How to use the video button of the Xiaomi 15 Ultra Photography Kit after connecting to the phone?

The Xiaomi 15 Ultra Photography Kit is featured with four convenient buttons, detachable shutter button, customize dial, zoom lever, and video button. Video button can make you easily use the video recording function with the combination of the Xiaomi 15 Ultra and the Xiaomi 15 Ultra Photography Kit.
When you are shooting or videoing in the Camera APP, singly press to quickly start video recording. The default function is to quickly switch to video mode and start video recording. You can also customize different features like adjusting the aspect ratio, auto exposure and more.