Your Eventful Life
iPhoto 8 does away with the "film roll" metaphor that earlier versions used. That makes sense, given that iPhoto is probably being used by more and more people who have never touched a roll of film.
In iPhoto 8, each set of photos you import is stored as an <em>event</em>. You can split an event into multiple events if you like. For example, if you have an event containing shots from a morning hike and a sunset campfire, you can split the event into two separate events to more accurately reflect your day.
To split an event, double-click it to display its thumbnails. Then, select the photos from the campfire, for example, and click the Split button at the bottom of the iPhoto window. You don’t even have to select all the photos from the campfire. Just select the first one, and then click Split. iPhoto is smart enough to figure out that you want the subsequent photos in a new event.
You can also combine two events into one: just drag one event to the other. Or select the events, then click the Merge button.
When you import photos, you can have iPhoto automatically split them into events based on a variety of time intervals. Choose iPhoto > Preferences, then click the Events button and explore the options.