Last Updated on March 9, 2022 by Devaun Lennox
Photographers often ask about the best file format, which usually starts the RAW and JPEG debate. Yet, there’s another question that you may have recently stumbled upon. And that question is, what exactly is the difference between DNG and RAW files? Is there even a difference?
Well, yes. And there are quite a few differences, despite both of these file formats serving the same core function. So, in this post, we’ll tackle these differences in-depth. And ultimately, help give you some practical insights into which format is best for your workflow.
Jump to a Section
What Is a RAW Image?
Let’s start by talking about what a RAW file is.
A RAW file is your camera’s native file format containing all of the unprocessed data from its sensor. But, contrary to what many think, the RAW file isn’t a visual file format. Instead, it’s a raster file with RAW data of the analog-to-digital conversion process. Or put another way, it’s the values your camera recorded as it is converted light to voltage.
Light enters through the lens, reaches the sensor, then strikes the photodiodes on each pixel. When that happens, the camera converts the recorded intensity into an electrical charge using its processor. And it records each pixel across all of the 24 megapixels on the sensor, or whatever its resolution is. It then combines all of these values into an uncompressed readout, encoded as binary data (ones and zeros) into a single file.
So, in the end, a RAW file really stores data, not a picture, per se. And it merely contains information about how much light was recorded in either the red, blue, or green color spectrums, over the time of an exposure.
As such, a RAW file isn’t something we can view directly with our eyes, as it’s binary data. And that’s why it inevitably requires conversion to an actual visual file format like JPEG, TIFF, or PNG. And that also explains why it requires photographers to do some post-processing. But, to make things easier in the field, camera manufacturers include a full-sized JPEG preview thumbnail that accompanies each RAW file. And that lets you view the captured image in the viewfinder or LCD.
Overall, though, since the RAW file is uncompressed data taken directly from the camera’s sensor, it’s entirely unprocessed and doesn’t have any sharpening, saturation, or contrast applied. And it also stores the most detail and image data of all raster file types, making it a common choice amongst digital cameras, image scanners, and even film scanners.
The basic idea with RAW is to give photographers the most detail and freedom to control how the final image appears once it’s processed. But, it’s important to point out, though, that each RAW file is proprietary to both the manufacturer and the specific camera model. And camera makers do this as a way of showing ownership of the file.
The unfortunate result is that each camera requires a compatible software and processing engine to interpolate or reverse-engineer the data for viewing. Otherwise, you cannot view the data and thus edit the photo. And that adds an unnecessary level of inconvenience to this format that only benefits the camera maker, not the photographer or editor.
Below are the names of each of the proprietary file formats used by today’s camera manufacturers.
- Nikon — NEF/NRW
- Canon — CRW/CR2/CR3
- Sony — ARW
- Fujifilm — RAF
- Panasonic — RW2
- Olympus — ORF
What Is a DNG Image?
Now let’s cover what a DNG file is.
I mentioned above that RAW files are camera manufacturer and even camera-specific. That means they’re all slightly different, despite having the same overarching file extension name attached at the end, say Sony .ARW. And in 2004, Adobe found the influx of new undocumented RAW files quite frustrating. So much so they launched the Digital Negative (DNG) file specification that year developed on the TIFF 6.0 format.
Like, RAW, DNG is an uncompressed raster file that captures all of the sensor’s information at the time of exposure. Doing so ensures that you capture the maximum image quality your camera provides. However, unlike most RAW formats, it’s an open-source alternative, so anyone can use it without paying a licensing fee. And it’s generic and highly compatible with most editors, unlike traditional RAW files, which require dedicated software support.
The intention was to encourage camera makers to adopt the format and offer it as an option or, even better, the default file format in-camera. Doing so would standardize it amongst the camera industry and level the playing field. Crucially, it would also eliminate the proprietary technologies used to capture the RAW format. And that would also solve key compatibility issues, like forcing developers to constantly update editors with each new camera release, which usually takes several months.
It would also cement the idea that any developer who adopted the format could create software to help photographers access their DNG images, say, if Adobe went out of business. So solving these issues was a big win for Adobe.
And, of course, we can’t forget that it would start a new area of domination for Adobe, which surely would have been lucrative. And indeed, it would also make it easy for them to update their development software for each new camera, saving time, effort, and money.
But that didn’t happen.
And sadly, the DNG file format isn’t standardized today. Instead, only a handful of manufacturers offer it in-camera, namely Sigma, Ricoh, Hasselblad, and Leica. For everyone else, including the key players like Nikon, Canon, and Sony, you’ll have to use a DNG converter to unlock its benefits. Thankfully, you can convert most RAW files immediately upon import in Lightroom or use Adobe’s free DNG Converter. So at the very least, it’s a straightforward process.
Advantages of DNG
So why convert to DNG? Well, there are practical reasons to do so. But, these file formats also have their disadvantages, despite them both fundamentally being RAW files. So, let’s clear up the confusion so you can understand which will best suit your workflow. And let’s first start by covering the advantages of DNG.
Archiving & Future Compatibility
When it comes to archiving your old photos, DNG files are more recognizable and accessible than RAW. This format is also open-source so that any software company can establish support for it in the future. This is great news. Now, the reason that you have better third-party compatibility with the DNG format is because they don’t require a proprietary decoding algorithm to interpolate the RAW data into its visual representation. Thus, they have broader support amongst other third-party photo editors, not just Adobe’s Creative Cloud suite.
For example, GIMP and Darktable support DNG’s, and they’re free. There are also many paid editors like Affinity Photo, Capture One, Exposure X6, DxO PhotoLab, and ON1 Photo RAW that support the format too. As such, the DNG format becomes a better long-term safe bet if your camera company goes out of business. At least, if that were to happen, you wouldn’t lose support for your older RAW files and have difficulty opening them, like what Kodak has done with their files.
