Horizon's user interface shows a real time camera preview and an overlayed rectangle viewport. The viewport highlights the area of the video that will be cropped and used for the resulting video. Try to rotate your device and watch how the viewport changes.
The viewport rotates and changes size, so that the resulting video has correct orientation. When the viewport is enalrged/shrunk, the resulting video zooms out/in.
The way the viewport rotates and scales depends on the mode you have selected by tapping the "Mode button":
- Flex: This is the default choice because it is best for the most regular usage scenarios. The viewport rotates and adjusts its size intelligently so that the filed of view is large and the final video smooth. The resulting video will zoom in/out smoothly.
Read more on tweaking the behaviour of Flex mode here.
- Rotate: The viewport rotates but its size remains the same. This option is ideal if you plan to rotate your device at high speeds. The resulting video does not zoom in/out, but the field of view is narrow.
- Locked: The orientation of the video is not corrected. This mode is usefull if you plan on holding your device either horizontally or vertically.
Read more on altering the "Locked" mode orinetation here.