Dan Saffer illustrates how different parts of the screen are easier to reach on mobile touchscreen devices. The next step would be to show how activity zones change as the device is held differently (shooting photos or videos, holding the smartphones single-handed vs two-handed, when the device is held in a mount). But it’s a very useful exercise to illustrate where the action is easiest before starting to sketch screens.
“Looking at some apps for both iPhone and iPad, I discovered some of the best of them have placed controls in ways that best match the ergonomics of our hands while holding them, particularly the saddle joint of the human thumb, with its ability to roll in a particular almost-45 degree sweep. In order to access other parts of the screen requires a reach with the index finger or an extension of the thumb to access it.”
Link: Activity zones for touchscreen tablets and phones (kickerstudio.com)