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Archive 2012 · ? effect of making changes to DNG files in Lr ?
  
 
Alan321
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p.1 #1 · p.1 #1 · ? effect of making changes to DNG files in Lr ?


Can any of you tell me what happens when Lightroom makes changes to DNG files ? Even trivial changes such as to ratings or metadata can and probably normally would be written to DNG files but I want to know if Lr makes those changes in-situ or whether it reads the whole DNG file, makes the change and then writes the whole file out again as a new file. If it is the latter then using DNG instead of raw + XMP would incur a significant speed penalty on any system that has slow-ish data storage because with raw + XMP only the small XMP file changes and the raw file is left untouched.

Thanks in advance
- Alan



Aug 05, 2012 at 10:23 AM
Guari
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p.1 #2 · p.1 #2 · ? effect of making changes to DNG files in Lr ?


Lr is self contained. All changes made unto files are written into the catalogue file. No DNG is ever modified.

If you want to use the file outside LR with the pp changes in place, you can export to use in photoshop, or maybe as a jpg for printing, maybe a tiff. If you want you can also export your dng with a xmp sidecar file.

LR gives you many options and does not change your original file.



Aug 05, 2012 at 10:33 AM
Alan321
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p.1 #3 · p.1 #3 · ? effect of making changes to DNG files in Lr ?


Guari wrote:
Lr is self contained. All changes made unto files are written into the catalogue file. No DNG is ever modified.


You could set up Lr to work this way but it certainly can change DNG files. That is one of supposed advantages of using DNG - i.e. the metadata, etc., is all contained in the DNG file and so separate XMP files are not required. Then that single DNG file can be used in any Lr installation (including one newly installed after a drive crash) and that Lr will see all of the tweaks made by the original Lr.

The original sensor/image data may not be changed by Lr (I'm pretty sure that it is not) but other data can be and usually is.

- Alan



Aug 05, 2012 at 10:53 AM
Guari
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p.1 #4 · p.1 #4 · ? effect of making changes to DNG files in Lr ?


Alan321 wrote:
that single DNG file can be used in any Lr installation (including one newly installed after a drive crash) and that Lr will see all of the tweaks made by the original Lr.

- Alan


Hi Alan,

I've never been able to get LR to work as you say. If I go to the finder and manually look up a dng I know I have modified in LR and I reimport the file or I open the file in photoshop, I do not see the changes at all. Maybe I have some feature or tick box clicked in my LR since version 1 that prevents me from working as you say. It has always been self contained for me. That is one of the reasons why I left Aperture for good and embraced LR.

If I wanted to reimport a DNG with changes I have two ways to do it.

- Export a set of dng I have made changes as a catalogue via "export as catalogue" and reimport. It works for me because it references all the changed information made upon those dng's.

- Export with a sidecar and reimport.

That's the way it works for me...

take care, Gus



Aug 05, 2012 at 11:12 AM
 

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Alan321
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p.1 #5 · p.1 #5 · ? effect of making changes to DNG files in Lr ?


Well Gus, I can't argue about it with any authority because I have never actually used DNG. I've been happy to use raw files with no xmp files but I've just been reconsidering the pros and cons of changing over to DNG.

It would seem that one way or another it is possible to make the DNG experience match the raw with no xmp experience. Even that is useful info.

- Alan



Aug 05, 2012 at 11:51 AM
Guari
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p.1 #6 · p.1 #6 · ? effect of making changes to DNG files in Lr ?


Hi Alan,

Wish I could be of more help, I am not a pro nor anything but I've been playing with LR since it came out. Maybe there is a way to write the changes into the dng. I haven't found it.

For me (I can't stress the me part while in forums lol) I decided to finally dump the camera RAWs and just keep and work with the DNG's. I was having such a redundancy by archiving the NEF's while working on dng's. I know some people would say I am throwing proprietary info (the Nikon "sauce" in my case) into the garbage by converting to DNG's. I don't care to be honest. The DNG serves my purposes and gives me piece of mind. It's a raw file in the end, and I shoot raw in order to work it.

Sorry for the semi rant...



Aug 05, 2012 at 12:22 PM
Alan321
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p.1 #7 · p.1 #7 · ? effect of making changes to DNG files in Lr ?


It seems that you can write the metadata to a DNG by clicking on the down-arrow icon in the thumbnail in the grid view (it means that metadata has changed but has not been written to the file) or via the metadata menu items "save metadata to file" or "update DNG preview and metadata", but for DNG files it does have to be done manually.

Until the metadata is written to file the file is out of date in terms of what has been done in Lr and cannot be used to recover those changes should you lose the catalog in a crash. However, if you do write the changes then much more than just the xmp data has to be backed up by any backup program; it will fill your backup drive much sooner than later if you are saving multiple versions of files with the likes of the Apple Time Machine program.

A DNG file may be 20% smaller than a raw file but it is very much larger than a sidecar xmp file, so saving changed DNG files takes a lot more space than saving changed xmp files. It would not matter so much if you are making only a single backup without keeping previous versions, and so in part that depends on your backup strategy, the backup software and perhaps the operating system features that are in play.

- Alan



Aug 05, 2012 at 01:05 PM





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