If DNG Can Read My Files, Why Can't Lightroom?
You just bought a new camera and discover that you can't read the image files is records. Not to worry, downloading the free DNG Converter from Adobe will save you from having to pay for an upgrade to Photoshop and Lightroom. That sounds easy enough. Really?
For the uninitiated, DNG stands for "Digital Negative," and is a file format invented by Adobe. One of their stated but lofty goals at the time was to promote DNG as a "universal" camera raw format. A few cameras have been released over time that can natively save files as DNG, but most major camera makes have pretty much ignored DNG. It's a turf war you see.
Whereas most people only need to be able to read files from cameras they and perhaps their friends own, Adobe has to be an expert at every brand of raw format. They had to be. No one would use Photoshop or Lightroom if it couldn't read images shot with their camera. Even if they never created Adobe Camera Raw, they had to deal with the problem. So long as photographers were forced to use their brand's proprietary raw converter, many would conclude they didn't need Photoshop too. So, to keep their users within the fold, they needed their own raw converter. And as a Nikon user who was forced to use the abysmally bad Nikon plugin in the pre-ACR days, I applaud Adobe for taking on the challenge. ACR allowed users to work with all their raw files in a uniform and streamlined way, even if they owned cameras from more than one brand.
It turned out, Adobe was so successful at convincing users to standardize on ACR, they began viewing it as a competitive advantage. They decided to use it as leverage. If you wanted to get access to each successive major release of Adobe Camera Raw, you had to upgrade your copy of Photoshop. So as not to seem completely evil though, they also released a free, standalone DNG converter. As a roundabout solution, you could use the DNG converter to create DNG versions of each of your original camera raw files, and then open them in ACR. Adobe would still let you use their raw conversion technology for free, but they didn't want to make it that easy for you unless you paid.
Think about it. By the time Lightroom hit the scene, Adobe offered three ways to read raw files. We had Photoshop (via Adobe Camera Raw) and Lightroom, each of which offered minor upgrades for free, right up until the time the next major release came out that you had to pay to upgrade to. And then there was the standalone DNG Converter, a download product that has continued to be upgraded for free ever since the beginning. You and I know that at their heart, all three of these products use the same core conversion code. But two periodically cost to upgrade, while the other has remained free. So long as you never upgrade your camera, you can remain blissfully ignorant of this confusion. But if you hadn't kept up with your Adobe upgrades, you could find that your trusty old Adobe application couldn't deal with your new camera files.The latest version could do it, but you never paid to upgrade.
Setting aside concerns over the added inconvenience though, the DNG Converter does a pretty good job. Larger embedded previews can make images seem to load almost immediately. The format itself is increasingly recognized and recommended format for archiving images. The raw data is saved with a lossless compression algorithm making them (in at least some cases) significantly smaller than the originals, and DNG files can be checked to ensure their integrity via a checksum.
Adobe insists that nothing is lost in the conversion to DNG. It is possible that certain proprietary camera data may not survive, I'd judge that to be rare, and any camera maker attempting to muck things up this way would likely regret it. If the DNG converter can't read it, then Lightroom and Photoshop ACR wouldn't be able to either. And these days, Lightroom is ubiquitous. Still, I'd recommend keeping your original camera raw files safely stored away somewhere, just in case. The DNG Converter offers to embed them in the converted DNG files, but I'd advise against it. Why bloat your working DNG files with all that extra data? Most of the time, you shouldn't need, so it seems best to keep things separated.
Your converted DNG files won't be locked into just ACR and Lightroom either. DNG is an open specification and, although not widely supported in non-Adobe applications, it has continued to gain adherents. At this point in time, it is the closest thing we have to a "universal" raw format.
Periodically, the DNG specification has been revised to add new features or improve some aspect of the prior version. The latest I believe it 1.4, having been released in 2012. Among other things, this version added the ability to store floating point numbers (instead of only really big integers) to support Photo Merge HDR.
As a curious side note, the name "Digital Negative" is actually a bit of a misnomer. In some ways, any raw file can be thought of being somewhat similar to a traditional film negative in that both require specific processing to transform the recorded latent information into a useable image. But a Digital Negative image is a positive image, not a negative. The data represents brightness and saturation of color as tallied by the photosites built into the camera sensor. Brighter, more saturated areas are represented by greater values, not the reverse as would be implied by the "negative" moniker.