Updating DNG files in Lightroom

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Jim Wilde

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Feb 1, 2010
West Sussex, UK
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Just starting to experiment with DNG (from Canon CR2). LR settings for DNG creation on import are for a full-size jpeg preview, but not to imbed the original raw (yet, jury is still out on that). So I import a raw file which is converted to dng, do a few adjustments, then to update the metadata and jpeg preview with the adjustments I choose ‘Update DNG preview and Metadata’....LR then does its thing and hey presto I can then open the updated DNG in Bridge/PS3 and see the adjusted image. All as expected, apart from the fact that I end up with a new (21mb) file in my Recycle Bin (imagename.bak)...so I’m guessing that when LR “does it’s thing”, the process is something like: rename current file to imagename.bak, write new file with new metadata and preview to imagename.dng, then (on successful completion of the new file creation) the .bak file is deleted and so ends up in the Recycle Bin.

Is that the way it is supposed to work? Is there a way of preventing the deleted file ending up in the Recycle Bin? Not a major issue, though useful to be aware especially if working on a couple of hundred images that your hard drive space is being eaten up by these unanticipated created/deleted files.

I'm not sure where your process differs from mine, but I get no "imagename.bak" in the recycle bin. The RAW file that my canera produces is already DNG, so there is no conversion to DNG from a proprietary RAW format. I don't use Bridge, just LR. LR writes all the metadata changes back to my original master. It does not create a "*.bak" along the way. So I would suggest looking into either the process that creates a DNG from a CR2 or something that happens in Bridge (unlikely). You can look at your DNG using EXIFtool to see the XMP section if you want to eliminate Bridge from the sequence. for further sluething.
Thanks for the quick reply. The 'problem' is definitely not part of the import conversion of CR2 to DNG (imported several, but only the one that I worked on had a .bak file in the Recycle Bin). Nor is is anything to do with Bridge as I can recreate it by just staying within Lightrrom and not invoking Bridge/PS at all.

Part of the problem is my lack of understanding about how LR works in relation to dng adjustments...whislt I know that the catalog is updated in real-time, I had assumed that the dng metadata was NOT updated in real-time. Hence my use of the 'Update DNG preview and Metadata' command, because I thought that's what I needed to do to get the metadata updates into the file. For sure, it's this process which creates the .bak file and chucks it away again (empty the Bin, select a dng in LR, click the Update command and watch the Bin icon change to full as the dng update process ends). Look in the Bin afterwards and there's that imagename.bak file...

So now that I realise the dng metadata IS updated in real-time, I guess I only need to use that Update process if I need to update the embedded jpeg preview... and remember to empty the Bin afterwards! :)
TNG you are correct. You don't need to update the preview but if you do, the dng will be trashed after the new version is created and ends up in your bin. This is the same on macs also. It is a bit of a pain in my opinion and I'm hoping that behaviour will change in the future.
Nik, thanks for the confirmation....thought I was being even more stupid than usual! :)
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