So one of the advantages of doing this kind of prototyping in Keynote or Powerpoint is that you can use features such as hyperlinks, animations and page transitions to simulate the navigation experience that the user would have in the iPhone app.

Just my the iPhone Photo Album app sample mockup to see what I mean:

When you click on the Photos icon on the home screen (in presentation mode), you’ll see that I’m simulating the loading screen using a timed slide. So it feels like the iPhone is loading the app.

After you click on the “Yeti Sightings” photo album, notice how the transition mimics that of the iPhone. What’s the trick? A “push” slide transition creates the same visual effect as you would get on the iPhone.

If you play with the links in the mock-up, you’ll notice a few other things that help simulate the experience for the user.

Try doing that in Photoshop!

However, there are limitations. After all, I doubt that the developers of Keynote (and even less PowerPoint) knew their software would one day be used to create iPhone app prototypes… For example, you can only define one transition per slide, which is fine when you’re moving sequentially through the presentation. But when there are hyperlinks all over the place, you can’t specify which hyperlink should trigger what type of transition effect. Anyway, I consider these limitations pretty minor considering other prototyping tools don’t even come close to offering transition capabilities.