Adjusting Video Clip Aspect Ratio
Video clips usually come in one of two aspect ratios, 4:3 or 16:9. Depending on your media clips and the medium you will be using to view your video, you can adjust your video’s aspect ratio accordingly. Before you produce your video, set the aspect ratio for all of the video clips so that it matches the aspect ratio of your project.
Depending on the aspect ratio of your project and the aspect ratio of your clips, you have two options to choose from.
If your project aspect ratio is 4:3 and you wish to produce video with clips that have a 16:9 aspect ratio, right-click on the video clip you want to adjust and select Set Aspect Ratio.