Using Aperture libraries with iPhoto 9.3 and later

Starting with iPhoto 9.3 and Aperture 3.3, Apple has added the ability for Aperture and iPhoto to directly open each other's libraries, without having to import photos back and forth between them. iPhoto Library Manager does support working with Aperture libraries if you have iPhoto 9.3 installed on your machine, though all operations on such libraries will still be performed via iPhoto. Aperture library names end with an extension of “.aplibrary”, whereas iPhoto libraries either have an extension of “.photolibrary”, or no extension at all.

• You can add Aperture libraries to iPhoto Library Manager alongside your iPhoto libraries, either by using the "Add Library" button or by dragging an Aperture library into your library list.
• You can open Aperture libraries in iPhoto just like iPhoto libraries, by double clicking the library you want to open in your library list.
• iPhoto Library Manager does not provide any method for opening libraries directly in Aperture. For that, you will need to open Aperture and tell it what library you want to open.
• Note that any given library can't be open in both iPhoto and Aperture at once. If you try to do so, the second of the two applications that you try to open will display an error message.