If you are a digital photography enthusiast, you already know that the best way to preserve most detail in your photos is to shoot in RAW. There are countless photography websites and magazines advocating shooting in RAW vs JPEG, and benefits you get in post-processing. However, which camera raw file format to use ?
What is RAW ?
RAW file is basically a camera sensor dump. All the information that camera sensor records will be stored in the RAW file. When comparing to the film photography it would be equivalent of a film negative. Each camera manufacturer uses their own proprietary camera RAW format (i.e. NEF for Nikon, CR2 for Cannon, PEF for Pentax…). These files are referred as the “true RAW” image.
Benefits of using RAW
- More Information Stored – Despite the fact that DNG is also considered RAW format and stores whole image, there will be always few parameters that are vendor or camera specific, that are stored in the RAW file. In example, focus point, image settings, etc.
- Better Image Quality ? – I have seen people commenting that they cannot recover so many details from DNG as they can from RAW. I cannot give opinion here, as I have not much worked with DNG in terms of blown highlights and shadows. If anyone has a comment, I would really like to hear his/her opinion in the comments section.
- Smaller file size – Now, the feeling I got from different forum discussions is that in some cases DNG files are smaller. In my case when I compare the PEF file my camera generated, versus the DNG that the camera generated, the PEF is approx 10-20% smaller. This could vary, depending if your camera generates compressed DNG or not. However, given the price of memory cards, the difference I would say is marginal. However if you have small memory cards, then 10-20% sounds good (especially when you shoot 1000s of photos).
Shortcomings of RAW
- Compatibility – the biggest problem with the RAW files. When I first bought my Pentax K200D, it was so new that my Photoshop Elements (which I was using at the time), did not support it. Unless you are using the software that your camera vendor provides, this can easily happen to you. Despite frequent patches, it may be a while before your camera’s RAW file format is supported, which can lead to problems in post-processing.
- File management – since RAW files do not allow modifications on the photos to be stored in the file itself, all modifications have to be stored in the sidecar (.XMP) files. That means if you want to move your photo, suddenly you have 2 files to worry about (the RAW and XMP) which is a definitive setback from my view.
What is DNG ?
DNG (Digital Negative) is an open standard format introduced by Adobe. DNG still contains RAW data from the camera sensoj, but is not camera dependent. Camera RAW files can be converted to DNG format, but not vice versa. Some newer cameras support DNG as their RAW format (e.g. Pentax K-7), while others (like Leica and Hasselblad use it as their native RAW format).
Benefits of using DNG format
- Compatibility – DNG is supported in all major photo editing tools and works well with any Adobe tool out of the box. That means that you do not have to worry if your camera is supported by the newest release of Photoshop, Lightroom, or any other editing tool.
- File management – DNG allows for storing data about photo and metadata modifications in the DNG file itself. That means, 1 photo – 1 file. I saw people on the forums stating that in that case the original image is destroyed. That is wrong, as modifications to the photo are recorded in the metadata section, so the original RAW data inside the DNG file is unchanged.
- Recording Speed – Since DNG files are not so much compressed as PEF (at least in my camera), the shooting rate is slightly faster if I use DNG instead of RAW.
With the introduction of Lightroom 4 (which is currently in beta), advocates of DNG will find 3 more benefits, according to CNET’s article by Stephen Shankland:
- “Fast-load data,” a miniature raw preview image embedded in the file that makes it faster to switch among images in Lightroom’s develop module–eight times as fast, according to Tom Hogarty, principal product manager for Lightroom.
- “Tiled” DNG files divided into parts so multicore processors can read and write them faster.
- An option for “lossy” compression to dramatically reduce file size–though because data from the original is lost irretrievably, this option likely will hold appeal only in some scenarios.
Special thanks to Matt Kloskowski, for bringing this article to my attention.
Shortcomings of DNG
- Conversion process is required as some cameras do not support DNG format directly. The conversion process takes some time and slows down post production.
- Compatibility with older versions of software. New versions of the DNG specification can mean older software can’t read newer files.
So, the question of the day is which raw file format to use DNG or RAW. Until today, I have been consistently using RAW format, as I had an impression from my old Pentax K200D (which also had DNG feature), that DNG files are 2x the size of the RAW. Doing research for this article has changed my perspective. I believe I will convert my RAW files to DNG as soon as possible, as I find sidecar files annoying, and given the size difference (10%) between RAW and DNG, I think DNG is the way to go (in my case at least). The announced changes for DNG handling in Lightroom are just icing on a cake, sweetening already sweet deal
Share your comments with us. What is your opinion ? RAW or DNG ?