Canon PowerShot SD990 IS User Manual page 77

You can shoot while checking the brightness distribution of your composition
in the histogram (p. 44) (real time histogram).
Set the display to [Information
Display] (p. 42).
Select [Histogram].
Press the
MENU
button, and select
[Histogram] from the
a
tab, and press
the
~ ~
buttons to select [On].
The histogram will appear and the
brightness distribution in the composition
will display in real time.
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