to remove duplicate images from IPhoto and Aperture.
There is no straightforward way in the program itself to do this...
but you CAN (my Apple genius told me).... get an app for that!
Try the Duplicate Cleaner for Iphoto for Mac (here) .
Before installing this FREE app, I read the reviews, and was prepared (as is usually the case when I try to fly techno-solo on my mac) to be frustrated, exasperated, and extremely irritated.
But surprisingly, NOT SO! It worked like a dream, removed over 1000 duplicates from my library, and freed up all sorts of space. Just remember to:
Close all other applications and windows
Temporarily turn off photo stream
Try it more than once, if the first attempt is unsuccessful.
If it solves the problem for you...
my job is done. :)