Canon EOS REBEL T8i Advanced User's Manual page 140

Adjusting the Miniature Effect
1.
Move the AF point.
Move the AF point to the position to focus on.
2.
Move the scene frame and shoot.
Move the scene frame if the AF point is outside of it, so that the AF
point is aligned with it.
To make the scene frame movable (displayed in orange), press the
<
[
orientation. Switching scene frame orientation is also possible with the
<
keys when in vertical orientation.
Turn the <
scene frame again, press the <
To confirm the position of the scene frame, press <
> button or tap [ ] in the lower right of the screen. By tapping
], you can also switch between vertical and horizontal scene frame
> < > keys when in horizontal orientation and <
> or < > dial to move the scene frame. To center the
> button.
140
> < >
>.