Convert to DNG?


Today’s Question: I use Lightroom and Photoshop and just bought a new Nikon camera. I can now shoot Raw format pictures. Since there are many Raw formats from the various Camera manufacturers and they are “non-standard” would you recommend converting to DNG format on import to Lightroom? What are the Pros and Cons of standardizing on DNG?

Tim’s Answer: The Adobe Digital Negative (DNG) file format was created as a publicly documented file format that can effectively replace the variety of proprietary RAW capture formats that have been created by camera manufacturers. In fact, a variety of digital cameras allow you to use the Adobe DNG format as an in-camera capture format to replace what would otherwise be a proprietary RAW capture format.

I don’t personally convert my RAW captures to DNG, for a few reasons.

First of all, despite the fact that there really aren’t any “real” reasons I should feel this way, I don’t feel comfortable deleting my original RAW captures after converting to the DNG file format. That means I would actually be increasing the amount of storage space used by my photos, since I would be keeping two copies (at least) of each image.

I also make use of a synchronization solution for backing up my photos (which I covered in an article in the September 2014 issue of my Pixology digital magazine). With this approach, the DNG file format represents a disadvantage when it comes to backing up my images. Any changes to metadata for a DNG file means the file itself is updated, and so the entire DNG file must be backed up again. With my approach of retaining the original RAW captures and saving metadata out to XMP “sidecar” files, the backup only needs to copy the small XMP file when I make changes to metadata for a photo.

In addition, I prefer to retain the “private” metadata that many digital cameras write into RAW captures. Granted, that data can generally only be accessed by using the RAW processing software from the camera manufacturer, but I like the idea of preserving any of that information just in case it becomes useful at a later date. It is possible to embed the full RAW capture in the DNG file to work around this issue, but that would also result in a rather large file compared to my original RAW captures.

There are, of course, some advantages to the DNG format. To begin with, as noted above, the DNG format is publicly documented, so that if the proprietary RAW capture format you would otherwise use is one day no longer supported by any software, you could still feel confident that the DNG format could be processed, even if new software had to be created based on the public file specification. This isn’t something I feel is of any significant concern, but some photographers feel differently.

Some photographers also prefer to have their metadata updates written into the single DNG file, rather than having those updates saved in a separate XMP sidecar file. As noted above, because of my approach to backing up my photos, the XMP approach is actually a benefit for me.
The DNG file format also provides a workaround for using software that doesn’t support the latest RAW capture formats. For example, perhaps you are using Adobe Camera Raw to process your RAW captures, but have an older version that doesn’t support a new capture format. You could use Adobe’s free DNG Converter software to convert those RAW captures to the DNG format, so they can then be processed with your older software.

Finally, the DNG file format produces files that are generally smaller than the original RAW capture, without actually losing any information, thanks to lossless compression. In general you can expect a DNG file to be about 20% smaller than the original RAW capture, though your specific results may vary.

Ultimately it is up to each photographer to choose whether a conversion to the DNG file format makes sense to them. I prefer to make use of the proprietary RAW capture format employed by the cameras I photograph with. But if your camera supports the DNG format, you could certainly use DNG as a capture format. And a variety of software tools allow you to convert to the DNG file format. The key is to consider the various advantages and disadvantages based on your specific workflow needs.