Pentax ist - Manual (Page 103)

101
B
ASIC OPERA
TION
(PREP
ARA
TION)
B
ASIC OPERA
TION
(SHOO
TING)
AD
V
ANCED OPERA
TIONS
O
THERS
Hard-to-Autofocus Subjects
The autofocus system is highly precise, but not perfect.
Depending on the brightness, contrast, shape, and size of your
subject, the autofocus system may not operate. In such a case,
set the focus mode switch to
and use the manual focus
mode to focus the lens on the subject with the aid of the matte
field in the viewfinder (see pages 94 and 95).
Subjects, which may fool the autofocus system, include:
a)Extremely low-contrast subjects such as a white wall in the
focus points .
b)Subjects which don't reflect much light in the focus points
.
c) Subjects that are moving too fast.
d)Multiple subjects in the foreground and background of the
focus points . In this case, the subject may not be in
focus even if the focus indicator is lit.
e)Subjects positioned against reflected light or strong backlight
or with extremely bright backgrounds.
f) If vertical or horizontal line patterns appear in the focus
points .
Notes on Accessories
If you use any special effect filter, Magic Image Attachment or
Stereo Adapter, autofocus and manual focus using the focus
indicator
in the viewfinder cannot be used. In this case, use
manual focus using the viewfinder's matte field. See page 95.