Today’s Question: I’m looking at a couple of camera systems that offer varied advantages for my intended use. Suggestions regarding RAW conversion with one system are mixed. The other system offers DNG capture files. I’m curious if DNG has a decided advantage over other proprietary capture files when brought into Lightroom?
Tim’s Quick Answer: In my view the issue of using DNG files is a bit mixed, but on balance I prefer not to use the DNG format. This is primarily related to other workflow issues, however, and doesn’t relate to any image quality issues or other significant concerns.
More Detail: The Adobe Digital Negative (DNG) format was introduced as an openly documented alternative to proprietary RAW capture formats. While I certainly understand the concerns about proprietary RAW file formats, the availability of many software tools for processing these proprietary RAW formats makes those concerns largely unfounded in my view.
Therefore, I prefer to focus on the workflow considerations as they relate to the DNG format compared to RAW capture formats. That said, I would certainly concede that there is at least some advantage to using a format that is openly documented, compared to proprietary RAW formats that need to be reverse-engineered in many cases in order to be supported by image-processing software.
The DNG file format is capable of applying lossless compression to the image data, which helps to produce smaller file sizes than proprietary RAW capture formats without sacrificing any of the image data. In general a DNG file will be somewhere around 20% smaller than a similar proprietary RAW capture format. This can obviously be a considerable advantage when it comes to storage requirements.
One of the features of the DNG file format that is often touted as an advantage is actually something I consider to be a significant disadvantage for my workflow. That feature is the ability to embed metadata updates within the DNG file rather than storing that information in a separate XMP “sidecar” file as is the case for proprietary RAW capture formats.
One of the key problems with storing metadata within the DNG file is that doing so complicates the process of backing up that metadata. If you are using a synchronization-based approach to backing up your photos, for example, then updating metadata for a photo typically requires you to backup a completely new copy of the DNG image rather than simply updating the very small XMP sidecar file.
I would certainly say that there is no problem with using the DNG file format as a capture format in your photography as it relates to overall image quality. However, I do feel there are some disadvantages from a workflow perspective that cause me to prefer the use of proprietary RAW capture formats rather than DNG.
That said, I’m not sure this issue is important enough that I would choose one camera over the other based on whether a DNG versus proprietary RAW capture format were available with the camera.