Tip: Image resolution in slide shows
When you have created a slideshow, you can opt to allow full screen zooming via double tap on the iPad. To do this, you need to select "Export full screen slide shows" when exporting.
This means however that, for optimal results, your images should have a 132 ppi resolution at 1004 x 768 pixels in landscape and at 748 x 1024 pixels in portrait.