I figured out what it does: it conforms the display to the format of the video that is being recorded (16:9 aspect) with black top & bottom. With it off, the display is filled top to bottom, cropping out the sides. On a phone with a 16:9 display, it has no effect.

Great! Thanks for passing this bit of enlightening to us... Having both a PC screen and smartphone display with 16:9 format, I now understand why I could not see a difference with the option turned on or off.

Thanks for sharing this information to our valued DJI Forum members. We do appreciate your continued support!

The Robomaster S1 could use an updated manual and better descriptions for virtually everything.