Digital Publishing for tablet devices like Apple’s iPad or Motorola’s XOOM reverses format choices: instead of choosing a paper format freely for a print magazine, the page size of digital publications is defined by the device displaying it. This is important when automatic scaling / re-layout is not an option (that is the case for nearly all digital magazines, however there are solutions for it in the future).
The iPad (1&2) comes with a 4:3-Screen resolution of 1024x768. That looks old-fashioned and bad for all the 16:9-Video, but comes in quite comfortable for porting print formats to the screen.
Difference between iPad and DIN A4 sheet: 7 %. (compared to 33 % unused space when letterboxing DIN A4 to 16:9-Screen of XOOM)
Current solutions need you do re-layout your publication for each device dimensions (Adobe is calling these “renditions”).
Another important thing about device dimensions is handling. 7” Tablets (like the Samsung Galaxy Tab, HTC Flyer or Blackberry Playbook) are designed to be held in one hand. 10” Tablets (like iPad or XOOM) are designed to be layed down or held by both hands. But they all need to fit in bags and cases, because they are unfoldable like newspapers, of course.
You will not be able to sit in a coffee shop and read a digital magazine like you did a classic newspaper: read it while hiding like an agent in old spy movies.
Here is a comparison between 1 human hand (timeless), 5 tablet devices from 2011, 3 magazines (from US) and 5 newspapers (1 US, 4 German).
This comparison shows that all tablets are actually smaller than printed magazines and much smaller than newspapers (half opened, not folded as they are sold).
When adapting content or ads from print, it is important to match one aspect ratio closely to only marginally loose content. In this case, the 4:3-screens are in advantage of the 16:9-resolutions.
Another reason why these tablets appeal to us immersivly, is the size: A size Frank Chimero calls “Human Sized” (here as an format for a traditional book, “The Shape of Design”).
In this chart all compared devices and print publications are put together in absolute size comparison (top) and in normalized aspect ratio (bottom).
If you need a clear version of these, here is a PDF containing both charts.
If you need to adopt content for different screen aspect ratios, maybe this toolset for managing screen solutions from punchcut is a helper.