Change the slide size
1. Select one or more slides in the slide list area.
2. Choose in the group Size, you can choose:
Scale 1:1: The image is displayed centered on screen using its original dimension (scale 1:1).
Best Fit: The image is displayed maximized on screen. The aspect ratio is preserved and the image is fully visible. The screensaver background may be visible.
Zoom: The image is displayed maximized on screen. The aspect ratio is preserved but the whole screen is used to display the image. The background is not visible and the image may be cropped.
If you specified a Margin in general tab, the image will not touch the border of the screen.