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Author Topic: Michael's DNG comment  (Read 80728 times)

aduke

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Re: Michael's DNG comment
« Reply #120 on: August 14, 2012, 07:20:39 pm »

John, I think you are saying that, if you have not set "Automatically write changes to XMP", then your changes are not written to the DNG, so there is no need to backup the DNG file, just the Catalog.

I looked into a new DNG I just now created, made some changes in the Develop module and see not settings data at all. This seems to indicate that the creation of a DNG from an already processed CR2 does not automatically write the current settings into the DNG.  Subsequent changes to the DNG did not write the DNG either.

This is the behavior I would expect and may be different from previous versions of LR.

Alan
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James R

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Re: Michael's DNG comment
« Reply #121 on: August 15, 2012, 02:45:58 am »

Do I have this right? 

A dng contains all raw info and adjustments made by the converter, such as Capture 1 or LR?

Capture 1 cannot read the adjustments in a dng created by LR, but will read the raw data?

Therefore, communication between these converters would require a file format such as TIFF?


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john beardsworth

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Re: Michael's DNG comment
« Reply #122 on: August 15, 2012, 02:57:10 am »

John, I think you are saying that, if you have not set "Automatically write changes to XMP", then your changes are not written to the DNG, so there is no need to backup the DNG file, just the Catalog.

No, I am not saying that. Even if changes are automatically written, continually backing up the modified DNGs is redundant and only of second-class backup value.
« Last Edit: August 15, 2012, 03:41:35 am by johnbeardy »
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john beardsworth

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Re: Michael's DNG comment
« Reply #123 on: August 15, 2012, 03:03:40 am »

Do I have this right? 
No.

Quote
A dng contains all raw info and adjustments made by the converter, such as Capture 1 or LR?
A DNG contains all raw info..... metadata and updated previews.

Quote
Capture 1 cannot read the adjustments in a dng created by LR, but will read the raw data?
Capture 1 can read the adjustment settings from Lightroom but does not do so and has no practical reason for doing so. It can read metadata though. Aperture can read metadata, can display the updated previews, and can save metadata back to the DNG.

Quote
Therefore, communication between these converters would require a file format such as TIFF?
Depends how narrowly you define communication.
« Last Edit: August 15, 2012, 03:40:58 am by johnbeardy »
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sandymc

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Re: Michael's DNG comment
« Reply #124 on: August 15, 2012, 05:17:27 am »

Capture 1 can read the adjustment settings from Lightroom but does not do so and has no practical reason for doing so.

Not really - the adjustment settings are undocumented, so while C1 (or any other converter) can read the settings, it can't interpret what they mean.

Sandy
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john beardsworth

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Re: Michael's DNG comment
« Reply #125 on: August 15, 2012, 06:36:29 am »

Yes, it can read them - they're not encrypted and are logically laid out. You don't need a big brain - it's just not worth the donkey work.
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sandymc

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Re: Michael's DNG comment
« Reply #126 on: August 15, 2012, 07:01:25 am »

Yes, it can read them - they're not encrypted and are logically laid out. You don't need a big brain - it's just not worth the donkey work.

No, really ;D

Without knowing what the settings really mean, you won't get the same result. E.g. vibrance. May sound simple, but what is it measured in? How does it interact with the saturation control? There are way too many possible interactions to be able to work it out by trial and error, even if you ignore the "content aware" processing in LR. Only Adobe know that stuff, and they're not saying.

Sandy
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john beardsworth

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Re: Michael's DNG comment
« Reply #127 on: August 15, 2012, 07:26:15 am »

It is possible to read whatever is there. Whether it is fully or even marginally understood is a different matter, and translating settings to another app will always be imperfect. But you can take certain parameters and translate them - for example, you can take LR's B&W setting and send it to another app, and even LR's 8 B&W sliders could be mapped to the 6 B&W sliders in C1 or the 3 B&W sliders in Aperture. You'd have to do an awful lot of work, and it's not worth the effort.
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digitaldog

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Re: Michael's DNG comment
« Reply #128 on: August 15, 2012, 10:09:53 am »

It is possible to read whatever is there. Whether it is fully or even marginally understood is a different matter, and translating settings to another app will always be imperfect.

