FujiFilm KLASSE W Owner's Manual page 31

Focus mark
With the focused composition, press the
shutter button halfway (AF Lock).
Make sure the focus mark in the viewfinder is lit.
At this time, the exposure is also locked (AE Lock).
Move the camera back to the original
composition while pressing the shutter button
halfway (AF Lock).
Press the shutter button.
The AF lock operation can be redone as needed before
releasing the shutter.
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