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Author Topic: Why NOT to use DNG  (Read 8626 times)
DigitalOxygen.ca
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« on: January 14, 2011, 08:03:52 PM »

I am on the fence.  I have been considering DNG on and off for quite some time and after all my reading and analysis I am still undecided.

I have decided to reach out for advice in a slightly different manner and list some of the typical reasons people suggest switching to DNG and my thoughts on those points  In some cases I think those are actually reasons NOT to convert to DNG.  I really want to use DNG but there are a few hangups that leave me with less than full confidence in making the switch and I want to be convinced otherwise.

So... convince me!  Counter my points and correct my misunderstandings and misconceptions!

Here goes:


XMP sidecar files:
I fail to see how .xmp files cause any headache, at least related to backups.  When you backup RAW files you are typically backing up entire folders or even entire drives so the backup of those files is handled automatically.  Unless for some very strange reason you are backing up individual RAW files in a folder and thus must backup the associated sidecar files I don't see this as an issue.

You could actually consider sidecar files more beneficial than DNG when you consider incremental backups.  If you use RAW + .xmp your edits are saved into the .xmp file (or in the lightroom catalog but that's another topic).  This means that come backup time only the tiny .xmp files need to be backup up because the comparatively huge RAW files are already backed up and have not changed.


Space Savings:
Although the DNG lossless compression is more efficient than native RAW no question there.  Whether the potential 5% to 20% space savings is worth it with the cheap prices of storage these days is debatable.


Editing Capabilities:
Although DNG claims to store all the proprietary native RAW information we don't really know for sure because there is currently no way to extract or verify that information and use it (i.e. a DNG to RAW converter that many are asking for).  Although DNG gives you additional capabilities such as a (potentially) wider range of software and better embedded thumbnail support (i.e. can see your edits) you lose some of the capabilities you have in the camera manufacturers software such as the ability to display the auto focus points that were active at the time of exposure. 

UPDATE: Turns out there are a few pieces of software that can read and utilize the af point data inside the DNG. I have verified Breeze Browser Pro can do it and apparently Photo Me as well as the "Viewfinder" Lightroom plugin can/will do it if/when it's released.  This still does not fully sell me on DNG though because there may be other information that is "locked" inside the DNG that is unusable by anything other than the camera manufacturers own software... which is only usable when the image is in the original RAW format.


Verification
According to the bpbestworkflow site the best way currently to verify DNGs is to run them through Adobe's DNG converter software which essentially re-converts them to DNG. https://www.dpbestflow.org/data-validation/dng-validation  What benefit does this provide over just converting the original RAW files to DNG in order to verify them?  Seems that either way the source file is read and an error is reported if there is a problem.  How is DNG better here?


What about the future?
The argument here is that if Canon, Nikon, Lightroom, ACR, etc. ever disappear (company's go under, support is discontinued, etc) future computer hardware/software will not be available or process the RAW files.  I find it EXTREMELY unlikely that I will see a point in my lifetime or beyond where it is technically impossible to process a native RAW file from Canon or Nikon.  Why?  Because with advancements in things like virtualization it will almost always be possible to boot up a version of any old OS and the associated software needed to process the RAW files.  For those who are really that paranoid just keep a copy of your current OS and camera manufactures RAW processing software for the future and fire it up in a VMware or VirtualBox environment and batch convert to DNG.


Please response to the section specifically if possible.  I am hoping to make this a learning experience for everyone.
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markpirozzi
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« Reply #1 on: January 15, 2011, 05:34:03 AM »

XMP sidecar files:

You could delay conversion of the proprietary RAW files to DNGs until finished all editing prior to archiving.  During this phase, the incremental backups would be small.

What about the future?:

Some people keep the original proprietary RAW files (outside of the DNG file) to hedge their bets.  To save storage space, you could delete all but your 3, 4 and 5 star images after archiving the DNGs.

Mark
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JoeThePhotographer
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« Reply #2 on: February 08, 2011, 10:42:05 AM »

Is this board active?

On the validation point, RAW to DNG conversion cannot validate whether the file has changed.  Maybe it can report whether the file is damaged; not sure about that.  But it certainly can't tell whether it has changed because no hash was ever created.  Once it's DNG hashes are created, so you can tell if even a single bit has changed in either the DNG or if you embed the RAW, the RAW portion as well.

As far as xmp, they're a major hassle.  I just deleted serveral thousand of them.  I have no idea what program created them or what they say, so I deleted them.  All the useful info about my files is stored in the LR catalogue, I think.

My only misgivings about DNG are that (1) I'm presuming the DNG converter discards some proprietary info present in the RAW file (right?) and (2) I don't think Microsoft supports DNG yet in its 64bit operating system (how does that bode for otehr software vendors supporting it?). 

Despite my misgivings, I am about to convert all of my raw files (from Nikon, Panasonic and Olympus cameras) because (i) xmp are such a major hassle, and I want all of my Adobe programs and LR catalogues to know what changes I've made to the file, (ii) validation is very underrated, once you have 100K + files, (iii) it's nice to save a bit of space.  My 2TB drive is quickly getting filled up with photos and video.

I think I might keep a RAW version (embedded in DNG) of my top, top files.  The 1% top eshelon of  keepers.
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JoeThePhotographer
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« Reply #3 on: February 08, 2011, 10:48:46 AM »

Verification
According to the bpbestworkflow site the best way currently to verify DNGs is to run them through Adobe's DNG converter software which essentially re-converts them to DNG. https://www.dpbestflow.org/data-validation/dng-validation  What benefit does this provide over just converting the original RAW files to DNG in order to verify them?  Seems that either way the source file is read and an error is reported if there is a problem.  How is DNG better here?

Look at the other page of https://www.dpbestflow.org/node/301, which states:

Keep in mind that just because a file can be opened and converted by the DNG Converter does not mean that the image data inside the file is problem-free. It's possible that the file structure is intact, but the image data is corrupted. For full validation of the image data, you'll want to save raw files as DNGs.
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