Author Topic: IPTC and DNG files  (Read 6546 times)

Offline roysmyth

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IPTC and DNG files
« on: July 03, 2006, 11:50:09 AM »
When I modify the IPTC data in a DNG file, a sidecar file is created.

Is there a way to have Photo Mechanic edit the IPTC data stored within the DNG file rather than adding a sidecar?

If not, please make this a feature request.

Offline Kirk Baker

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Re: IPTC and DNG files
« Reply #1 on: July 03, 2006, 12:45:59 PM »
When I modify the IPTC data in a DNG file, a sidecar file is created.

Is there a way to have Photo Mechanic edit the IPTC data stored within the DNG file rather than adding a sidecar?

If not, please make this a feature request.

Yes.  You need to adjust the IPTC/XMP settings.  Open up the Preferences dialog.  Click on the IPTC/XMP tab.  In the section titled "When writing IPTC/XMP:" look for the set of controls below the text titled "For TIFF-based RAW photos:".  There are two checkboxes and a popup menu.  The two checkboxes control what is written to TIFF-based RAW files (DNG is a TIFF-based RAW file), and you'll need to set one or both of them to checked (depends on if you want XMP data as well as IPTC data inserted into your DNG files.)  But it is the popup menu that you'll have to change to the last option: "If XMP sidecar files exist, only update IPTC4XMP if present".

This will cause PM to never create an XMP sidecar file, and it will only update the IPTC4XMP data if it already existed in the already existing XMP file.

HTH,

-Kirk

Offline Hydester

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Re: IPTC and DNG files
« Reply #2 on: July 03, 2006, 01:07:54 PM »
This is really helpful & I have just changed my preferences.  I am sure there is a good reason why not, but should this not be the default setting (ie "If XMP sidecar files exist, only update IPTC4XMP if present".) ?

Offline Kirk Baker

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Re: IPTC and DNG files
« Reply #3 on: July 03, 2006, 01:12:15 PM »
This is really helpful & I have just changed my preferences.  I am sure there is a good reason why not, but should this not be the default setting (ie "If XMP sidecar files exist, only update IPTC4XMP if present".) ?

Our rationale is that if an XMP sidecar file exists and you are editing IPTC/XMP then you have an XMP sidecar workflow and thus the IPTC/XMP data should go there too.

-Kirk

Offline roysmyth

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Re: IPTC and DNG files
« Reply #4 on: July 03, 2006, 04:58:19 PM »
A number of questions come to mind.

1. When I work with raw files from the camera, I would like all annotation to go into an XMP sidecar file and I would like the the raw file unchanged. What preferences should be set to do this? I would like the XMP sidecar data to take precedence over any metadata in the raw file.

2. When I work with a DNG file, I would like all metadata to go into the DNG file and have no sidecar file created. I assume the preferences to do this contradict the ones for the above question, and that I can't have DNG files treated differently than raw files from the camera.

3. Why ever create a sidecar for DNG? A strength of DNG is that it is a documented format and sidecars aren't needed. AFAIK, Adobe software only ever creates a sidecar for a DNG file when it encounters a read-only DNG file. DNG files are not like other raw files and should not be treated as such. (Feature request / bug report.)

4. What does PM do with existing embedded DNG metadata when it creates a sidecar? Does it copy all the existing metadata into the sidecar and then add its changes or additions?

5. (Perhaps a question for the Adobe DNG forum.) What does the DNG converter do when it processes a DNG file with an associated sidecar file? It creates a new DNG with no sidecar, but it has two sets of metadata to deal with. I assume it honours the sidecar as Adobe would only put data there when the original DNG can't be written.

Offline Kirk Baker

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Re: IPTC and DNG files
« Reply #5 on: July 03, 2006, 06:43:48 PM »
A number of questions come to mind.

1. When I work with raw files from the camera, I would like all annotation to go into an XMP sidecar file and I would like the the raw file unchanged. What preferences should be set to do this? I would like the XMP sidecar data to take precedence over any metadata in the raw file.

Turn off the two checkboxes that say "Add embedded..."