Agreed. If you had two products using the term Vibrance but using different math to product the results, seeing +34 Vibrance, which is spelled out in English isn’t going to translate. A bit like RGB numbers with no associated ICC profile. What color is R35/G79/B100? You’ve got only part of the recipe. So even if Capture 1 had Vibrance, +34 there and +34 in LR or ACR would produce a different result. In a raw converter that didn’t use the term Vibrance, it is an unknown term and process.
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digitaldog

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Re: Michael's DNG comment
« Reply #129 on: August 15, 2012, 10:11:35 am »

You don't need to keep backing up your DNGs - it's incomplete and redundant.

Why is it incomplete? Redundant I can understand (and frankly have no issue with).
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James R

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Re: Michael's DNG comment
« Reply #130 on: August 15, 2012, 11:04:20 am »

Thanks to all.  This has been a very interesting thread.  I will still save my important images as tiffs. 
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john beardsworth

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Re: Michael's DNG comment
« Reply #131 on: August 15, 2012, 11:07:22 am »

Why is it incomplete? Redundant I can understand (and frankly have no issue with).
Just think of all the stuff that never gets into xmp - flags, history, VCs, collections (all types), custom fields.
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digitaldog

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Re: Michael's DNG comment
« Reply #132 on: August 15, 2012, 11:58:36 am »

Just think of all the stuff that never gets into xmp - flags, history, VCs, collections (all types), custom fields.

OK, I see where you’re coming from. That be as true for proprietary raws as DNGs. The point that one needs to backup the catalog for those items is taken. We could suggest to Adobe that those items could (and should?) be embedded in a DNG making backing them up more complete. What is embedded and backed up in the DNG is adequate and some of the items you point out are not accessible in ACR so maybe keeping them in the LR catalog makes more sense.

So the workflow question I have for you is this. At some point I have to backup the DNG. I’ll backup the catalog on a regular basis. But I’m adding newer DNG’s all the time. Plus occasionally updating older DNGs. Currently any change made, even a tiny metadata update will force the backup app to treat this file as needing to be backed up. How do we control this such that DNG’s that have never been backed up get backed up, DNG’s that were once backed up but result in a small change don’t get backed up?

At this point, my backup routines are automated so I’d rather err on the side of backing up a DNG that has a tiny change than not backup a DNG that isn’t backed up. Where it gets slow and somewhat dicey is backing up to the cloud (CrashPlan) which is far slower than backing up to local drives.
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john beardsworth

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Re: Michael's DNG comment
« Reply #133 on: August 15, 2012, 12:25:35 pm »

My approach is to separate them physically - new stuff goes on one drive where it gets backed up, and the files are then moved onto a drive not scanned by the backup software. I think that's broadly the same as Peter K does.

As for the stuff that isn't backed up, I've been making the case for backing up custom fields since the day they became possible in LR. After all, that does happen in Bridge (where custom fields are equally obscure!). I'm more surprised that VCs aren't included, though again I've lost hope as Adobe don't seem to want to merge the VC and Snapshot concepts as I keep suggesting. Flags could be viewed in Bridge, so I'd expect them to appear in the XMP - one day....
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digitaldog

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Re: Michael's DNG comment
« Reply #134 on: August 15, 2012, 12:35:30 pm »

My approach is to separate them physically - new stuff goes on one drive where it gets backed up, and the files are then moved onto a drive not scanned by the backup software. I think that's broadly the same as Peter K does.

Now I have to decide if it is worth the time to use two drive systems to avoid the auto backup. One takes work on my part, the other doesn’t. I do know that Peter has concerns backing up the same file over and over again.
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Alan Goldhammer

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Re: Michael's DNG comment
« Reply #135 on: August 15, 2012, 06:13:31 pm »

Andrew and John raise some interesting points but the consideration should be what is necessary for the image and what is necessary for the management software.  Each software development may implement their database management in a slightly different manner and my thinking is that should not be part of the DNG standard, if we ever get to that point.  The DNG should be image and not collection dependent, thus things such as flags, ratings, etc would not.  I think this is what I'm reading in your posts but correct me if I'm wrong.

