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Author Topic: Best way to confert RAW files to DNG: Use LR or Adobe Coverter  (Read 5285 times)
JoeThePhotographer
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« on: February 08, 2011, 10:55:29 AM »

What is the best procedure for converting existing library (RAW and possibly JPG and TIFF) to DNG?  Should I create xmps and then use the standalone converter, or should I convert from within LR?

I would like the settings and metadata which exist in the LR catalogue to be saved into the DNG.  Is this possible for all settings, or are some things "left behind"?  How about virtual copies of one pic that exist in the LR catalogue--will all copies be included in the DNG?  Will LR and ACR always know what camera the photos originated from for the purpose of applying proper camera-specific settings?

Joe
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JoeThePhotographer
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« Reply #1 on: February 09, 2011, 06:07:41 AM »

I did some experiments and found a few interesting things:

(1) Converting JPG to DNG increases their size greatly.  From 2 Meg to 10 Meg, for example.  I knew there would be an increase but did not know how much.  This does not seem like a good option, especially since metadata can be written directly to JPG (though I was hoping to take advantage of hash validation).  Luckily, I don't shoot jpg any more.

On to the problem with Virtual Copies:

(2) Exporting Virtual Copies from LR3 creates one DNG file for each Virtual Copy.

(3) There is no other way of letting Bridge or ACR recognize virtual copies.  If you have virtual copies in LR catalogue, you can write virtual copy to disk ("Update DNG Previews and Metada") but only one of the Virtual Copies will be written to disk.  Neither xmp nor DNG format accomodates more than one virtual copy.  The only way to share virtual copies with Bridge/ACR is to create additional DNGs by "Exporting to DNG".

Other observations/issues:

(4) DNG metadata does not get automatically written to choose either "Save Metadata to File" or "Update DNG Previews and Metada".  Not sure exactly what the difference is.  But the big question is: does the metadata continue to live in the LR catalogue or not?  If not that is a problem because I regularly bakup the catalogue but I never backup photos after initial importation and archiving.

(5) Converting a TIFF to DNG, at least in one case, reduced its size considerably.  This might be a good option for scanned photos.
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johnbeardy
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« Reply #2 on: February 09, 2011, 09:32:34 AM »

JPGs are 8 bit while DNGs hold 16 bit data. I know Peter wants it to be possible to save JPEGs as original 8 bit data.

Bridge won't understand virtual copies, because VC info isn't written to the XMP data inside the DNG. But it will understand Snapshots since that information is written, and there's a plug-in called Snapshotter that converts VCs to Snapshots.

Save metadata and the automatic option do work. How are you testing this?

John
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JoeThePhotographer
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« Reply #3 on: February 09, 2011, 09:48:17 AM »

JPGs are 8 bit while DNGs hold 16 bit data. I know Peter wants it to be possible to save JPEGs as original 8 bit data.

That would be a good thing!  I predict it would help DNG become a dominating force, which it isn't right now.

Bridge won't understand virtual copies, because VC info isn't written to the XMP data inside the DNG. But it will understand Snapshots since that information is written, and there's a plug-in called Snapshotter that converts VCs to Snapshots.

Does Bridge understand multiple snapshots?  How do you access them in Bridge?

Save metadata and the automatic option do work. How are you testing this?

I did not have the automatic option enabled.  I will try again.  When you update a DNG file, does the catalogue retain the information?  This is very important, in case a colleague (who doesn't have access to my catalogue) messes with a DNG file.

Do you have any insight on whether to convert TIFFs to DNG?  I am referring only to TIFFs that represent the initial scan from a scanner, not works in progress or final output.

Joe
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Roelof
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« Reply #4 on: March 31, 2013, 04:16:11 AM »

Even with no changes or 'special' issues involved there are differences between DNG's generated with DNG converter an LR:

(original image at: https://dl.dropbox.com/u/25580003/DNG_DNCconverter_VS_LR.JPG)
With the same settings (compatibility with ACR 7.1 and higher) the DNG from DNG converter is 30,18 Mb and the one generated wiht LR is 27,91 Mb.
I can use/see the DNG from DNG converter in my file system browser, Expression Media and bridge but the DNG from LR is only visible in Bridge...
Is there something i'm doing wrong? (i'm using LR since a few days only)
Roelof
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