Canon A650 IS - Manual (Page 88)

Shooting Using the Mode Dial 86
z The maximum shutter speed with synchronized flash is
1/500 second. Therefore, even if an aperture value is preset,
the aperture value may automatically be reset to match the
synchronized flash speed.
Aperture Value Display
z
The larger the aperture value, the smaller the lens aperture.
Safety Shift
With and modes, if [Safety Shift] is turned [On] in the Rec.
menu, the shutter speed or aperture value is automatically adjusted
for the correct exposure when it cannot be otherwise obtained.
Safety Shift is disabled when the flash is enabled.
F2.8 F3.2 F3.5 F4.0 F4.5 F4.8 F5.0 F5.6 F6.3 F7.1 F8.0