DNG vs. proprietary raw format

I’m just getting started scanning negatives with my Pentax K-5 and processing with NLP. I’m in the habit of saving images in the proprietary Pentax PEF raw format, but the camera has the option to save DNG files instead, and of course I can convert existing PEF files to DNG.
NLP seems to be able to handle either file type. Any advantage to using DNG vs PEF?

Hey there – Welcome to the forum!

DNG files are the prefered file type for Lightroom to work with. The main difference is that conversion/editing data will be saved all in one file (the DNG), while with the native PEF format Lightroom will create a second file holding the metadata (XMP file).

I’m seeing the same behaviour with keeping my Fuji RAF files, like here: https://chris.bmonkeys.net/i/4km3e27.jpg

Other than that, there’s no difference.

Thanks for your helpful reply.

I’ve been using Pentax PEF raw files in Lightroom for years (and Sony ARW raw files before that). I have the XMP sidecar file option turned on in LIghtroom (Edit / Catalog Settings, check box for “Automatically write changes into XMP.”

When I make an NLP change to a PEF file, the PEF file is unchanged but the XMP file is updated, and I can see NLP information in the XMP file.

When I make an NLP change to a DNG file, the DNG file changes. When I look at the metadata of my NLP processed DNG file with exiftool, however, I don’t see anything related to NLP, although it must be embedded in the file in some way that exiftool doesn’t show.

I kind of like the idea that the PEF files never change - less chance of getting corrupted?

I’ll keep thinking about it.

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You can set Lightroom Classic to write XMP data into the DNG file or not in catalog settings. Lightroom always stores the XMP data in the catalog itself, you select if you want to write it to the file (DNG). Not sure if it applies to proprietary file types though. You can also save the XMP data into a separate XMP file with the same name as the photo. Get sort of messy if you ask me and so far I have not seen a corrupted DNG file and I have over 30,000 of them in Lightroom.

As far as picture quality, no difference I have ever seen. There is a possibility using Pentax SILKYPIX Developer Studio may do something more with the PEF file, but If you already use Lightroom, SILKYPIX is a huge step down.

I think it comes down to the fact that it doesn’t really make any difference. I’ll probably just keep doing what I’m doing.

I tried SILKYPIX once when I first bought the Pentax, but have nevver used it since. I agree it doesn’t compare to Lightroom.

Thanks again for both or your responses…

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In the case of Pentax, there has often been market cynicism that says they included the DNG option because they were such a minor player in the market that their future is uncertain. DNG is an “open” standard format, but PEF is not. So if Pentax goes away… DNG will preserve your raw file edit-ability.

That said, you might want to run a few tests to see whether there is any discernible quality advantage to using either format.

No matter if DNG is an “open format” or not: it’s far more often supported by imaging software than PEF. Most halfway decent photo editors should however support PEF.
Here’s what I think: converting your already existing files to DNG is not necessary and actually the conversion can potentially deteriorate the photos. There have been issues with a certain Lightroom version, when it came to converting Canon RAW files to DNG. Many people did that and threw away their original RAW files. The bug got fixed at some point, but any issues with the converted images couldn’t be repaired. It would be surprising if the PEF to DNG conversation was broken in some way, but you never know. If we’re already talking about leaving the RAW files untouched, this would be the first thing: don’t convert your PEF files to DNG. However, what I would do is switching the RAW format to DNG in camera. I have a K-5 and a K-3 II and both of them are set to DNG. The cameras know how to properly write the image data to DNG right away and you will end up with a consistent and very well supported file format. If the camera supports DNG I don’t see why not using it.
About the editing steps being stored in the DNGs or not: I finally switched that feature on in Lightroom. Of course there is a small risk that rewriting a RAW file will corrupt it, but I see the risk as not critical. I never had any issues with that. Just let Lightroom write back all changes and don’t kill the process in the middle. It’s nice to have all the edit steps in the catalog file, but that is about 2 GB in my case and gets rewritten all the time. The risk that this catalog file gets corrupted is much higher than all RAW files will. I rather want to have my editing steps be stored in each file, so in the worst case (catalog file corrupted) I can import the files into a new catalog and the edits are still there. Also viewing the files in Adobe Bridge will show the keywording, rating, etc. But the same thing works with PEF of course - and you will have the XMP sidecar files for each photo. But then it can easily happen that you move files somewhere else with a software that only shows the photo images and all of a sudden the sidecar files are no longer avaliable at the new location. That’s why I prefer having the edit information in the DNG files. It’s all in one place and cannot get lost. I hope that helps. :wink:

My assumption has been that even if Pentax went away (I hope not!) I could still convert PEF files to DNG using Adobe’s conversion tool.

Another of my assumptions is that a DNG file, whether created in the Pentax camera or by Adobe’s converter, contains exactly the same raw data as the PEF file, although arranged differently.I’m still getting set up to scan more than the few negatives I’ve scanned with the camera. I’m waiting for Negative Supply carrier and light source to show up and building a copy stand, but I’ll do some comparisions once I scan some more.

Up until now I’ve been scanning with a Nikon Coolscan V, which does a great job, but it’s slow.

I can see arguments on both sides. Ironically, the less difference it makes, the harder it is to decide.

Makes sense. Let us know what you learn.

Bill Burkholder