A linear DNG created from a raw file still has nearly all the flexibility advantages of a "mosaic" raw file. It is still trivial to change white balance, exposure adjustments with full highlight recovery, use different camera profiles, etc. The only thing you lose the ability to use newer demosaic algorithms in the future.

                TIFF files are much harder to adjust because the white balance and exact exposure setting have already been "burned into" the image data.
                • 5. Re: "Preserve Raw Image" DNG really portable?
                  Level 1
                  Thanks Thomas - that's very useful to know!
                  • 6. Re: "Preserve Raw Image" DNG really portable?
                    Greg Barnett Level 2
                    Yes many thanks for that explanation. I was under the incorrect impression that linear files were much more limited in their ability to withstand significant adjustments.