Tablet publishing on the new iPad White Paper

Question

http://blogs.adobe.com/digitalpublishing/files/2012/03/DPS_iPad3_bestpractice.pdf
I was reading through this article and most of it makes is pretty clear.
Can someone go into further detail on Overlays (resampled and pass-through) - specially in regard to resolution of assets (72 and 144)???
What is the best resolution to use for different asset types and for different iPads?

Answer 1

It would help if you provide a more detailed question. I'm afraid a rambling answer might might this seem more complicated than it is, but here's my take.
If you create a 1024x768 folio (no renditions), you don't need to concern yourself with resolution of assets. Use 72 ppi images as always.
If you create separate 1024x768 and 2048x1536 source files with two renditions, use 72-ppi images.
Let's suppose you're using one set of source files -- 1024x768 -- to create two renditions. When you import the articles into the 2048x1536 folio, the background content and overlay view areas are scaled up. What happens you have a slideshow, an image sequence, a video, and an image pan on a page?
Slideshow -- The slideshow is not a pass-through overlay, so the content on each state is scaled up and resampled as a PNG file. (If you're using the PDF image format, text and shapes in a slideshow are rasterized, unlike text and shapes that aren't part of an overlay.) In other words, you don't need to make any changes to slideshows or other resampled overlays (buttons, audio skins, scrollable frames).
Image Sequence - An image sequence is a pass-through overlay. That means if you created 400x300 72-ppi jpg images, these images are not scaled or resampled on upload -- they're simply passed through. For the hi-res folio, this is the equivalent of scaling up 400x300 images in an 800x600 frame. But with the retina display, image sequences look good on the iPad 3, though not as clear as if you use 800x600 72 ppi images. As I see it, you have three options: (1) just use the 400x300 image sequence, (2) create 800x600 source images and scale them down to a 400x300 view area, which looks great on both devices but increases folio size, and (3) create two sets of assets and put them on two different layers (or create separate 2048x1536 source documents).
Video -- Videos are pass-through overlays. Like the image sequence, a 400x300 inline video appears in the equivalent of an 800x600 area on the iPad 3. The same options apply.
Image Pan - This is the tricky one. Suppose you have an 1200x1200 72-ppi image in a 400x400 view area. On the iPad 1, you pan the 1200x1200 image within the view area. On the iPad 3, you pan the 1200x1200 image within the equivalent of an 800x800 view area -- the image pan overlay is restricted. For Pan & Zoom images, the best approach is to use different images. In this example, you would use the 1200x1200 image for the iPad 1 and a 2400x2400 image of the iPad 3.