1 DNG is a 101 page overambitious spec that tries to be an interchange format for processed images, complete with image transformation operations. We just implement enough of the spec so that actual raw files from DNG producing cameras or the Adobe DNG converter can be read. 2 Files that are just the raw data itself with no metadata whatsoever. The most common of these are the files generated by the Canon CHDK hacked firmware. Later versions produced actual DNG files but the first ones just did a dump of the raw data next to the JPG and assumed the user would use the JPG for the metadata. We match them by the filesize itself which means that if you feed rawloader with a file that has the exact same bytecount as these files you'll get a nice garbage output...