Mitsubishi WS-A48 Owner's Manual page 61

Part IV: Operation
For the 4:3 Models
Note the difference between the appearance of figures in Normal Broadcast and Widescreen Picture.
Normal Broadcast Picture (4:3) Widescreen Picture - HD 1080i (16:9)
Standard
(Recommended)
F
Zoom
(Recommended for Letterbox)
Standard
(Not Recommended)
1
Expand
(Recommended for Broadcast with Black Side Bars)
Letterbox
(Recommended)