Aspect ratio
Also known as: frame ratio, 16:9, 4:3
The ratio of a video frame's width to its height, such as 16:9 for widescreen, 4:3 or 8:7 for taller action-camera modes, and 9:16 for vertical video.
Updated
What it means
Aspect ratio is the shape of the frame, written as width to height. 16:9 is the standard widescreen shape of TVs, laptops and YouTube. 4:3 is squarer, 1:1 is square, and 9:16 is the tall shape of phone screens and short-form platforms. Cinematic letterbox looks such as 2.39:1 are usually created by cropping a 16:9 frame.
Action cameras add a few of their own. Many sensors are taller than 16:9, so cameras offer 4:3 modes, and recent GoPros record 8:7, which uses nearly the whole sensor. Those taller frames are rarely meant to be watched as they are; they are raw material to crop later.
How it works in practice
Shooting 8:7 or 4:3 makes sense when you do not yet know where the video will end up. From one tall clip you can crop a 16:9 version and a 9:16 version for social without either feeling cramped. GoPro's SuperView takes the opposite route: it captures 4:3 and stretches the edges to fill 16:9 in camera, giving an immersive wide look with some distortion at the sides.
For a single widescreen edit, shooting 16:9 directly is simpler: files are smaller, nothing is wasted and what you see on the screen is what you get. Drones and phones default to 16:9 for the same reason, while 360 reframing lets you choose the ratio at export.
What to watch out for
Mixing ratios in one timeline is where most problems start. A 4:3 clip dropped into a 16:9 project either shows black bars on the sides, called pillarboxing, or gets scaled up and cropped top and bottom, which can cut off heads or the horizon you composed for. Decide on one delivery ratio and crop each clip deliberately.
Another mistake is planning to crop vertical clips out of 16:9 footage. You keep only about a third of the width, so a 1080p clip leaves a slice barely 608 pixels wide, and even 4K drops to roughly 1080p vertical. If vertical matters, shoot taller frames from the start and keep the subject near the center of the field of view.
How RawClip handles it
RawClip delivers a landscape highlight in 4K and 1080p and does not output vertical 9:16 video, so make any vertical cut for social separately. 360 clips need reframing to a flat MP4 or MOV in the Insta360 app or Insta360 Studio before upload, and that export is where you choose their shape.