iPhoto managed or referenced library

[Mythbusters]

I unchecked the box "Copy items to the iPhoto library", because I don't want iPhoto to duplicate my photos, but it still copies them. What could be the problem? I want to use my organized photo library as a referenced library in iPhoto.

 

[Weaselboy]

What makes you think it still copied them? It will make "previews" for those images and that may be what you are seeing.

 

[Dave Braine]

I would go for the "Copy items to the iPhoto library" option as this will prevent problems in the future when you have unwittingly/mistakenly deleted the originals, or you don't have the external device that they were on to hand.