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Author Topic: Lightroom v3 b2 and DNG files  (Read 3031 times)

Mike Arst

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Lightroom v3 b2 and DNG files
« on: May 03, 2010, 02:34:41 pm »

With a computer that's ancient by today's standards -- single proc/single core, Win XP SP2, only 1 GB of RAM -- I can't expect high performance from any graphics-related apps (can't run CS4 at all -- it freezes not long after launch; have to use CS2 instead; can't even consider CS5 yet). That aside, I get reasonable conversion times with an older version of Lightroom -- about 20-25 seconds per RAW file.

Recently I downloaded and installed Lightroom v.3 beta 2 and did my first conversions with it last night. Big difference in performance -- roughly sixty seconds per file.

But could this have been a factor: for the first time I decided to try a DNG-only workflow to see how that would go. I started with about 20 RAW files and converted them to DNG (no compression, largest possible preview sizes, non-linear output).

It took a while to figure out that permanently storing edit settings within the DNG files themselves requires using Lightroom's "save to files" menu item -- otherwise, a file removed from the LR catalogue and imported again later won't retain its settings. Not having to use sidecar files seems -- at least in theory -- like a convenience. But the manual "save" is not so convenient. (If there's a way of also using .XMP sidecars with DNG files, I haven't found it yet. "Save to files" never seems to produce XMP files with these DNGs.) So, two questions:

Is there a way in LR 3 to have edit parameters saved within the DNG files, and have embedded previews updated in the background/on the fly, automatically -- not manually? (Refreshing/updating the DNG previews took a LOT longer than the "save to files" operation. But it was necessary if I wanted an accurate rendition of the updated images within, say, Photo Mechanic.)

Could the use of DNG format by itself have made any difference in performance during the export-to-TIFF operation? Or is output speed simply known to be lower in Lightroom 3 compared with earlier versions?
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madmanchan

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Lightroom v3 b2 and DNG files
« Reply #1 on: May 03, 2010, 03:08:33 pm »

Processing requirements have gone up for the new rendering algorithms such as sharpening, demosaic, noise reduction, etc.
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Eric Chan

NikoJorj

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Lightroom v3 b2 and DNG files
« Reply #2 on: May 03, 2010, 03:11:24 pm »

Quote from: Mike Arst
Is there a way in LR 3 to have edit parameters saved within the DNG files, and have embedded previews updated in the background/on the fly, automatically -- not manually?
To automatically store the edits, you simply have to tick the checkbox "automatically save changes to XMP" in the catalog Preferences dialog, Metadata tab.
They are stored within the DNG file, I don't know any way to generate a separate XMP sidecar for a DNG.

That command doesn't update automatically the embedded preview (doing so would generate too much waiting time for the preview to be rendered and then written after each slider change), so you have to do it manually at the end of the session (in Library, Metadata/Update DNG previews and metadata).

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Could the use of DNG format by itself have made any difference in performance during the export-to-TIFF operation?
I didn't test it extensively, but I don't feel the use of DNG files impacts significantly the performance vs the canon CRW files I normally use.
On the other hand, the beta of LR3 might well be slower (being a beta).
« Last Edit: May 03, 2010, 03:11:37 pm by NikoJorj »
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Nicolas from Grenoble
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Mike Arst

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Lightroom v3 b2 and DNG files
« Reply #3 on: May 03, 2010, 06:00:13 pm »

Quote from: madmanchan
Processing requirements have gone up for the new rendering algorithms such as sharpening, demosaic, noise reduction, etc.
I was pretty sure they had. These products always become more complex as they are improved. Still, going from 20 sec. to 60 sec. -- it seems excessive. I hope that some of this is due to the presence of debugging code. IAC the impending hardware upgrade will help. (And that's nuttin' compared with the performance of DxO Optics Pro on this machine: sometimes the conversion times run to three minutes; managed code is not always a blessing...)
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Mike Arst

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Lightroom v3 b2 and DNG files
« Reply #4 on: May 03, 2010, 06:04:37 pm »

Quote from: NikoJorj
To automatically store the edits, you simply have to tick the checkbox "automatically save changes to XMP" in the catalog Preferences dialog, Metadata tab.
Thanks. (As always, what I'm after is in the dialog box that I think I don't need to look in. :-|)

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They are stored within the DNG file, I don't know any way to generate a separate XMP sidecar for a DNG.
At the least I can write XMPs containing the IPTC data within, say, Photo Mechanic. But I doubt that'd include any LR-specific edit steps, which surely PM wouldn't be paying any attention to. (Note to self: see how the embedded preview differs from whatever can be pulled out of the DNG file via Photo Mechanic or via Michael Tapes' IJFR program...)

