DNG vs ARW

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henryk1 Senior Member • Posts: 1,073
DNG vs ARW

What, if any, is the advantage in converting .ARW files to .DNG? I use Lightroom Classic, and that seems to like .ARW files just fine.

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Pentax H1a, H3v, Spotmatic, MX, ME Super (2), KX, *ist DS, K10D, K20D, K-5, K-01, K-3, Sony A7Riii.

Jeff2013
Jeff2013 Veteran Member • Posts: 3,031
Re: DNG vs ARW
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DNG compresses the files, so they are smaller.

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OP henryk1 Senior Member • Posts: 1,073
Re: DNG vs ARW

Are the smaller files lossless?

Jeff2013
Jeff2013 Veteran Member • Posts: 3,031
Re: DNG vs ARW
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Yes, DNG uses lossless compression. I convert all my files to DNG when I import to Lightroom. The main disadvantage of using DNG is that some non-Adobe image processors do not recognize DNG files. A supposed advantage is that DNG files might be better supported in the future than proprietary format camera files (who knows?).

There are other advantages and disadvantages to using DNG. You might do a Google search to learn more.

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Jeff2013
Jeff2013 Veteran Member • Posts: 3,031
Re: DNG vs ARW

You list the Pentax Spotmatic as one of your cameras. Now that brings back great memories from when I purchased one in 1965 - my first real camera.

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jan pawlak Contributing Member • Posts: 664
Re: DNG vs ARW
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Imaging Edge Desktop, Sony's original RAW development program, cannot read dng files

jp

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PWPhotography Forum Pro • Posts: 10,809
Re: DNG vs ARW
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My understanding is that DNG is compressed lossless format but may lose a few camera related info that may not important however.

Personally I stay with camera OEM RAW as disk space is cheap these days.

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Trollmannx Veteran Member • Posts: 7,271
Re: DNG vs ARW

If you have a very good reason for converting ARW files to DNG then go ahead.

If not, stay with the ARW files.

In my case ARW files serve me well. No need to convert, that would just be wasted time, and as mentioned above, loss of information baked into the original file. And keeping both kind of files just in case seems a little bit odd to me.

But you are the boss, it is your files. 

OP henryk1 Senior Member • Posts: 1,073
Re: DNG vs ARW

Thanks to all. I think I'll stay with .ARW because that form works fine with Lightroom and I won't have to take the time to convert. I'm not a pro, just an aging amateur, so don't have to worry about future formats.

P.S. I wish I had never sold that Spotmatic. It was a joy to use.

Lan Senior Member • Posts: 2,475
Re: DNG vs ARW
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henryk1 wrote:

Thanks to all. I think I'll stay with .ARW

Good choice

One of the big problems with DNG (from my perspective) is that whilst a DNG can contain raw image data, they don't have to. DNG is a container format, and in addition to raw data, it can just contain JPEG and/or TIFF images. Theoretically you could just store JPEG image data in there, and it would still be a valid DNG file.

If you edit an image on a pixel level, and then save as a DNG, the likelihood is that you're getting baked demosaiced data in your DNG, and not the raw data you might be expecting to find.

If you're lucky the DNG file may also contain the original raw file as well, as it does have an option to embed the original raw file, but then your file sizes will be somewhat bigger than they might be...

From an archival perspective, any format which is adequately documented now, (i.e. ARW) should be possible to open at any time in the future. If you're worried, save a copy of source code of something which can open and process the images now; i.e. the source for libraw; which is free, and takes up just 1.5MB, which is far less disk space than you need to store a single camera JPEG, and should allow you to read the format at any time in the future:

https://www.libraw.org/download

Libraw can currently read up to A7M3, A9M2, and A7R4 (and most older Sony/Minolta cameras that shot raw).

Mark2d Forum Member • Posts: 61
Re: DNG vs ARW
3

I used to convert all my images to DNG with the thought that all edits to my RAW files from LightRoom could be contained in one file, that is, no sidecar. I thought it sounded simpler.

The downside (I realized much later) was that any edit to pictures in LightRoom would cause those DNG files to change... and when I ran my backup program, it would have to rewrite all the DNG files that had changed. If I had a heavy session of edits, this could run into the thousands of large files. Those backups were slow.

I quit doing that, and now just use the RAW Sony files with the sidecar file. When I do a backup, it's usually very fast, because those sidecar files with the development instructions are very tiny.

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