YABER Y30 Mode D'emploi page 13

Important function
<Innovative 4D Keystone Correction> there are two ways to correct the
trapezoid: "vertical" and "horizontal", you can directly use the remote
control for trapezoidal correction.
1. vertical adjustment range: -50 ~ + 50. When the vertical coefficient is
gradually increased upward, the top of the projected screen gradually
becomes smaller; When the vertical coefficient is gradually lowered, the
lower part of the projected screen gradually becomes smaller.
2. horizontal adjustment range: -50 ~ + 50, when the horizontal coeffi-
cient is gradually increased upward, the left side of the projected screen
does not change, the right side of the screen gradually remains and the
left side of the screen does not change ; When the horizontal coefficient
is gradually lowered, the left side of the screen is gradually reduced, the
right side of the screen constant.
1.1 "Vertical". Range: -50 ~ +50
If the projection image is tilted vertically, as shown in (1), press the "M"
button on the remote control, select "Trapezoidal Adjustment", then press
the "OK" button and set the vertical value to "+", until to achieve the
projection effect (2).
If the projection image is tilted vertically, as shown in (3), press the "M"
button on the remote control, select "Keystone adjustment", then press
the "OK" button and set the vertical value to "-", until to achieve the
projection effect (4).
（1）
（3）
10
（2）
（4）