Canon PowerShot SX70 HS Digital Camera - Manual (Page 82)

Shooting with AF Lock
The focus can be locked. After you lock the focus, the focal position will not
change even when you release your finger from the shutter button.
1
Lock the focus.
z With the shutter button pressed halfway,
press the button.
z The focus is now locked, and [ ] and
the MF indicator are displayed.
2
Compose the shot and shoot.
z To unlock the focus, press the button
again, and choose [ ] or [ ].
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