Comment 5 for bug 579804

Another factor to consider here: starting with Shotwell 0.6 the user can import RAW photos from cameras. The exiv2 library can't write metadata into most RAW formats (run "man exiv2" to see a list of formats and the metadata which can be read/written into them). Writing metadata into a RAW file is considered slightly risky even when using programs such as Aperture; see http://aperture.maccreate.com/2010/02/10/write-iptc-metadata-to-masters/ for a discussion, for example.

So if a photo is RAW, we can't realistically keep up-to-date metadata in the photo file; we can only store it in the Shotwell database and/or a parallel JPEG file generated from the RAW photo.

Perhaps someday camera manufacturers will converge on a single RAW format where software can easily update metadata; DNG is the best hope for that. That day is probably far off, though.