M 240 Lightroom DNG Imports - "Copy" or "Copy as DNG"?

[STB]

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As Lightroom users know, the import options are to copy one's RAW files or to copy them and then convert them to DNG.

 

Given that the M 240's RAW format is DNG, one might think that the right choice is to import by simply copying the files.

 

However, Martin Evening, in Lightroom CC/Lightroom 6: The Complete Guide for Photographers (2015), says the following (at Location 1395 of the Kindle version):

 

 

Although there are now cameras that support the DNG format, such as Leica and Pentax, it can sometimes still be worth converting DNG capture files to DNG in Lightroom, specifically to take advantage of the way Adobe programs convert to DNG.

 

Unfortunately, Evening makes this statement without elaboration (unless he elaborates elsewhere in the book in a passage that I am unable to find). Does anyone know what he is driving at? What are people's views on this question?

 

Thanks

Edited May 7, 2016 by STB

[Exodies]

Is it something to do with the "linear image" option? 

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[elmars]

With copy as DNG You convert the picture to the newest DNG-Version. The DNG-Version of the M is an older one. But I forgot the differences.

 

 

www.elmarstreyl.de

[STB]

With copy as DNG You convert the picture to the newest DNG-Version. The DNG-Version of the M is an older one. But I forgot the differences.

 

 

Thanks,

 

That might well be Evening's point, or at least part of it.

 

I just ran Paul Harvey's exiftool on a recent photo (from the terminal, the command is: exiftool -s myphotofilename) which reveals that the DNG version on my M 240, purchased new at the end of 2013, is 1.3.0.0. In September, 2012, Adobe published 1.4.0.0. According to Wikipedia, the differences are as follows:

 

 

 

1.4.0.0, published Sept., 2012 This version added Floating Point Image Data, Transparent Pixels, Proxy DNG Files, and additional tags. It also added SampleFormat and Predictor.

 

If I can figure out a way to identify whether a DNG file reflects one or more of these features, I'll do some follow-up testing. One quick way might be to make a photo and import it both as "Copy" and as "Copy as DNG", run exiftool, and see what, if any, differences there are in the tags.

 

Or maybe I'll try to send a note to Martin Evening and ask him what he means

Edited May 8, 2016 by STB

[ramarren]

None of the things in DNG Specification v1.4 will be in original files from a camera device unless that camera device already produces v1.4 files. 

 

One reason to use Copy with DNG Conversion with some camera's DNG files is that most camera devices do not include DNG lossless compression so using DNG Converter or "Copy with DNG Conversion" can apply that compression and save space in your raw file archive. For example, an uncompressed DNG file from the SL is about 43Mbytes in size compared to a converted DNG of the same file at 24Mbytes. You can set other parameters such as inclusion of fast load data, smart preview data, etc. Also, the color calibration profile, etc, in the generated DNG file is Adobe's standard, not the default (which is poor quality). 

 

But if you want to keep your originals original, there's no real need to use the conversion. 

[STB]

None of the things in DNG Specification v1.4 will be in original files from a camera device unless that camera device already produces v1.4 files. 

 

 

Notwithstanding its name, exiftool can be used to read a good deal more than a camera's original file.

 

Your comments are interesting, but I'm not sure how relevant they are to the question of what the difference is between simply copying a Leica M 240 DNG file in Lightroom and copying one as DNG.

 

For example, with respect to compression, one can choose DNG compression in the Leica M 240 camera menu. Smart Previews, which can be generated at any time, and not only for DNG files, would not appear to have anything to do with DNG conversion. Nor would Camera Calibration > Profile appear to be relevant, given that both Adobe Standard and the embedded profile are available regardless of whether a Leica M 240 DNG file is simply copied or copied as DNG.

Edited May 8, 2016 by STB

[ramarren]

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Notwithstanding its name, exiftool can be used to read a good deal more than a camera's original file.

 

Your comments are interesting, but I'm not sure how relevant they are to the question of what the difference is between simply copying a Leica M 240 DNG file in Lightroom and copying one as DNG.

 

For example, with respect to compression, one can choose DNG compression in the Leica M 240 camera menu. Smart Previews, which can be generated at any time, and not only for DNG files, would not appear to have anything to do with DNG conversion. Nor would Camera Calibration > Profile appear to be relevant, given that both Adobe Standard and the embedded profile are available regardless of whether a Leica M 240 DNG file is simply copied or copied as DNG.

 

 

All true, but part and parcel of what LR can do as part of the DNG conversion, depending upon how you've set the DNG conversion parameters. 

 

Examining an original DNG and a converted DNG with EXIFtool shows a good number of changes in the representation of the raw file metadata. The converted file looks and works no differently compared to the original file, in general; it may load faster, it may take up less disk space, etc. But there are many ways to represent the metadata in a DNG that are equivalent. Whether any of them have a noticeable benefit (or detract from the file) is often quite hard to determine. 

[STB]

I have the feeling that it would be helpful at this point to try to send an e-mail to Mr. Evening. Perhaps he will be willing to elaborate.

Edited May 8, 2016 by STB

[ramarren]

I have the feeling that it would be helpful at this point to try to send an e-mail to Mr. Evening. Perhaps he will be willing to elaborate.

 

 

I haven't written Martin for some years now. Just sent an email, let's see what he says. 

[ramarren]

Martin responded quickly, as usual: 

 

 

On May 9, 2016, at 3:35 AM, Martin Evening <martin_evening@me.com> wrote:

 

Hi Godfrey,

 

Basically, the DNG spec is made freely available to developers. However, that does not necessarily guarantee that if a third-party developer uses the spec to make their products DNG-aware or DNG compatible that they will do so effectively. There are known instances where DNG files can’t be read correctly. For example, the latest version of Capture One Pro can’t read HDR DNGs exported from Camera Raw/Lightroom and you can’t use Capture One to read DNG files converted from non-supported cameras. 

 

With regards camera-generated DNGs, I don’t recall mention of any specific problems with Leica cameras. In general, there are no known problems to do with camera-generated DNG files being of inferior quality or more prone to corruption. The benefit is more to do with obtaining better compatibility with Adobe software. A camera-generated DNG can be read just fine, but an Adobe converted DNG may well save the raw data more efficiently. Using the later versions of Lightroom, the DNG conversion ensures full DNG support. For example, the addition of a DNG hash that can be used to check and validate raw data. Also, with later versions the DNG conversion creates tiled DNGs with fast load previews, which can both speed up the raw processing.

 

Regards,

 

Martin

 

I take this to mean as I wrote above: There are equivalent ways of constructing a DNG file from the same camera output data and specifics of the way Adobe constructs a DNG file from the out-of-camera DNG data may have some advantages in loading speed, size, etc, when using Adobe software.