When Autofocus Fails - Canon EOS Rebel XTi Instruction Manual

When Autofocus Fails.
*'~jlliiM"""""
The camera might not be able to focus the following types of subjects:
~ Low-contrast subjects
Example: Blue sky, solid-color walls, etc.
iI
Subjects in low light.
(I
Extremely backlit reflective subjects
Example: Car with a reflective body, etc.
@
Overlapping near and far objects
Example: Animal in a cage, etc.
\W
Repetitive patterns
Example: Skyscraper windows, computer keyboards, etc.
In such cases, do one of the following:
1. Focus an object at the same distance as the subject and lock the
focus before recomposing. (p.42)
2. Set the lens focus mode switch to <MF> and focus manually.
[]] If an Extender (optional) is attached and the maximum aperture of the lens
is f/5.6 or smaller (larger ffnumber), AF will not be possible. For details, see
the Extender's instruction manual.
160