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How to correctly see DNG files generated from Nikon NEF

PostPosted: Sun May 27, 2012 9:59 am
by mglienecke

with my typical workflow RAW (Canon or Nikon) -> DNG in Lightroom it all worked fine for Canon. With my new D800E and the NEF-files I use the new Lightroom 4.0 and suddenly I see neither the small thumbnails, nor the image as such (in Lightroom yes) when the DNG file is used. All is still fine for the "old" Canon DNG files...

Anybody having an idea what to change / do?

All the best

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Mon May 28, 2012 9:27 pm
by Axel
Remove the "fast load" option when exporting from LR4. When this option is enabled the files created are no longer DNGs (just an undocumented private format of Adobe that no one else can read to this date).

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Sun Jun 03, 2012 2:24 am
by Califdan
I'm having same problem although my workflow starts with Canon CR2 files. When I import them into LR4, using the "Copy as DNG" option the thumbnails in Windows Explorer just show the default. However, for those images that were converted to DNG using LR3 the thumbnails show properly.

I see the suggestion to turn off the "Fast Load" option as this renders the file not a real DNG. With all due respect I do not support this acertation, but that is not the point and can be left for another discussion. I did some testing and indeed you are correc that files exported from LR4 as DNG with the "fast load" option turned on do not display thumbnails whereas those with "fast load" turned off display properly. So, this brings up two quesitons:

1) How/Where do I tell LR to not include the fast load option on the DNG's it creates during import (when "copy as DNG" is selected.

2) Howcome DNG's Exported with LR3 can display the thumbnail no matter which option is chosen?

Thanks -- Dan

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Mon Jun 04, 2012 3:34 pm
by Axel
Well, DNG is supposed to be a proprietary but documented format. The latest published specifications, at the time I write this, is v1.3 from year 2009.

LR4, with the new fast load option, create files that no longer correspond to the published DNG specification. Fast-load is a Lightroom-only format. Call them DNGs if you like, but the format actually is something else, maybe close, maybe not so close, to the published DNG specifications.

Whenever Adobe eventually decides to publish a new specification, along with an updated DNG SDK, I will call those files "DNG" again. For the time being they are a proprietary, opaque and undocumented Adobe-only format.

The "lossy" option is even worse as the file's are no longer RAW, it's an Adobe-only JPEG variant, just as undocumented, opaque and proprietary.

Without those options enabled, LR4 emits files conforming to the published 1.3 specs and we and other 3rd-parties can read them just fine. Of course all versions if Lightroom before 4.0 were strictly DNG compliant so that's whay you don't run into any issue with the files created with these versions. I'm not sure exactly how to make sure this option is always off in LR4, maybe someone in Adobe's support forums knows the answer.

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Tue Jun 05, 2012 9:27 pm
by HotShot
Strangely, the new DNG 1.4 pics generated by LR 4.1 display properly in Explorer (explorer thumbnail + preview image) if the updated DNG embeds a full-scale preview image. With embedded half-size preview, or with "no preview" (actually only a very tiny preview, sth like 160x120px) the codec fails (= displays nothing).

From the information I gleaned through various Adobe- and thirdparty forums, the new "fast load data" is simply *another* preview image (i.e. in its own SubIFD). Exiftool reveals that, among other software. I guess that's why most non-Adobe software fail at rendering these new DNGs with a variety of SubIFD : they likely assume that the content of SubIFDs is Jpeg thumbnails/reduced resolution/preview images, but instead encounter some weird data stream. Probably the solution is to read and securely interpret the IFD structure prior to attempting any decoding of embedded previews, to make sure it skips the "strange part" and displays the "right part". That's why the folks at Adobe say something in the line of "any DNG-compliant software should still work"... provided they are aware they *must* skip some preview data.

Of course, given the untimely lack of a proper documentation / spec / SDK, that's still a bunch of wild guess and can certainly NOT provide a foolproof solution. (I harass the Adobe guys more or less daily, in the hope they'll understand that's definitely no proper way to release software)

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Wed Jun 06, 2012 10:33 am
by Axel
The solution is that Adobe need to actually document their supposedly documented proprietary format.

Re: How to correctly see DNG files generated from Nikon NEF

PostPosted: Wed Jun 06, 2012 11:31 am
by HotShot
That's why I keep being nasty. I've a hard time understanding their course of action regarding their DNG spec and software release policy.

I simply wanted to report on a temporary good news : LR4.1-exported DNG files with Fast Load and a Fullsize Preview embedded (this is not the default in a fresh LR installation, set on 'half-size' previews only) may display correctly with FPVCodec

(Axel, I've noticed your messages regarding this issue at several places, DPReview, Adobe... hope you did not take too much heat for that ; some guys there have at times a strange way of thinking :twisted: e.g. "stop whining about bugs" "it should work, so don't expect anything from us and shut up" "we shall do it as it pleases us, when it pleases us, if it pleases us, issue closed" or even "thanks for your bug report, we'll file it as a feature request or perhaps as idea suggestion", WTF?!)