In order to maintain proper proportions, a picture will stop to enlarge under the following two conditions:
1. When the picture put horizontally is proportionally enlarged till its width fills with the screen width.
2. When the picture put vertically is proportionally enlarged till its height fills the screen height.
Note: A portion of the picture will go beyond the screen.
If the resolution of the photo is lower than 800x600 in PF810, it will not be enlarged to full screen.