Canon EOS REBEL XS Instruction Manual page 69

When Autofocus Falls
Autofocus can fail to achieve focus (the focus confirmation light <O>
blinks) with certain subjects such as the following:
Subjects difficult to focus
® Low-contrast subjects
Example: Blue sky, solid-color walls, etc.
® Subjects in low light
® Extremely backlit or reflective subjects
Example: Car with a reflective body, etc.
® Near and far subjects covered by an AF point
Example: Animal in a cage, etc.
® Repetitive patterns
Example: Skyscraper windows, computer keyboards, etc.
In such cases, do one of the following:
(1) With One-Shot AF, focus an object at the same distance as the
subject and lock the focus before recomposing. (p.46)
(2) Set the lens focus mode switch to <MF> and focus manually.
®, If an Extender (sold Separately) is attached and the maximum aperture Of
the lens is ft5_6 or smaller (larger f/number), AF wi!l not be possible
(except Live mode AF). For details, see the Extender's instruction
manual.
@ For the cases AF can fail to achieve focus with Live mode AF, see
page 106.
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