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Avoiding importing duplicate photos


Whenever you import photos into an iPhoto library, iPhoto will try to determine if some or all of the photos you're importing are already present in the library. If it thinks that a duplicate is being imported, it will put up a dialog box asking whether or not you really want to import the photo, showing you small versions of the photo in question and the photo it thinks it is a duplicate of. The dialog also has an "Apply to all" checkbox that will apply your answer to any other duplicates detected in the batch of photos being improted.


When using iPhoto Library Manager to copy large numbers of photos, this duplicate detection can interrupt the copying process. There is no way to turn it off completely, and the "Apply to all" checkbox only applies to a single roll/event. Since in many cases (especially when merging libraires) iPLM will be copying many rolls/events at once, if your two libraries have lots of duplicate photos among them, this means having to babysit your machine and answer "no" once each time a new roll/event begins to be imported and iPhoto nags you about duplicates.


To avoid this, you can go to the Photo Copying section of iPhoto Library Manager's preferences window and check the "Don't import duplicates" checkbox. This will query iPhoto before doing the actual import and identify any duplicates ahead of time. If duplicates are found, iPLM will simply skip over them and not attempt to import them into the destination library. This prevents iPhoto from interrupting the photo copying process, since no photos that are duplicates will ever be sent to iPhoto in the first place.


There is another option in the preferences labelled "When recreating albums, add existing photo in place of duplicate". This is enabled by default, and will make sure any albums you copy still have the same number of photos when they are recreated in the destination library by adding the duplicate copy that already exists in that library in place of the photo that is not being imported because it is a duplicate. For example, let's say you are copying an album with 4 photos, and a copy of one of those photos already exists in the destination library.



iPhoto's duplicate detection algorithm works mostly on a combination of filename and the photo's date. It's not 100% perfect, so it is still possible for duplicates to sneak through from time to time.


In the Advanced section of iPhoto's preferences window, there is a checkbox that tells iPhoto to add a ColorSync profile to any newly imported photos that don't already have one. The purpose of this is to help keep colors consistent on different devices, essentially trying to make sure that the color you see on your camera, on your computer screen, and on a printed version of a photo are all as close as possible. There is one downside to this, though, in that adding the ColorSync profile to a photo adds a small chunk of data to the photo file, making it slightly larger, and thus no longer an exact copy of the photo that was imported. This difference can in turn cause iPhoto to miss detecting the photo as a duplicate if it gets imported a second time.


If color matching is important in your photo work, then you'll probably want to keep this option enabled, but if it's not as important to you and you're having problems with unwanted duplicates in iPhoto, you might try turning this option off. Note that if you have previously imported photos that have already had the profile added, it may not help detecting duplicates of those photos, but it may help with any new photos you import into iPhoto in the future.


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