Canon PowerShot S2IS User Manual page 45

Turn the mode lever to the right to
set the camera to Playback mode.
The last recorded image appears on the LCD
monitor (or viewfinder).
Magnified approximately 10 times
Approximate position of the magnified area
Magnified approximately 5 times
Approximate position of the magnified area
Turn the zoom lever toward
~
to magnify the image and toward
~
to cancel the magnified
display.