Quote from: roysmyth
2. When I work with a DNG file, I would like all metadata to go into the DNG file and have no sidecar file created. I assume the preferences to do this contradict the ones for the above question, and that I can't have DNG files treated differently than raw files from the camera.

That's correct.

Quote from: roysmyth
3. Why ever create a sidecar for DNG? A strength of DNG is that it is a documented format and sidecars aren't needed. AFAIK, Adobe software only ever creates a sidecar for a DNG file when it encounters a read-only DNG file. DNG files are not like other raw files and should not be treated as such. (Feature request / bug report.)

Why because maybe a user doesn't want us modifying their DNG files which are still RAW files.  Don't let the open specification fool you.  It is still a RAW file: it is a documented RAW file.

Quote from: roysmyth
4. What does PM do with existing embedded DNG metadata when it creates a sidecar? Does it copy all the existing metadata into the sidecar and then add its changes or additions?

Yes it does exactly what you said.

Quote from: roysmyth
5. (Perhaps a question for the Adobe DNG forum.) What does the DNG converter do when it processes a DNG file with an associated sidecar file? It creates a new DNG with no sidecar, but it has two sets of metadata to deal with. I assume it honours the sidecar as Adobe would only put data there when the original DNG can't be written.

I can't answer that one.  But experimentation would likely demonstrate what the DNG convertor does do in practice.

-Kirk

Offline roysmyth

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Re: IPTC and DNG files
« Reply #6 on: July 03, 2006, 10:14:58 PM »
Why because maybe a user doesn't want us modifying their DNG files which are still RAW files.  Don't let the open specification fool you.  It is still a RAW file: it is a documented RAW file.


-Kirk


I think that those of us who use DNG files would like Photo Mechanic to give the option of modifying the DNG file. It makes sense in a digital workflow to treat DNG not just as another raw file, but as a special, trusted case. I don't want to modify preferences every time I switch from working with Nikon's proprietary format to Adobe's open format.

It is a pain to run DNG files through the DNG converter again to get rid of the sidecar file. It is a worry if you don't as you don't know how other applications will handle a DNG sidecar.

Offline Kirk Baker

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Re: IPTC and DNG files
« Reply #7 on: July 03, 2006, 10:53:25 PM »
Why because maybe a user doesn't want us modifying their DNG files which are still RAW files.  Don't let the open specification fool you.  It is still a RAW file: it is a documented RAW file.

I think that those of us who use DNG files would like Photo Mechanic to give the option of modifying the DNG file. It makes sense in a digital workflow to treat DNG not just as another raw file, but as a special, trusted case. I don't want to modify preferences every time I switch from working with Nikon's proprietary format to Adobe's open format.

It is a pain to run DNG files through the DNG converter again to get rid of the sidecar file. It is a worry if you don't as you don't know how other applications will handle a DNG sidecar.

We'll think about it, but I think everyone will agree that the IPTC/XMP tab doesn't need to get any more complicated.  It has enough options to control precedence on reading and actions on writing, though it doesn't have specific settings for particular RAW types.  If we go down the road of making an exception for DNG RAW files, then we'll likely need individual settings for all RAW files that we support.

I'll let you know what we decide.

-Kirk

Offline Kirk Baker

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Re: IPTC and DNG files
« Reply #8 on: August 04, 2006, 02:31:23 PM »
Roy,

Why because maybe a user doesn't want us modifying their DNG files which are still RAW files.  Don't let the open specification fool you.  It is still a RAW file: it is a documented RAW file.

I think that those of us who use DNG files would like Photo Mechanic to give the option of modifying the DNG file. It makes sense in a digital workflow to treat DNG not just as another raw file, but as a special, trusted case. I don't want to modify preferences every time I switch from working with Nikon's proprietary format to Adobe's open format.

It is a pain to run DNG files through the DNG converter again to get rid of the sidecar file. It is a worry if you don't as you don't know how other applications will handle a DNG sidecar.

We now treat DNG files the same way we treat JPEG, TIFF, and PSD.  We no longer create XMP sidecar files for DNG.  IPTC and/or XMP data is always embedded into the DNG itself.  If an XMP sidecar file for a DNG is found, we do continue to update it.

This change appeared in version 4.4.3.2.

-Kirk