M8 DNGs with data validation hash?

[tho3hite]

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The newest v1.3 DNG spec from Adobe (July 2009) includes embedding a data hash into the DNG file that can be used to confirm a files integrity later on.

 

Does anyone know if this is has been implemented on the M8 and when (firmware version?) Leica started using this?

 

Failing an answer to #1 does anyone know an email address were technical quesitons of this sort can be sent to Leica?

 

The hash is the best method currently available to confirm at a later date that your valuable images are still intact. It would be nice to get confirmation from Leica that they are supporting this valuable tool.

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[tho3hite]

After doing some experiments on test files from my M8 with firmware 2.004 I found that Leica is NOT using a data integrity hash in the M8 DNG files.

 

Now does anyone know where we go to tell Leica that this is an important data security tool and that we want our cameras to use it?

 

 

 

«« P.S. Can someone send me a DNG file from a M9 to test »»

[stunsworth]

So what would you do if you found a file where the hash total was wrong? Are you any better off than not knowing - isn't the real test when you attempt to open the file?

[wstotler]

tho3hite:

Thanks for the investigation. Would be interested to know about the M9 DNGs.

 

Steve:

The hashtag could be useful later when running a utility against a large batch of images to identify issues that have crept into the DNGs in your filestructure.

 

Let's say a file, or set of files, became corrupted on your HD. You could run a batch job against those to find the corrupted images and, if you have a backup of those files, restore the damaged files.

 

This assumes the hashtags are correct at "write time," in the camera. (If they're wrong, there's a bug that requires a fix.) This also assumes that the hashtag value doesn't become corrupted in the file itself on your hard drive. This also assumes smart backups of your files (with a correct hashtag) are being made by you, so you can later restore files.

 

More: "The latest versions of Adobe Lightroom and Adobe Camera Raw will also perform a validation of DNG files, but neither of these programs makes it easy to validate a large number of files at once. Lightroom will only validate one image at a time in the Develop module. Camera Raw will validate all images that are loaded into Camera Raw, but this gets cumbersome to accomplish with more than one folder at a time. . . . We should see a number of applications taking advantage of this code in the near future." Source: http://www.dpbestflow.org/data-validation/dng-validation

 

Right now this has theoretical utility. I know that with a growing image library (70K+ images), having something to zip through the files and have a look for potential issues wouldn't be a bad idea. It's certainly easier to run a batch utility that peers into the files and does a checksum on each file, rather than trying to compare filesizes between originals and different versions of the DNGs stored on your filesystem.

[pop]

There have been several reports of garbled image files with M8s and M9s. Even if all of those were due to user error handling the card or unsupported cards, I'd think it would be worth while if it was possible to run a quick and automatic check on all files of a card.

 

Assume you were on an outing not likely to be repeatable and took dozens of shots (or thousands). You'd then placed the storage card into you netbook and checked if any files were suspect.

[cbretteville]

Haven't looked at the latest DNG spec to see what kind of fingerprint Adobe has defined. I do know Canons can be equiped with a gizmo that stores an MD5 of the image data in the files for forensics use. It could be this is what the tag is intended for.

Carl

[sandymc]

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To pick up a few of these questions:

 

1. Digests for both the raw image data and the embedded raw file (not applicable to a native DNG file) are defined from DNG version 1.2 onwards.

 

2. These are MD5 hashes

 

3. Neither the M8 or the M9 use these; both cameras implement DNG 1.1, not later.

 

If you want, you can add hashes by running your images through either Lightroom or DNG convertor. Note however that as far as I am aware, only Adobe products (so Lightroom or Camera Raw) will ever look at these tags.

 

Sandy

[cbretteville]

That figures Sandy.

One warning, if you do rewrite M8 files, the maker notes information is lost as Leica haven't included the MakerNotesSafety tag in the set of tags that comprise the EXIF info in the M8 files. It is there in the files written by the M9.

 

The information is also lost if you open an M8 DNG file in Adobe Camera Raw as it rewrites the meta data information when you click [open], very nasty. Lightroom does not change the file at all so in that sense it is a lot safer. To avoid this with ACR you need to hold down the [Alt] key to get [Open as copy] and click that.

 

Carl

[tho3hite]

That figures Sandy.

One warning, if you do rewrite M8 files, the maker notes information is lost as Leica haven't included the MakerNotesSafety tag in the set of tags that comprise the EXIF info in the M8 files. It is there in the files written by the M9.

 

Carl

 

What information gets stored in the MakerNotes tag?

 

Thomas

[sandymc]

What information gets stored in the MakerNotes tag?

 

Thomas

 

All explained in the link in Carl's signature: the m8 metadata project

 

Sandy

[mhoersch]

Since firmware 2.004 is from September 2008 it can't include anything that came later. Interesting question, though, for the next firmware version - if there will be any. But we won't go into that again, won't we?