The image size: 1600x900 Smartphone Format

This featured image to the right is in a 1600x900 Smartphone Format

You can see what gets displayed by comparing the image below with the featured image.
According to what you discover you should take your images with your camera. The visible part will be always focussed on the center of the image.
As you can see you need to keep the Object Focus right in the middle area when taking portrait shots with a Smart Phone. The longer the screen the more the visible area will be reduced. in height from the center of the image