Bridge's raw xmp files

Whenever Adobe Bridge updates a raw file, it stores the data in an external "xmp" (Extensible Metadata Platform) file with same basic file name as the original. If your raw file is called "sunrise.nef", then the corresponding xmp file is "sunrise.xmp".

The idea behind this is excellent. The raw file contains exactly the data that came out of the camera and nothing else, and you can trust that nothing has been changed - by Bridge.

The drawback is of course that you have two files that need to stick together. If you move all files created a certain date from a folder, it is not at all certain that the raw and xmp files are created the same date, so they may get separated.

Nikon's Capture NX instead stores all modifications in the nef file itself. That may be seen as a drawback - a raw file is no longer what came out of the camera. However, there are ways inside Capture NX to remove the modifications, so it is not that much of a drawback.

Aperture has yet another approach. It stores the modification in its own database. When you export the Master you get the choice whether you want to include the IPTC data or not. The IPTC is the only data Aperture allows to change in a raw file. The rest of the image is intact, as it came out of the camera. Other changes need to be exported through other file formats, like tiff or jpeg.