Pentax SF1 Manual page 37

Difficult Subjects for Auto Focusing
This camera's auto-focusing system is extremely precise
and highly sophisticated, yet there are certain types of
subjects {due to their brightness, contrast, shape and
size) that make focusing very difficult. For these
situations, use the focus lock or manual focusing, or take
advantage of the built-in RTF (Retractable TTL-Auto
Flash) in dark locations.
• Extremely low-contrast subjects (little difference
between the bright and dark areas), such as a white wall.
• Extremely dark subjects.
• Extremely fast-moving subjects.
• Subjects with only horizontal lines.
• Subjects with detailed and/or complex patterns.
• Subjects positioned against harsh reflected light, strong
backlight or an extremely bright background.
• Subjects composed of elements both near and far within
the focus frame.
Accessories Not Usable in Auto Focusing
The following accessories cannot be used in the auto¬
focus mode or the FI (Focus Indication) system. Use
the matte area of the viewfinder for focusing.
• Special-effect filters, magic-image attachments or stereo
adapters.
• Linear polarizing filters because this camera has a half-
mirror. Use the circular polarizing filters.
• Extension Tubes and Auto Bellows.
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