In the Screen Properties dialog you can enter the parameters for size and proportion, for a number of output options and for the quality of image display data. By the way, the screen is the total area available for creation and design of your show.
In the left Media Pool section click category 
Screens and the screens will be listed on the right.
Right-click the required screen and select Properties and the dialog will appear. As an alternative you can also open this dialog as follows:
...by right-clicking the screen window and selecting Properties.
...via buttons in the Properties Dialog of Video or Live Video tracks, Picture tracks or Text tracks.
Here you enter the corresponding screen aspect ratio. You can choose an aspect ratio for particular media or define one yourself. If the aspect ratios of the pictures or videos used deviate from this entry, black bars appear on the screen.
Make sure that a correct output size is entered as it is relevant for the display layout for guide lines and multidisplay shows. Moreover, it is the reference value for the display data and when images or videos are to be displayed at their original size on the screen. (... for displaying one image pixel is turned into a display pixel). For multidisplay shows enter width and height of the entire screen for the output size. Note: If you select Keep aspect ratio it will do to enter the width, the height results from the chosen aspect ratio.
The entry for Assignment for RX setup is only relevant for multimaster mode. At Screen ID you enter the output screen for the master PCs. If several master PCs are to output to the same screen the Screen ID on all master PCs must be identical.
You can enter a default size for video creation. It is used as a basis for video output and stands for the total picture size for multidisplay presentations with split video files. If you select Keep aspect ratio it will do to enter the width, the height results from the chosen aspect ratio.
See also