I don’t do much lengthy writing on this blog, I try to keep it to just photos and captions, but this issue has been on my mind lately and I feel it is important enough to warrant a blog post.
Over the past few days I have been rethinking how I manage my digital workflow with regards to RAW photo files. Most digital photographers understand the importance of shooting in RAW (i.e., Canon CR2, Nikon NEF), so I won’t discuss RAW vs. JPEG here, but if you aren’t shooting in RAW just know that you should be.
The question I have been debating is “To DNG or Not to DNG”, and I think there are strong arguments for both sides.
First, it is important to know that I am an Adobe Lightroom user. This has a particular influence in my decision making because Lightroom manages and handles RAW and DNG files differently than other cataloging programs (i.e. Apple Aperture, Expression Media, etc). Most notably, Lightroom keeps track of all metadata (IPTC and RAW Conversion “develop” settings) within its database. It also has the ability to save this metadata back to the original file. In the case of a RAW file, it writes the metadata to an XMP sidecar file. In the case of a DNG file, it writes the metadata to the file itself. I think it is a good idea to save the metadata to the original file, just in case the Lightroom catalog self-destructs or in the case of moving an original file or sending an original file to someone. This will be discussed in a bit, but first I am going to discuss what I believe are the two major issues of RAW vs. DNG:
First, DNG files are “future-proof”. Now nothing is truly future-proof, but the DNG file format seems to be more future proof than the numerous proprietary RAW file formats from numerous camera manufacturers. In my opinion there is a greater chance that 40 years from now Canon will stop supporting the CR2 file format from a circa 2000 camera than Adobe abandoning the DNG format. (Side note, a few weeks back I found a box of Kodak stereo transparencies from the 60’s in my grandmother’s basement, and there isn’t much I can do with them, as Kodak abandoned the stereo transparency a long time ago and I would be hard pressed to find a stereo viewer. So if you think this issue isn’t real, think again.)
Second, RAW files are big, especially if you are shooting with a camera like the Canon 5DmII; you’re talking about a 25mb CR2 file. Converting to DNG cuts down on the file size, unless you embed the original RAW file in the DNG, in which case the DNG file will be larger than the RAW file. This helps save disk space, which is important if you are a photographer on a budget and don’t have money galore for hard drives. However, converting to DNG takes time and also discards some proprietary camera information such as focus point selection, etc.
In light of the two points above, it would seem that DNG would the clear winner. However, I am caught up on one issue: writing metadata to a DNG file. I am a purist and believe that the original file should never be touched. This is for two reasons: 1) the original file should be preserved as is, straight out of the camera, forever; it is your digital negative, and 2) I am a compulsive worrier about file corruption and data loss. Writing metadata directly to the DNG file scares me; what if something goes wrong and the file becomes corrupt forever? XMP sidecar files solve these two issues. With RAW files, the metadata is written to the XMP sidecar file, never touching the original RAW file, preserving it and preventing corruption. Additionally, if you are like me and backup your photos to a second hard drive, it is a lot faster to backup an updated XMP file (20 KB) vs. an updated DNG file (10+ MB). One major caveat to XMP sidecar files: if the sidecar file ever gets separated from the RAW file, all of the RAW file’s metadata is lost.
So… To DNG, or not to DNG, that is the question.