A good analogy is to think of RAW files as data on a floppy disk and DNG files as data on the cloud. The floppy disk requires specialized accessories to work, but the data on the cloud is easily accessible if you have a working computer. Therefore, DNG gives photographers peace of mind, regardless of the age of their files.
Built-in Checksum Validation
Unlike a RAW file, DNG files have an embedded checksum. So converting an image to DNG starts a rigorous checklist to validate its authenticity and spot image data changes that corrupt images. And that’s great news if you’re worried about dealing with a corrupt RAW file, so now you can have peace of mind during the image culling process.
You can also run this validation script across an entire library of images, making it incredibly easy to stop corrupted files. And it’s a must if you’re moving a library from one storage source, say your computer, to another. Granted this process doesn’t prevent corruption itself. But, at least it provides a tool you can use to spot it when it happens.
The DNG format is more compact than RAW, and merely converting a RAW photo can provide a 15-20% reduction in file size, depending on your camera model. Yet, they maintain the same image quality and also include a medium-quality JPEG preview.
There’s even an option to apply lossy compression and remove the JPEG preview altogether, further decreasing their file size. Together, the smaller file size makes this format ideal for storing large archives or situations where your computer’s limited on storage, as it requires less space.
It’s essential I mention the edits you make aren’t actually stored in a RAW file. Instead, RAW files have a sidecar, a separate (.XMP) file containing all the settings, changes, and edits. This is great since it means the original file is untouched. But, it also means every edited RAW file gets stored as two separate files. And that, in turn, complicates how easily you can edit the files later, as you’ll need the XMP file to recall any previous edits. With DNG files, the edits and changes get written into the file itself, leading to fewer files to store and manage. And it also makes editing the photo easier, since the changes are stored internally.
Disadvantages of DNG
While there are advantages to DNG, there are some notable disadvantages too. Let’s cover those now.
Time Consuming File Conversion
Arguably the most crucial downside is the amount of time it takes to convert from RAW to DNG. Since most cameras don’t shoot DNG natively, this format nearly always requires tackling the conversion process. Thankfully, Adobe Lightroom can do this automatically during import. It’s just a matter of enabling the option.
Even so, depending on your computer’s processing speed, the number of files to convert, and your camera’s resolution, it could take a significant amount of time nonetheless. Most files take 10 seconds or less to convert. But that 10 seconds adds up if you have a shoot with 500 images. We’re talking 83 minutes here. And this extra importing time is a deal-breaker if you have a high-speed editing workflow, say you’re a sport, wildlife, or journalist photographer. And this downside alone is worth reconsidering to some photographers.
First Party Compatibility
DNG doesn’t work with most first-party manufacturers’ software. So Nikon’s Capture NX, Fujifilm X RAW Studio, or Sony Imaging Edge won’t read DNG’s. The only way to use these tools is by embedding the RAW file into the DNG upon conversion. But unfortunately, that doubles the file size and removes one of its key advantages. It’s also not guaranteed to work. So if you prefer using the camera manufacturer editing software, you may want to skip DNG altogether.
Some camera-specific metadata is lost during the conversation if it’s not recognized correctly. And, sadly, it’s impossible to recover afterward. This metadata may include the focus point, picture controls, shutter type, GPS data, and copyright information. Adobe claims all metadata is retained during the conversion, but that’s not always the case. So it’s wise to test this for yourself to see if it applies to your specific camera make and model. And it may be best to use RAW files if it does, as they’ll maintain all of your EXIF data.
Long Backups & Risky
Saving a change to a DNG requires creating a new DNG file altogether since they lack the XMP sidecar files that RAW has. So every edit that’s saved needs a whole new file. And this slows down both the speed of backing up files and editing images to a certain extent. It’s mainly a problem if multiple editors work on a single image, as it requires them to have the DNG file to make changes. For RAW, however, you can merely upload the small XMP file, saving well over 30 MB of uploading space and time. So if you’re part of a retouching agency or commercial team, using RAW is best to avoid the hassle of transferring DNGs.
But more importantly, since the changes are recorded into the DNG itself, you increase the chance of file corruption by continually editing it. With every edit, the more likely it’ll eventually become corrupt. And this is quite concerning, as you lose not only the edits but also the entire file itself. Even worse if you embed the RAW file. At least with RAW alone, if the sidecar is corrupted, you still have the original file intact. So the best means to solve this problem is backing up both the converted DNG and the original RAW files separately. Granted, that will remove all of the file-saving benefits in the process.
Conclusion: Should You Use DNG or RAW?
As with many things, the answer isn’t black and white. But, for now, it’s not immediately necessary to convert your photo library to DNG since most cameras on the market have adequate support. But, it may be something to consider long-term if you have concerns about reviewing images from much older cameras.
It’s also something to consider if you’ve experienced a major operating system update recently, say Apple’s M1 architecture, that causes a slew of software to become obsolete at once. Then, that would be an excellent opportunity to convert your existing library, as Adobe will continue delivering updates to this ecosystem. Granted, you will potentially lose some original metadata in the process.
In the end, though, Adobe had great intentions with the DNG format. But, it didn’t quite dominate the photography community as planned. Still, it’s a format I use because we work with so many different cameras and RAW formats. And it’s simply too inconvenient otherwise. But, it’s a shame to see it not become more standardized across all the camera manufacturers. Instead, it’s yet another file format out there and yet another decision to make.
Thankfully, despite not being adopted by the biggest camera manufacturers, it’s not going anywhere anytime soon. So if it works for your workflow, it’s a great option, especially if you only edit with Adobe products. And at least you now have a much better understanding of how it can benefit you.