Metadata Lost with DNG Conversion


Today’s Question: Am I loosing anything by converting files from Canon raw format to Adobe DNG? I’ve read that it is better to use the camera manufacturer’s raw format rather than DNG because the camera manufacturer may include data that DNG doesn’t include or support. Yet, I’ve never seen anyone name any such data. Do you know of any examples of data that are in native raw files that are excluded from a derived DNG file?

Tim’s Quick Answer: If you convert raw captures to Adobe DNG files and discard the original captures, the only potential information that could be lost would be “private” metadata. This is generally information that requires software from the camera manufacturer to access, with one example being the automatic sensor dust spot cleanup feature available on some models of Canon cameras.

More Detail: When you convert an image from a proprietary raw capture format to an Adobe DNG file you are retaining the original capture data as well as the standard metadata recorded at the time of capture. That metadata would include things like the details about the camera and lens used, the exposure settings, and more.

In addition to the standard metadata fields that are recorded by the camera, there may be some “private” metadata that is created by the camera but not necessarily openly documented. This type of metadata is often referred to as “maker notes” because they are a form of notes recorded by camera for purposes of the company that made the camera.

As noted above, one example of information saved in maker notes supported by some Canon cameras relates to the feature for automatic dust spot removal. When this feature is enabled, the camera determines where there are dust spots or other blemishes on the image sensor, and what amounts to a map of where those spots are is recorded into the maker notes for the capture. That metadata is not available to third party software, which means you need to use Canon’s software to make use of the data to perform an automatic image cleanup.

If you’re not making use of any features that can only be accessed using software from your camera manufacturer, and you don’t anticipate needing to make use of such a feature later, then it is safe to convert your raw captures to Adobe DNG files.