Panasonic Lumix S9

Metering / Exposure / ISO Sensitivity – Locking Focus and Exposure (AF/AE Lock)
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Locking Focus and Exposure (AF/AE Lock)
Lock the focus and exposure in advance to take pictures with the same
focus and exposure settings while changing the composition.
This is useful when you want to bring an edge of the screen into focus or
there is a backlight, for example.
1
Register [AE LOCK], [AF LOCK], or [AF/AE LOCK] to the
Fn button. (Fn Buttons: 488)
• These cannot be registered to [Fn3] to [Fn7].
[AE LOCK]
The exposure is locked.
[AF LOCK]
The focus is locked.
[AF/AE LOCK]
Both focus and exposure are locked.