The Adobe Digital Negative (DNG) format started out as an open file format for saving raw image data from the sensor in a digital camera. While DNG hasn’t exactly become a household name, its inherent versatility has recently brought DNG into wider use behind the scenes in several Adobe and non-Adobe photo workflows, and not just for camera raw files. Are you already using DNG without even knowing it? Let’s find out.
Why DNG Was Born
Visit the user forums for Adobe Camera Raw, Lightroom, and other applications that edit camera raw images, and you’ll quickly come across one of the most common questions: “When will your raw editor support the new camera I just bought?” Camera raw format is popular because it preserves more original image quality than the more common JPEG format, although a raw file takes up more storage space. Cameras usually save raw files at 12 to 16 bits of tone and color information per pixel typically using lossless compression, while they save JPEG files at just 8 bits per pixel with lossy compression.
But camera raw is actually not a single file format; the data is unique to each combination of sensor and camera. When a new camera comes out, everybody who makes raw editing software must figure out the new camera’s raw format and add it to their applications (camera makers don’t often share the details of their raw formats). It’s an ongoing cycle no one enjoys: New cameras have new raw formats, software developers have to update their applications to keep up, and buyers of new cameras end up waiting for those updates.
To try to simplify raw format support for everyone, Adobe designed Digital Negative (DNG), a way to store raw sensor data as an open, royalty-free format with no licensing requirements. Compared to proprietary raw files, DNG offers benefits such as rich support for metadata, previews, and file integrity checks. The idea was that if cameras and software standardized on DNG as a common camera raw file format, editing software could open the raw files from new cameras without needing compatibility updates. Beyond that, some DNG features appeal to libraries and historical archives, which face major challenges in maintaining the integrity and readability of digital assets as proprietary formats grow in number.
Young DNG Tries to Get Attention
Adobe made sure its professional imaging applications supported DNG. For example, Adobe Camera Raw and Adobe Photoshop Lightroom have DNG options in their Save and Export dialog boxes, respectively.
But the ideal of a single universal raw file format hasn’t quite become a reality. Although some cameras by companies such as Pentax and Leica can save camera raw images as DNG, most camera companies stick to their own proprietary raw formats. Adobe provides a free DNG Converter utility and builds DNG conversion into Camera Raw and Lightroom, but busy photographers tend to decide that the benefits of DNG aren’t worth the extra time to convert thousands of proprietary raw files to DNG.
In the photography community, you typically hear DNG described as a format that never really took hold as an open replacement for proprietary camera raw formats, and many assume that the discussion ends there.
But if you look at emerging photography workflows, you’ll find that DNG is enjoying a renaissance in unexpected directions.
DNG Grows Up, Starts a Family
Adobe designed DNG to be a flexible file format. DNG can be a container for different kinds of image data (not just raw), partially processed raw images, and instructions for processing raw images. That all sounds dry and academic, but the real value of those capabilities started to appear as Adobe upgraded their photo applications. When Adobe added the ability to merge multiple raw photos into panoramic or HDR images in Camera Raw and Lightroom, some didn’t think this was significant because Photoshop already creates panorama and HDR images. But in Camera Raw and Lightroom, a panoramic or HDR image is produced as a DNG file, stored in a near-raw form that you can edit with the superior flexibility of raw development controls. That’s a major advantage over the images saved by Photoshop and other applications. For example, you have much more control over adjusting white balance and highlight recovery for a DNG panorama than for a panorama merged into a TIFF or Photoshop file.
In software such as Camera Raw, Lightroom, and DNG Converter, Adobe added DNG output options such as Fast Load Data to open DNG images more quickly, and DNG compression to reduce storage needs while preserving nearly all of the original image quality. For example, Lossy DNG can be useful when you shot 500 images for a magazine cover knowing that just one would be used; the 499 other images that might never be used could be archived at near-perfect quality using Lossy DNG to save a lot of storage space.
For Lightroom users, Lossy DNG is the basis for the Smart Preview proxy technology that lets you work on images when, for example, you want to edit a set of photos on a laptop away from the drive containing your full-size original files. Smart Previews preserve almost all the flexibility of raw editing, with much smaller files.
Useful as these features might be, they didn’t move the needle very far for general adoption of DNG. But the story wasn’t over yet.
DNG Matures Through Mobile Workflows
Many think of Adobe Creative Cloud as a subscription service for desktop applications, but another big part of the Adobe vision for Creative Cloud is a set of mobile applications with rich connections to desktop applications. For Adobe photography apps, DNG is now a fundamental, yet practically invisible, way to efficiently sync images among apps.
The value of DNG online emerged with the Lightroom Mobile apps and the Lightroom Web browser-based image editor and service. You can sync Lightroom CC images from your desktop or laptop computer to an Adobe cloud server so that you can edit those images at another location by using a mobile app or a web browser. But original image files can be large; how could perhaps thousands of big images be synchronized efficiently over bandwidth-constrained networks and on mobile devices with limited storage?
Adobe already had the answer: Smart Previews. Based on Lossy DNG, Smart Previews allow high-quality raw-based edits using less data than syncing an original raw file. All Adobe had to do was put Smart Previews into the cloud. Smart Previews are now used to synchronize remote edits of raw and processed originals through Lightroom Mobile on Adobe cloud servers.
Adobe CC mobile apps are increasingly taking advantage of DNG. Like Lightroom on the desktop, the recently added HDR feature in the Lightroom Mobile app merges multiple raw exposures from your phone camera directly to a DNG HDR file. That DNG file is synced back to the desktop, where you can edit it more precisely if you want.
In the Photoshop Express app, if you use the new ability to send an image to Lightroom Mobile it syncs a space-saving Smart Preview. For my limited mobile data plan, that’s a good thing.
The Double Life of DNG
In desktop-based photography workflows, the continuing obstacle to wider adoption of DNG is the extra and lengthy conversion step that’s required, because most popular digital cameras don’t use DNG as their raw file format.
But there is another market where DNG has found a way to take root and thrive, by being in the right place at the right time. Both the Android and iOS mobile operating systems recently started supporting raw format photography — smartphone cameras are no longer limited to saving JPEG images. Unlike the camera industry, smartphone makers don’t have much interest in locking customers into proprietary camera raw formats. Instead of developing their own raw formats, both Android and iOS chose an existing open solution: DNG. When you use one of the Android and iOS apps that support raw capture, chances are it will use DNG as the format for the saved raw image. DNG has effectively become the standard format for raw capture on mobile devices.
Today, the story of DNG has two contrasting sides that are both true. In professional desktop-based photography, proprietary raw formats still rule while advocates of DNG continue to hope that it might someday achieve wide adoption. For mobile devices, DNG is already the default file format for raw capture on both major mobile operating systems and is a key part of Adobe photography workflows. Mobile devices sell in volumes so much higher than dedicated cameras that it may be through mobile photography that the role originally envisioned for DNG might finally become fully and widely realized.Tags