If you have been using Aperture for a long period you will now how easy it is to accidentally import images more than once, especially when bringing in badly-organised older images.

Other Tasks>Find Duplicate Masters... will look through the entire Aperture database attempting to find duplicate Masters.*

There are two options when running the search:

• Test Run will look through the database for dupes, and then show you a list of Version Names.
• Run will do the same and then make a new custom tag called ApAssist Duplicate and place the checksum or filesize in it for all the Versions found. You can then do a search of the entire Library for all images tagged in this way and decide which of the dupes you want to remove.

After using Aperture Assistant to tag the Versions, you will need to search at the top level of the Library for all images with something in the 'ApAssist Duplicate' tag.

*In Aperture 1.5.6 it will look for the checksum that Aperture stores for each Master. In Aperture 2.0 and above the original file size is used instead, occasionally leading to false positives.