When exporting JPEG photos with manually entered metadata (like GPS, keywords, faces), and trying to retain the original pixel-for-pixel JPEG, the best iPhoto can do is export the photo as a JPEG with Maximum quality and the checkboxes selected to include the title and location info. However this option will take a 2MB file and turn it into a 4MB output, for example. This makes me believe iPhoto is taking the original JPEG and instead of just embedding on the EXIF metadata, it is actually re-compressing the JPEG and somehow doubling the size!
Searching internet threads for a solution makes me realize most iPhoto users don't understand that exporting a JPEG file at the maximum quality should just return the JPEG used as the input, and tacking on metadata does not require re-compression. Since JPEG is only a lossy compression format, it doesn't even make sense that file size would ever increase.
For comparison, Aperture handles this correctly. You can get an original file back with the metadata tacked on without going through re-compression and file size doubling. So it seems some employees in Apple know how this should work but for some reason this bug has never occurred to anybody on the iPhoto team.
Keep this in mind if you ever decide to move your photos to a program other than iPhoto, or share trip photos with somebody where you've entered the GPS data. Exporting your library is going to mess up your originals.
Searching internet threads for a solution makes me realize most iPhoto users don't understand that exporting a JPEG file at the maximum quality should just return the JPEG used as the input, and tacking on metadata does not require re-compression. Since JPEG is only a lossy compression format, it doesn't even make sense that file size would ever increase.
For comparison, Aperture handles this correctly. You can get an original file back with the metadata tacked on without going through re-compression and file size doubling. So it seems some employees in Apple know how this should work but for some reason this bug has never occurred to anybody on the iPhoto team.
Keep this in mind if you ever decide to move your photos to a program other than iPhoto, or share trip photos with somebody where you've entered the GPS data. Exporting your library is going to mess up your originals.