So, you’re wondering if you should convert your RAW files to DNG. If you want the short answer, I made a pros and cons table above. However, if you want to dive a little more deeply, continue reading.
What Is a RAW File?
RAW files are one of the file formats that you can shoot in with your digital camera. Each camera brand uses its proprietary information to generate its RAW files. Meaning, each camera brand uses its unique file extension for RAW files. For example, Nikon uses NEF, Canon uses Cr2, Sony uses ARW, and Panasonic uses RAW.
When you edit RAW files in post-processing, you can either use your camera manufacturers’ or a third party editing software that supports your file. RAW files are unique in that all metadata* created during the editing process is saved in a separate text file. This file is known as a sidecar file. A sidecar file stores all changes made to your original image separately leaving the original RAW image untouched.
*Image metadata is defined as camera-specific information such as the camera settings that accompany an image. Post Processing metadata is the information regarding all the changes you made to your photo during post-processing.
What Is a DNG File?
DNG stands for “Digital Negatives,” Adobe created the DNG to establish a universal file format used by all cameras and software. To promote this industry standard file format, Adobe published the DNG’s proprietary information to in order to facilitate the widespread use of the DNG file.
One major distinction between DNG and RAW files is that all metadata is stored within the DNG file. Meaning, DNG files store camera-specific metadata, JPEG previews, and post-processing changes within itself.
Unlike Raw files, most cameras don’t shoot in DNG. You must convert RAW files into a DNG with a computer after they have already been taken. However, the conversion process often results in smaller file sizes for the same photo.
Reasons to use DNG Files
1. Longevity
There are two concerns that photographers have about the longevity of RAW files. The first is the fear that support for much older RAW files will be discontinued, leaving them unreadable. The second is the fear that if a camera company goes out of business support for their file formats will be discontinued. Kodak for example, terminated support for their RAW files several years after going out of business. Adobe’s solution was to create the DNG file format and release all its proprietary information. By doing so, any software company can easily establish support for DNG files with ease long into the future. The longevity of DNG gives photographers peace of mind knowing their files will be readable regardless of the age of their files or which camera or software companies are in business.
2. Storage Space
The compression algorithm used during the conversion from RAW to DNG reduces file size while maintaining the same image quality. The amount of storage space saved when converting to DNG will depend on the photo and the camera used. In my experience, DNG’s are on average 15% smaller than the original RAW files. While the file size differences may seem minor, when applied to large volumes of files it can result in significant storage space reduction.
3. Checksum Validation
DNG files are also very useful because they have a built-in validation feature. This validation feature allows you to check whether your files have been corrupted. The feature can be applied to entire libraries, allowing you to spot corrupted files easily.
I recommend using it whenever you transfer files from one storage source to another. This will make spotting corrupted files during the transfer easier. However, one downside of this feature is that it can’t prevent a file from being corrupted; it simply notifies you when a file becomes corrupted.
4. Self Contained
Using DNG allows you to efficiently store all the information for one photo in a single file. While RAW files save metadata in a separate XMP text file, DNG files are capable of saving all metadata within itself. This means, DNG files only require one file for each photo whereas RAW files require two.
DNG files also give you the option of saving the original RAW file inside the DNG file. The RAW file embedded within the DNG can be extracted at any time. This means that even if you convert to a DNG, you will never lose your original raw file. However, doing this will significantly increase the size of the DNG file eliminating any space-saving benefits DNGs typically offer.
If you plan to embed the original RAW file within your DNG, I recommend simply keeping a copy of the RAW file stored separately. This ensures that in the event that your DNG file becomes corrupted you don’t lose your RAW file as well. Using this method allows you to back-up your files while using virtually the same amount of storage if the RAW file was embedded.
Reasons to Avoid Using DNG Files
1. Lack of Format Compatibility
Adobe has had little success in converting DNG’s into the standard file format used when dealing with raw data. Although, Adobe claims that the future is bright for DNG and it will become the standard file format in the future, current trends don’t support their claim. Over the last several years only a handful of camera manufacturers have incorporated DNG as a shooting setting in their cameras. Many of the largest camera manufacturers such as Nikon, Canon, Sony, Panasonic, and many others do not support DNG as a shooting setting in their cameras or as a valid file format in their processing software.o
2. Irreversibility
Only a handful of cameras possess the ability to shoot directly in DNG. If you are not using one of the few who can, you will need to use a DNG converter. The conversion process destroys the original RAW file and replaces it with a DNG file.
While DNG converters offer the option of embedding the original RAW file within the DNG file, doing so will make the DNG files larger. Unfortunately, if you don’t embed the file there is no way to convert back to a RAW file. The alternative is to save a copy of the RAW file as a backup. But again, any storage space efficiencies are moot at this point.
