7 Replies Latest reply on Oct 21, 2015 1:14 PM by johnrellis

    DNG thumbnails on export

    bogiesan Level 4

      Searched first but found no direct assistance.


      We shoot NEF, Nikon's raw format, and import our photographs into Lightroom CC as NEF. After deleting the junk, we make changes in the Develop module before exporting as DNGs. We then import the DNGs into our enterprise digital asset management system, Canto Cumulus. Problem I've got is that Lightroom's DNG thumbnail references the original NEF, not the changes made in Develop. So our cCumulus catalog contains useless thumbnails. To get an idea of what the image actually looks like, our users must use a kludgy workaround and actually open the DNGs over the network into their local copy of Photoshop.


      Is it possible to force Lightroom to generate an accurate reference thumbnail that reflects changes made to our raw images?



        • 1. Re: DNG thumbnails on export
          99jon Adobe Community Professional & MVP

          Have you tried the metadata update before export?



          Metadata >> Update DNG Previews & Metadata


          I'm not sure third party apps can read it, but it's worth a try.

          • 2. Re: DNG thumbnails on export
            bogiesan Level 4

            Cool, non-intuitive but I'll try that!

            Back in a minute.

            • 3. Re: DNG thumbnails on export
              bogiesan Level 4

              That option is grayed out, unavailable, probably since I'm working with the NEF. A DNG image is not actually available until after the export is performed.

              If we must copy our NEFs to DNG upon import, that would change our processes tremendously around here. But it's possible.

              I'm trying the only metadata option I have for NEFs, "Save metadata to file."

              back in a minute.

              • 4. Re: DNG thumbnails on export
                bogiesan Level 4

                No good.

                I'll try importing a DNG.

                And that did not work either.

                I exported the NEF as a DNG with some develop changes.

                I imported the DNG into Lightroom and used Metadata: UpdateDNG preview and metadata.

                Exported as DNG.

                Imported into Cumulus but Cumulus only sees the original, unprocessed image without any Develop changes applied.


                Rats. But thank you for the suggestion! I'll keep working on it.

                • 5. Re: DNG thumbnails on export
                  bogiesan Level 4

                  So I'm stuck here: Lightroom creates a lovely thumbnail upon export to DNG that the MacOS sees and references for icon view in Finder. If I use QuickLook, however, the Mac looks at the original, unprocessed image, which is what I'd expect since quickLook has no raw handling capability. I'm trying to figure out a way to force Canto Cumulus to reference the thumbnail proved by Lightroom instead of creating its own from the source file.


                  Thank you again for your suggestion.

                  • 6. Re: DNG thumbnails on export
                    bogiesan Level 4

                    We are still having this problem with Canto Cumulus's importer. The advice I've been getting form Canto and from our tech support contractor is all wrong; apparently they understand databases but no one at either company really understands photography or Adobe products.


                    I have been told by Canto that Cumulus does not parse the XMP or ACR text data from either the sidecar or that is written back to the file. Yet we have tens of thousands of DNG files already in Cumulus that all have beautiful thumbnails that accurately reflect ACR edits, crops, and adjustments that were made in (previous versions of) Lightroom and imported into (previous versions of) Cumulus.


                    On our most recent interchange with tech support, we were advised to export as DNG from Lightroom, open the DNG in Photoshop, and resave out of Photoshop as DNG. Silly workaround but I was willing to try it. There is no "save as DNG" option in Photoshop CC that I can find. 

                    • 7. Re: DNG thumbnails on export
                      johnrellis Most Valuable Participant

                      It sounds like the problem is entirely on Cumulus's side. In LR CC 2015.1.1, I just exported a developed raw file as DNG with the option Embed Fast Load Data unchecked and JPEG Preview: Full Size.  I used the "dng_validate" command-line tool that ships with the Adobe DNG SDK (free to download), and observed three JPEG previews embedded in the DNG:


                      NewSubFileType: Preview Image

                      ImageWidth: 256

                      ImageLength: 171

                      BitsPerSample: 8 8 8

                      Compression: Uncompressed


                      NewSubFileType: Preview Image

                      ImageWidth: 1024

                      ImageLength: 683

                      BitsPerSample: 8 8 8

                      Compression: JPEG


                      NewSubFileType: Preview Image

                      ImageWidth: 5472

                      ImageLength: 3648

                      BitsPerSample: 8 8 8

                      Compression: JPEG


                      The Finder uses these preview images to display thumbnails that include the develop settings.  Interestingly, when you type space in the Finder to do a full-size preview via Quick Look, you get the image without the develop settings, which indicates that Quick Look is not using the embedded full-size preview image but is rather reading the main raw image. (And as you note, Quick Look doesn't know how to apply the LR develop settings encoded in the XMP metadata.)  Quick Look should use the embedded full-size JPEG preview if it is present.


                      So perhaps Cumulus is ignoring the embedded preview images entirely.