FujiFilm KLASSE W Owner's Manual page 27

In some cases as described below, the camera may not be able to bring the subject into focus. In such a case,
photograph the subject with the AF lock ( P.30, 32) or in the manual-focus mode ( P.52).
When facing toward a bright light source such as sunlight or reflected light such as from a windshield or the sea
When there is a reflective surface such as a mirror or metallic surface at the center of the frame
When the background is brighter than the subject
When the contrast of the subject is extremely low
When the subject is composed of only vertical lines
When the subject is moving at high speed
Subject not suitable for AF
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