NEC NP3151W - Manual (Page 104)

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6. Using On-Screen Menu
 Menu Descriptions & Functions [SETUP]
[BASIC]
Selecting Keystone mode [KEYSTONE]
This feature allows you to correct keystone distortion.
Selecting this item will display the Keystone setting menu.
You can correct vertical distortion manually from the menu. (
→ page 30 )
Changes will be saved even when you turn off the projector.
NOTE: The [KEYSTONE] item is not available when [CORNERSTONE] or [GEOMETRIC CORRECTION] is selected.