When Autofocus Fails - Canon EOS 70D Instruction Manual

When Autofocus Fails

Autofocus can fail to achieve focus (viewfinder's focus confirmation light
<o> blinks) with certain subjects such as the following:
Subjects Difficult to Focus
Very low-contrast subjects
(Example: Blue sky, solid-color walls, etc.)
Subjects in very low light
Extremely backlit and reflective subjects
(Example: Car with a highly 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 either of the following:
(1) With One-Shot AF, focus an object at the same distance as the
subject and lock the focus before recomposing the shot (p.75).
(2) Set the lens focus mode switch to <MF> and focus manually
(p.110).
For subjects difficult to focus during Live View shooting or movie shooting
with [u+Tracking], [FlexiZone - Multi], or [FlexiZone - Single], see page
241.
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