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DNG - Metadata sync with Capture One
dennis:
Hey Odd,
Thanks for your input! You are correct that the DNG spec (1.4) does say "metadata may be embedded" (and also correct about it being an option to embed original RAW file).
I wanted to see how Photoshop handles this (since Adobe is the creator of that as well as DNG and XMP). So I took a Leica M10 DNG file and "borrowed" an XMP file from a different photo (from an ARW). Totally different metadata in DNG versus XMP sidecar. I also made sure that the XMP sidecar file has a more recent modification time than the DNG file. Then I opened the DNG file into PS (via ACR plug-in). Guess what happens?
ACR uses the XMP metadata for the image loaded into PS (as we would hope), but then it also modified the DNG file to include this updated XMP, and then it deleted the XMP sidecar file! So I could (jokingly) say that there is your fix for transferring XMP sidecar metadata from C1 into DNG so PM can read it: open the photo in Photoshop ;) Obviously this is not a solution.
If the DNG has a more recent modification date, then the XMP sidecar is ignored as far as what metadata is loaded into PS. But PS/ACR still deletes the XMP sidecar!
This has a very unfortunate side effect if I put the DNG file (without an XMP sidecar) next to the ARW file (with an XMP sidecar), then make them have the same name, like this:
sample.DNG
sample.ARW *-| These belong together
sample.XMP *-|
Guess what happens? My ARW file now has no metadata after I open the DNG into PS/ACR, and if the ARW+XMP was more recently updated, then the DNG inherits the XMP of the wrong file. Not good!
A similar issue could happen in PM if we associate XMP sidecars with DNG. PM would have to figure out somehow whether the XMP belongs to the ARW or the DNG. If it chose (incorrectly) the DNG, and I moved or deleted the DNG, then the ARW file would lose its metadata (and of course the DNG would have the wrong metadata).
So, although the DNG specification says that you may embed XMP metadata, I think the expectation is that you embed the XMP instead.
We certainly are NOT going to make any changes to PM 5, but we may do something about this in PM 6 but I'm not quite sure what to do that isn't a lot of work. PM already has an issue where if you have, say, a NEF and a CR2 (etc) in the same folder with the same name, then an XMP sidecar file will be associated with both of them. But this is a less likely situation than having a DNG alongside a NEF or CR2 (etc) with the same name. For example I may choose to convert my NEF into a DNG with DNG Converter, and put the converted file into the same folder with the same name.
We will think this over carefully and try to fix this situation as best we can moving forward.
Regards,
--dennis
Odd Skjaeveland:
Thank you very much for commenting on this issue, Dennis.
--- Quote from: dennis on June 13, 2018, 02:37:47 PM ---sample.DNG
sample.ARW *-| These belong together
sample.XMP *-|
--- End quote ---
I guess even more entertaining things may pop up if I also put sample.JPG and sample.TIFF to the same folder with filename confusion enabled :)
It may well be the usual question of the lesser evil, and I trust you will decide on the sensible solution. PM could perhaps warn the user about conflicts and provide a list of options to rename/move, delete, overwrite etc.
Like I said, I have few problems if any, not even with DNG files from my Leica. I will happily continue with PM and Capture One in my workflow.
aram:
--- Quote from: dennis on June 13, 2018, 02:37:47 PM ---ACR uses the XMP metadata for the image loaded into PS (as we would hope), but then it also modified the DNG file to include this updated XMP, and then it deleted the XMP sidecar file! [...] If the DNG has a more recent modification date, then the XMP sidecar is ignored as far as what metadata is loaded into PS. But PS/ACR still deletes the XMP sidecar!
--- End quote ---
Hey Dennis,
This behavior can be prevented if you lock the DNG files (a.i. make them read-only). Some software like Iridient X-Transformer can be configured to produce locked DNGs by default, and then Adobe Camera Raw will do "the right thing". When you change settings, the XMP file is changed, not the DNG, the XMP is not deleted, etc.
Adobe Bridge has native support for locked files in the GUI. You can lock and unlock DNGs by right clicking on the file.
It would be great if PM would support read-only DNG workflow. My backup/version control system doesn't bode very well with large binary files that change constantly. It works very well when the RAW files never (or seldom) change, and all the edits are in a separate, smaller file.
Also, some of us we can't avoid this problem by avoiding DNGs in the first place. I use DNGs because Iridient X-Transformer can only generate DNGs, and I find ACR performs unacceptably with fuji RAF files.
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