I am using Win10 (64bit) PC and have imported 4k video from my Sony 4k camera
No issues with editing, etc but when I export it (tried several 4k formats), I have black bars all around the video content, yet the titles & transitions do take up the full height of the screen - see below.


The screenshots above were captured through the same window in the same position.
Any ideas as to how to increase the size of the video content ?