The Digital Negative (DNG), pros & cons for its use
Adobe’s Digital Negative (DNG) file format
With the advent of digital photography a number of years ago, Adobe developed and created an open source publicly available specification called the Digital Negative or DNG for short. This was released to the public in 2004.
As camera manufacturers developed new cameras they often developed a new camera RAW file format presumably to bring the most of the camera body out. The reality is all camera manufacturers store the same information they simply choose to store it in a different format or order within their respective RAW file.
To give you a sense of just how many RAW file formats are out there just take a look at the below link. Canon has CR2, Nikon has NEF, Olympus has ORF, and the list goes on. There are however a handful of manufacturers who actually store their images as DNG files.
With such an exhaustive list of various camera RAW formats it’s easy to understand how much work Adobe has to continue to maintain it’s Camera Raw database in order to read the various file formats in their products, namely LR.
With today’s digital cameras there is an abundance of information that can be stored with the RAW file. Such metadata such as camera body, serial #, shutter speed, aperture, ISO, white balance, flash firing (or not), lens used, etc. Then after you as a photographer have downloaded your images you may add additional information such as your copyright, name, URL address.
Then comes along your image processing tool. I use Adobe Lightroom (LR). This allows me to catalog, keyword and develop these images. All this information is stored in LR and can be kept along with the RAW or DNG file.
If you are using a DNG file format any additional metadata including your develop settings are stored inside the DNG file itself. If however you are not using DNG and choose to continue using the camera manufacturer RAW file the additional metadata is stored in a separate sidecar file with an XMP file extension. So if you want to send a customer a processed RAW image you must remember to also send along the XMP sidecar file as well.
The first first two highlighted lines represent a Canon CR2 RAW file along with its associated XMP sidecar file. The next file is a DNG file containing exactly the same attributes (metadata, keywords, develop settings etc.) all contained in one file. You’ll also notice the DNG file is smaller.
So what are the advantages and disadvantages of DNG?
- DNG is a universally accepted RAW file format that is publicly available and can be read by all of the major image processing tools (LR, Photoshop, Affinity Photo, etc.). This allows for security knowing your image files will be protected in the long term. What happens if Canon decides to no longer support the CR2 RAW file that was used in the Canon 30D?
- There is no concern in buying new camera gear that supports DNG as you’ll have the comfort of knowing you can immediately process them in your tool of choice. Many times the Camera Raw support provided by software companies lags behind the availability of the camera release.
- File sizes are generally smaller.
- Additional Metadata is stored in the DNG file itself instead of in an XMP sidecar file.
- Using industrial strength image processing tools such as LR are available. Relying on camera manufacturer software to process your images is downright wrong. Why do we allow these manufacturers to hold us hostage to their proprietary RAW image formats? We should be able to use a standard DNG format should we choose.
- You’ll need additional processing time to convert your RAW files to DNG during LR import if you choose to do so at that time.
- Additional disk space required should you decide to convert to DNG and keep your original RAW file for archival purposes.
- Backups! Here is a big one for me. I have a Mac Pro with my LR database and images. I have a complete backup locally attached to my desktop in a Drobo. In addition I have a local QNAP TS-671 Pro NAS (network attached storage) located in my basement with a complete backup of everything including my multi-media centre data. This NAS is connected to a remote QNAP 451 NAS located at my son’s home some 800km away from me. When I go to make ANY changes in LR of keywords, tagging, develop settings, etc. the ENTIRE DNG file gets copied to my various backup devices including the remote NAS. If I remain with RAW files after the initial backup only the small 4K XMP sidecar file changes and needs to get backed up, thereby significantly reducing my backup times and data transfer.
Ready to convert?
If you want to convert your images to DNG there are a couple of easy tools to use. One is to use Adobe LR. While in the Library module click on the top “Library” menu item and scroll down to “Convert to DNG…”. I DO NOT “Delete originals after successful conversion” but rather archive them away in a new location. I also do not “Embed Original Raw File” as it then defeats the purpose of generating a smaller DNG file.
The other option is to use Adobe’s RAW Converter for Mac or Windows. As LR has the ability built in there is no need to download a separate application.
Now you might be asking yourself “I don’t understand all this because I shoot all my photos in JPEG”. Read our Understanding RAW article for more details.
So, what do I do? Right now I have a majority of my photos in their original RAW format. When a new version of LR is released I backup my Lightroom Library and ensure the XMP sidecar files are current. After I upgrade my LR version I immediately check to ensure that I have backwards compatibility to my old RAW files. If in the highly unlikely event that I don’t have backwards compatibility I would immediately restore my previous version of LR & catalog and decide what my next steps would be.
By remaining with the original RAW file I don’t have the additional overhead of converting to DNG and my backups are significantly faster.