FujiFilm KLASSE W Owner's Manual page 59

Mode
The bulb mode is canceled after each shot.
Retaining/Canceling
Decide on the composition and press the
shutter button.
To avoid camera shake, use a tripod.
When the bulb time is not set.
The camera keeps the shutter open while the shutter
button is being pressed.
When the bulb time is specified
The camera opens the shutter for the time specified,
and then closes it automatically.
The bulb time displayed on the LCD decreases
with the count of each second.
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