Here are a few tips for decide how to go about merging your libraries
- If you have more than two libraries to merge together, you can either merge one library at a time, or you can do the entire merge in one operation by checking multiple libraries on the left hand side of the merge setup sheet. Merging one library at a time gives you more control, allows you to split up the process, and verify that the merge is getting the result that you expected. Merging everything at once, however, is handy if you need to run the process overnight or when you are away from the computer, without having to attend to it.
- Merging into a new library will ensure that your source libraries remain intact, in case something interferes with the merge process, or you decide you want to revert to what you had before merging. The disadvantage to this is that all the photos from all the libraries being merged will have to be copied, so the merge will take longer than if you were to choose all but one of the libraries as the sources and the final library as the destination.
- One way to get the best of both worlds is to use the "Duplicate Library" command on one of the libraries before merging (preferably the largest one), and then merge the rest of the libraries into the duplicate library. Duplicating a library is faster than merging, since it's just a straight copy of the folder, rather than having to reimport all the photos into a new library. Another benefit of this method is that you will be able to preserve items that aren't copied during the merge process (such as folders, books, and slideshows) in the library you duplicate.
- If you need to continue a merge that was interrupted midway through, the "Don't import duplicates" and "Combine albums with the same name" options in the "Photo Copying" tab in the preferences can come in useful. The duplicates pref will cause the merge to skip over the photos in all the rolls that were already imported and only start importing once it reaches photos it didn't get to the first time. Note that iPhoto 6 has some bugs when it comes to identifying duplicates correctly, so duplicates may be imported even if this option is checked on. Having the "combine albums" pref enabled will then cause the imported photos to be added to the albums that were created during the first time through the merge, rather than creating an entire new set of albums.
- You can use the merge command as a way of verifying the photos in your library and identifying corrupt ones. Start a merge, choosing just the one library you'd like to verify as the source library, and create a new library as the destination. As iPhoto Library Manager goes through importing all the photos, if there are any that have been corrupted, they will be identified by iPhoto as such when it tries to import them. You can then use that information to remove or replace the corrupted photos in your library.
- Some users can experience problem after having upgrade a library through one or more upgrades to iPhoto, as sometimes information can be corrupted during the upgrade process. You can perform the same type of merge as above, but keep the resulting library after it's done. Since the newly created library never touched any previous version of iPhoto, it will not have any of the legacy data lurking around from previous version. Do remember, though, that folders, books, and slideshows won't be preserved by a merge, so if you have these items in your library that you want to keep around, you'll probably want to eschew this method of library "cleaning".
- If the libraries you're merging have lots of duplicates that you don't want to have imported more than once, you'll probably want to check both the "Don't import duplicates" option as well as the "When recreating albums, use existing photo in place of duplicates" option in the preferences window. This will ensure that any photo identified by iPhoto as a duplicate will only be imported once, and that copy of the photo will be added to any albums in the merged library. Whichever copy of a particular photos gets imported into the merged library first will be the one that gets used, so if you prefer to use photos from a particular library, either use that as the destination of the merge or make sure it gets imported before any other libraries that have duplicate copies of photos.