Not having the new iPad to test, nothing is for sure. But based on how iPhone retina display works...
The iPad will still still have the logical resolution of 1024x768 points. Each point correspond to 4 pixels. So now whatever you specified is based on points - so when you put in a 320x200 pictures, it is possible that iBA is trying to use the 640x400 pictures (just possible, as nobody knows how it works). This is how Safari works in iPhone too - the text is rendered in 4x, pictures are taken in 4x resolutions and display to you.
It is highly possible that anything in photo gallery is automatically in highest resolution.
Tim Cook said, during today's event "If your images look good on an iPad 2, they will look even better on a new iPad." I'm inclined to believe him
You are completely missing the point. A 1024x768 image on the iPad 3 will not look better. A 2048 x 1536 image will. It will be twice as sharp. Your eyes — your 'retina' will not be able to distinguish individual pixels - but only, only, only if the image resolution takes advantage of the screen resolution.
I don't have the new update so not sure how importing the higher res images works, or authoring for the new ipad etc.
But I would guess that you would import an 2048 x 1536 image to fill the screen, will test tonight.
Also what happens to a "Retina" ready ibook when viewed on a ipad 2/1?
Does it save media at 2 resolutions? etc., maybe it does it all on the fly.
I think I have an answer for you.
I placed a 2048 x 1536 image in a IBA document and scaled it to fit the page.
exported as a .ibook in both IBA 1.0 and IBA 1.1
then opened the package and looked at the assets.
In version 1.0 the image was replaced with a 1024 x 768 image (half the pixel size of the original)
in version 1.1 the image remained the original 2048 x 1536.
So in version 1.1 the file size was larger (2.6 m vs 1.8 m)
(the actual jpg was was (123k vs 70k)
it was 930k before bringing it into IBA (not sure what compression quality IBA is using, but seems like medium #5)
So in the New iPad it is pretty clear it will display at the large size. (264dpi)
the version with the 2048 x 1536 image displayed fine on the ipad2, it must downsize it on the fly.
There did seem to be a noticeable delay on displaying that page though.
I will need to test that more.
Hope that helps.
Optimizing performance in your iBooks Author books [ support.apple.com/kb/HT5117 ]
Working with images
- Use JPG for opaque raster images and PNG for transparent raster images whenever possible.
- Resize, crop, and rotate images to the desired size and rotation before importing them into iBooks Author.
- Use an sRGB color profile in your images to improve size and processing time.
- If you need to use high-resolution images in your book, wait to add them until your book is near completion.
I don't think you understand what this discussion is about. I am asking what the guidelines and best practices are for optimizing graphics for display on the iPad 3, not how to optimize the performance of those books. I know they both have the word "Optimize", but the question is very different. I suspect Barnheisel is onto something — most likely that graphics simply need to be doubled (specifically doubled) in size, but not area. Again, the 'Full Resolution" button on the inspector is misleading in this regard as selecting it would lead to images that display at half the available resolution of an iPad 3.