From email:

I have used DupeGuru PE in the past and find it to very useful for searching for duplicates or similar pictures in a folder. However, it is harder to use on iPhoto or Aperture libraries when these conain many (thousands) of images. My way of doing this (using iPhoto as an example) is first to group images for which I think there might be similarities into either an album or a smart album, export them to a folder, apply DupeGuru PE to the folder and then reimport them into iPhoto.

It would be much more convenient if there were way to apply DupeGuru PE only to a choosable album and/or smart album in iPhoto rather than to the entire iPhoto database. This would be big help and time saving since it would eliminate the export/import steps.