I'm still at the point of keeping everything in NEF format and using XMP files.  This makes backups to the cloud (Mozy) simple after the initial image is backed up.  I had 800 images when getting back from Italy and it all was backed up pretty quickly.  It's not clear to me with DNGs what the backup times will be if all the changes are incorporated into them rather than XMP.
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john beardsworth

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Re: Michael's DNG comment
« Reply #136 on: August 15, 2012, 06:34:46 pm »

The beauty of DNG, Alan, is that we don't need to worry too much about issues such as storing information such as Lightroom collections. That's of concern only to Lightroom users, but the wider point is that DNG can store any such information inside the file (would you want to write it into a NEF or CR2?), and metadata that's embedded is usually much easier to move to other apps.

Your point about the time storing XMP files versus backing up DNGs is important and is what I'm driving at. When you get back from Italy, backing up a NEF and its XMP will be no different to backing up a DNG at its creation. But after that, when you make further changes to the picture, there's no point repeatedly backing up the DNG.
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Alan Goldhammer

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Re: Michael's DNG comment
« Reply #137 on: August 16, 2012, 08:50:53 am »

The beauty of DNG, Alan, is that we don't need to worry too much about issues such as storing information such as Lightroom collections. That's of concern only to Lightroom users, but the wider point is that DNG can store any such information inside the file (would you want to write it into a NEF or CR2?), and metadata that's embedded is usually much easier to move to other apps.

Your point about the time storing XMP files versus backing up DNGs is important and is what I'm driving at. When you get back from Italy, backing up a NEF and its XMP will be no different to backing up a DNG at its creation. But after that, when you make further changes to the picture, there's no point repeatedly backing up the DNG.
The point that I'm not clear about is whether XMP is used along with DNG here.  If you have metadata within the DNG doesn't that mean that it is part of that particular file?  If so, the backup system sees a time stamp that the DNG has changed and then requires a back up to be done.  How can just the metadata be backed up and not the whole DNG?  that't the puzzle I am working through here though maybe I need to look at the DNG standard to see how this really works.
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digitaldog

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Re: Michael's DNG comment
« Reply #138 on: August 16, 2012, 09:32:16 am »

The point that I'm not clear about is whether XMP is used along with DNG here.  If you have metadata within the DNG doesn't that mean that it is part of that particular file?  If so, the backup system sees a time stamp that the DNG has changed and then requires a back up to be done.

Some of the XMP is ‘inside’ the DNG if that is a kosher term to use. Some is inside the catalog. What I think I’m hearing is this: backup the DNG initially and then stop because some of the information is now applied inside the LR catalog which of course we’ll backup every time something new changes. But some info IS updated in the DNG as you continue to edit and if you force the Update DNG Preview and Metadata command, there’s a lot that gets updated into the DNG I’d personally want backed up again (example is a DNG profile).
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john beardsworth

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Re: Michael's DNG comment
« Reply #139 on: August 16, 2012, 09:44:39 am »

The point that I'm not clear about is whether XMP is used along with DNG here.  If you have metadata within the DNG doesn't that mean that it is part of that particular file?  If so, the backup system sees a time stamp that the DNG has changed and then requires a back up to be done.  How can just the metadata be backed up and not the whole DNG?  that't the puzzle I am working through here though maybe I need to look at the DNG standard to see how this really works.
You understand it correctly, Alan. LR writes XMP metadata inside the DNG and in my case my main LR catalogue has the automatic setting switched on. Sure, that means the DNG has changed - but that's not enough of a reason to back up the DNG again. People simply assume it must be so, but that's because the assumption is so rarely challenged.

But let's say I did back up the changed DNG, I would be missing a varying proportion of the LR work I've done on the picture, so the backed-up DNG would only be a second rate backup. It would also be redundant - I can recover 100% of my work from the backup of the DNG when it was created (my "new work" drive is covered by the backup) and by daily catalogue backups.

[Edit] If people want to keep backing up their DNGs they should go right ahead - it does no harm - but don't let the anti-DNG brigade get away with the idea that DNG means bigger backups.

John
« Last Edit: August 16, 2012, 09:48:56 am by johnbeardy »
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