Canon IXUS 115 HS - Manual (Page 101)

101
You can change the metering method (brightness measuring function) to
match the shooting conditions.
Choose the metering method.
 After pressing the m button, press the
op buttons to choose , then press the
m button again.
Choose an option.
 Press the op buttons to choose an
option, then press the m button.
 The setting will appear on the screen.
Changing the Metering Method
Evaluative
For standard shooting conditions, including back lit shots.
Automatically adjusts the exposure to match the shooting
conditions.
Center
Weighted Avg. Averages the light metered from the entire frame, but gives greater
weight to the center.
Spot
Only meters within the (Spot AE Point frame) that appears at
the center of the screen.