Comment 1 for bug 579804

To be a bit more precise, existing photo collections' tags (i.e. keywords) are normally stored in IPTC and/or XMP data (EXIF can't really hold keyword data). The trunk build of Shotwell can now read IPTC/XMP keywords from photo files; these become Shotwell tags after an import. So this feature will be present in 0.6.

It's true that we have a ticket (#1290) for storing Shotwell tags in photo files. We're currently debating, however, whether Shotwell will do this on the fly or only when the user exports photos explicitly. We're currently leaning toward writing tags out only during an export operation, because if we always store tags in photo files then tagging becomes a relatively expensive operation. A user might quite reasonably want to apply a tag to 100 photos, but if we need to write that tag to 100 10 Mb photo files then now we need to write 1 Gb of disk data in order to apply the tag (since we may need to rewrite an entire photo file in order to insert a new tag into it).

Some other photo programs (e.g. Picasa) do, however, write tags out on the fly; others (e.g. iPhoto, Aperture) do not. F-Spot gives the user the option whether to do this.