Recovering/repairing damaged DNGs

[LocalHero1953]

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I have found around 20 edited DNG files which are unreadable and uncopyable. They are not in the same folder, nor related in any other way that I can see. They are on a newish 10Tb disk (so they were copyable at the time that was set up).

• They have been in my Lightroom catalog for quite a long time - years. They can be displayed there, but not edited, nor exported as jpg or tif. I assume I am seeing an embedded preview image. If I remove them from the catalog, I can import them again, but with the same limitations; this time the previous edits have been lost.
• Photoshop will not open them.
• My Lacie backup software will not copy them to the backup disk, but gives an error message.
• Windows Explorer will not copy them to another location.

I don't think that any of the files are particularly valuable images. I should have old copies on Backblaze. If the worst comes to the worst, I shall display them on screen at the highest res I can, and save them as screen shots. 

Is there any software that can repair DNG files? Since Windows Explorer cannot touch them, it may be the damage is nothing to do with the image format.

All ideas welcome!

 

Edited January 13, 2023 by LocalHero1953

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[wda]

Hi Paul,
If you can access the raw files’ metadata, you can see where the files are located and their sizes. Does the data look correct for raw files of their time? If not you are probably looking at catalogue thumbnails. The original files are probably lurking on an old backup drive somewhere.

[LocalHero1953]

7 minutes ago, wda said:

Hi Paul,
If you can access the raw files’ metadata, you can see where the files are located and their sizes. Does the data look correct for raw files of their time? If not you are probably looking at catalogue thumbnails. The original files are probably lurking on an old backup drive somewhere.

Thanks, David. In Windows Explorer the files are visible and show as the correct size; as 'Extra large icons' they have the correct image. Good idea about checking metadata.

Edited January 13, 2023 by LocalHero1953

[Anbaric]

3 hours ago, LocalHero1953 said:

Thanks, David. In Windows Explorer the files are visible and show as the correct size; as 'Extra large icons' they have the correct image. Good idea about checking metadata.

If you right-click a file from Windows Explorer and select 'Properties', what do you see for the filename (including extension), 'Type of file', 'Size' and 'Size on disk' and 'Attributes' in the General tab? What permissions are ticked 'Allow' in the 'Security' tab? Is there anything else in Properties that's different between a good and a bad file? You might try posting screenshots of the Properties box (Alt-Print Screen will copy it to the clipboard).

You could also try a Malwarebytes scan to see if there's anything suspicious going on:

https://www.malwarebytes.com/

[LocalHero1953]

The file name and extension are shown as correct in 'Properties', as is the file size - the same as the other files in the same folder. The dates are correct as far as I can remember. Edit: all the users on the Security tab have full access, nothing 'Denied'; the EXIF data in the Details tab looks correct.

I said incorrectly that the files are on a newish 10Tb hard disk - they are actually on a 4TB SSD, and have been there for a few years.

I have downloaded copies from Backblaze, and they don't exhibit any of the problems of the originals: they open in Photoshop, and Lightroom is prepared to import them, though I haven't done so yet.

It has become a matter of curiosity now - to find out what's happened and how they could be recovered. I'll try Malwarebytes later.

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Edited January 13, 2023 by LocalHero1953

[jaapv]

What happens when you run them through Adobe’s DNG converter? 

[LocalHero1953]

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1 hour ago, jaapv said:

What happens when you run them through Adobe’s DNG converter? 

I downloaded it and navigated to the folder containing the problem files, but none of the files (good or bad) were visible - presumably because they were all DNGs already. I tried the 'Extract' option - same result. I tried dragging a file to the app icon as suggested, but it showed a mini 'no entry' icon. I haven't had to use this app before, so tell me if I've missed something!

Malwarebytes finds no problems with the file.

There are a number of apps that supposedly recover damaged DNG, image or other files: Stellar, Repairit etc. I have used a Stellar app before to recover deleted files. Has anyone used one of these apps for image files? Unless I hear anything I will try one of them.

[Anbaric]

What error message do you get when you attempt to copy the file to a different location using Windows Explorer?

Depending on the problem, something like Unlocker might work:

https://www.majorgeeks.com/files/details/unlocker_portable.html

or one of these tools:

https://www.raymond.cc/blog/copy-locked-file-in-use-with-hobocopy/

I've successfully used PhotoRec for file recovery, but that's really for deleted rather than damaged files:

https://www.cgsecurity.org/wiki/PhotoRec

[jaapv]

1 hour ago, LocalHero1953 said:

presumably because they were all DNGs already

That is not correct. DNG  Converter accepts DNG files for "re-DNGing". Can you rename the files to .TIFF ? That sometimes works. I think it is just the header that is corrupt.

[LocalHero1953]

4 hours ago, Anbaric said:

What error message do you get when you attempt to copy the file to a different location using Windows Explorer?

 

This:

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[LocalHero1953]

3 hours ago, jaapv said:

That is not correct. DNG  Converter accepts DNG files for "re-DNGing". Can you rename the files to .TIFF ? That sometimes works. I think it is just the header that is corrupt.

Hmm. DNG converter asked to select a folder from which to choose an image to convert, but did not show me any of the files in it - I assumed it was because they were all DNG.

However, I right clicked the file, selected 'Open With' and chose DNG Converter. This was the error message.

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[marchyman]

I know nothing about windows and just enough about file systems to be dangerous 🙂

With that said an unreadable file is sometimes unreadable because of a corrupted directory entry.  The system reads the directory and tries to access the file but the data in the directory about the file makes no sense to the system.   Because of that possibility the first thing I'd do is run some kind of filesystem repair program.  A search points to this page ==> https://support.microsoft.com/en-us/topic/use-the-system-file-checker-tool-to-repair-missing-or-corrupted-system-files-79aa86cb-ca52-166a-92a3-966e85d4094e for Windows Vista through Windows 10.

The ultimate fix is to restore the original image from backups.

[Alberti]

I have also had a couple of files exhibit this, on my iMac, with an external disk. This was after moving file storage disk (copy to new SSD's). So it appears it is not isolated to Windows environments. Same catalogue, moved files manually, then gave LR the new 'address'.

I also went into the file with amongst others the Adobe converter. Same response.

I know LR wants to move the files themselves, but that is tedious sometimes. Anyway, I shrugged my shoulders.

Edited February 17, 2023 by Alberti