One additional downside of converting to a DNG file is that some of the original metadata that is contained in the RAW file may be lost. Adobe claims that all metadata is transferred during the conversion but many accounts point otherwise. To determine if the metadata lost during the transfer is important to your photography workflow run a test. Create a copy of a RAW file, convert it to DNG, and then compare the metadata within each one.
If the metadata lost in not important to your workflow there is not important to you then there is nothing to worry about. On the other hand, if the metadata lost is essential to your workflow it might be best to use RAW files.
3. Conversion
The time required to convert a DNG file to a RAW file can be time-consuming when dealing with large amounts of photos. It typically takes anywhere from 2-5 seconds to convert a RAW file to a DNG. This can be higher for larger file sizes.
While the time required seems minimal, this can be exacerbated if you have many files. Let’s say it takes on average 5 seconds to convert a single RAW file to a DNG file. If you have one thousand photos it would take nearly one and a half hours to convert your photos.
4. Processing Issues
When you edit a DNG file you increase the chances of file corruption. Unlike RAW files, DNG files do not have sidecar files. This being the case, any edits made in a DNG file is made directly within itself.
Eliminating sidecar files increases the chances of corruption because the more you open a file and edit a file the more likely it is that it will become corrupted. This is especially concerning because if the DNG becomes corrupted, not only do you lose the changes, but you lose the entire file itself. With a RAW file, if your sidecar file becomes corrupted your RAW file remains intact.
In addition, saving changes directly to the DNG file increases the amount of time required to save your file. While editing RAW files require a much smaller text file (XMP) to be saved when changes are made, DNG requires its entire file to be saved again. That is since DNG save metadata directly within itself the entire file needs to be backed up again. This decreases the efficiency of your workflow along with the time spent backing up your data.
Lastly, when processing with a DNG file you are restricted to the software you can use, primarily due to the fact that most camera manufacturers software does not support DNG. In addition, software outside of Adobe products may incorrectly display DNG files. Ofen the display contains inaccurate colors and longer rendering times. To be certain test your DNG files before you commit to using one post-processing software.
5. Future Compatibility
Though some people are afraid that third-party processing software may discontinue support for old their old RAW files, I don’t worry about this issue. It is unlikely that software companies terminate support for older raw files since continuing to support older file format does not require additional effort.
Most software simply adds additional support during updates rather than remove their support for older files. Even if third-party support is removed for older RAW files, most camera specific processing software will support every version of their file formats. For example, Nikon does not discontinue support for older Nikon RAW file formats on their Nikon Capture NX-D software. To be safe, always have your manufacturer processing software as a backup.
Should You Shoot in RAW or DNG?
As a landscape photographer, DNG does not have enough advantages to motivate me to switch from RAW and here’s why:
1. Longevity
While the hope is that DNG’s are the file of the future, the trend shows otherwise. The top camera manufacturers and many others still do not offer a shooting setting for DNG (If this becomes an option on most cameras, I may reconsider).
The concern that third-party support for older RAW files may be discontinued is unreasonable for two reasons: First, software companies rarely remove support from their software. Second, the availability of camera manufacturer software eliminates any concern of possible discontinued support from third-party software.
2. Storage Space
While DNG files offer storage space efficiencies, its benefits are minimal. For example, the price of storage space in terms of SD cards and hard drives has decreased drastically over the years. You can purchase a 4TB hard drive for around $100, and you could double the size of your storage by buying an 8TB hard drive for less than $150.
Let’s say a RAW file is 80MB and that DNG files are 15% smaller in size. That would leave you with a 68MB DNG file.
That translates to . . .
58,800 DNG files inside a 4TB hard drive at $0.0017 per photo.
or
50,000 RAW files inside a 4TB hard drive at $0.002 per photo
At $0.0002 per photo, you can store an additional 8,800 and saving approximately $1.76 by going converting from RAW to DNG.
3. Validation
Though the checksum validation features can notify you about corrupted files, it does not prevent them from being corrupted. In addition, I also prefer to avoid increasing the risk of corruption by continuously editing and saving DNG files. For these reasons, while the validation feature is nice, it isn’t enough to convince me to convert DNG files.
4. Self Contained
The fact that RAW files use one additional file to store metadata has never truly affected me. Having an additional XMP file doesn’t affect my workflow because processing software can automatically locate images corresponding XMP file.
I can also address the issue of having multiple files by storing them in an organized fashion. Doing so makes XMP files virtually unnoticeable.
Summary
If you are wondering if you should convert your RAW files to DNG, know that there is no correct answer to this question. You will have to make a decision based on your photography workflow needs and preferences.
Personally, the benefits of DNG are not enough to make me convert my files. Though DNGs offer some great advantages the disadvantages of the formats compatibility, conversion time, and increased risk of corruption are enough for me to stay with RAW format.
