FujiFilm KLASSE W Owner's Manual page 46

Selecting Flash Mode
Flash-off mode
Used when photographing a subject under room
lighting or outside of a flash range such as in a
theater or a stadium.
The flash does not fire.
When taking pictures under low light, use a tripod to
avoid camera shake.
46
Fill-in Flash mode
Used when photographing a subject against
backlight such as a window or in shade like under
a tree.
Fires the flash even when the background is bright.