Using Photo Stream with multiple libraries

Starting in iPhoto 9.2, Apple introduced a new feature called Photo Stream, which lets you automatically transfer photos via their iCloud service between your iPhoto library and your other devices such as an iPhone, iPad, or another Mac. This feature works when you have multiple iPhoto libraries set up, but there are a couple things to be aware of.

First, iPhoto will only allow Photo Stream to be active in one iPhoto library at any given time. If you've already enabled Photo Stream in one library, but then open a second library and enable Photo Stream there, this will cause Photo Stream to be turned off in the first library.

Any photos downloaded by Photo Stream are actually stored in an entirely separate location from any of your iPhoto libraries. This means that, even if you do switch Photo Stream from one library to another, you will not need to go through redownloading all the photos you already have in Photo Stream back from the iCloud servers. So, switching Photo Stream from one library to another is a relatively inexpensive operation, so you can do it as often as needed without it being much of a hassle.