Thanks.
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john beardsworth

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Lightroom v3 b2 and DNG files
« Reply #5 on: May 04, 2010, 03:43:38 am »

I'm pretty sure that you can create XMP sidecars by making your DNGs read-only. It's pretty pointless though, as they don't contain all your metadata and you can't do anything with them (so they have no backup value).
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Mike Arst

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Lightroom v3 b2 and DNG files
« Reply #6 on: May 04, 2010, 07:29:44 am »

Quote from: johnbeardy
I'm pretty sure that you can create XMP sidecars by making your DNGs read-only. It's pretty pointless though, as they don't contain all your metadata and you can't do anything with them (so they have no backup value).
Getting the XMP file written by making the DNG file read-only seems like a mighty kludge-y way of going about it -- almost more like an convenient accident than a feature.

So even though XMP sidecars accompanying RAW files contain edits, the ones that accompany DNG files don't? That seems odd too. Anyway, it doesn't sound like DNG+XMP is worth pursuing.

Considering the need for the time-consuming step of updating the previews -- I was surprised it took so long; does each copy of LR come with a tiny artist whose only job is to do one-of-a-kind watercolor paintings of DNG previews? :-) -- this is definitely a "higher-maintenance" workflow. Haven't decided yet if it's worthwhile. The idea of leaving the original RAW files completely alone is appealing...but oh, those preview-regeneration times. Hell, for efficiency's sake it might be better just to make copies of the RAW files and work on the copies. Or shoot JPEG (I'm kidding! I'm kidding! :-).

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john beardsworth

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Lightroom v3 b2 and DNG files
« Reply #7 on: May 04, 2010, 08:02:56 am »

Quote from: Mike Arst
Getting the XMP file written by making the DNG file read-only seems like a mighty kludge-y way of going about it -- almost more like an convenient accident than a feature.

So even though XMP sidecars accompanying RAW files contain edits, the ones that accompany DNG files don't? That seems odd too. Anyway, it doesn't sound like DNG+XMP is worth pursuing.
It isn't. The concept of the DNG is to do without sidecars, so generating them is pointless and it's unsurprising the method is a kludge.

I did not say raw files' sidecars contain edits and DNG files' sidecars don't. They are identical. However, sidecar files do not contain all your metadata (eg they exclude history, stacks, flags, assignment to collections), and you can't import DNGs' sidecars back into LR to restore earlier metadata. So even if it were easier to generate them, they wouldn't be much use.

Updating the previews is most valuable when you use other applications to examine or output the images - they can grab the updated preview and output a rendition that includes your adjustments, and they can do so quickly.

John
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Mike Arst

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Lightroom v3 b2 and DNG files
« Reply #8 on: May 04, 2010, 02:45:44 pm »

Quote from: johnbeardy
Updating the previews is most valuable when you use other applications to examine or output the images - they can grab the updated preview and output a rendition that includes your adjustments, and they can do so quickly.
Yes, so I found out after not updating a preview and then looking at the same image in Photo Mechanic, which displayed the previous Lightroom session's edits (when I had updated the preview). This also seems to affect displays within LR itself -- say, if the image is removed from the catalogue without a preview update, then re-imported. Whether the simple 'save' option is used (writing editing data into the file), versus a full preview update, makes a difference in speed of display within LR is something I'll have to test. Meaning, whether LR displays the image faster the next time it is opened -- if the preview was fully updated during the previous session.

At one time the option to write changes to XMP automatically made the program unbearably slow. It was constantly writing in the background and would become unresponsive while it was doing so. It will be interesting to try this again in LR3 to see if the performance has improved. I would hope so. As I recall, the LR developers caught quite a bit of flak about it at the time...
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