When Autofocus Fails - Canon EOS 5D MARK IV Instruction Manual

When Autofocus Fails

Autofocus may fail to achieve focus (focus indicator <o> in the
viewfinder blinks) with special subjects such as the following:
Subjects Difficult to Focus
Subjects with very low contrast
(Example: Blue skies, solid-color flat surfaces, etc.)
Subjects in very low light
Strongly backlit or reflective subjects
(Example: Cars with highly reflective bodies, etc.)
Near and distant subjects framed close to an AF point
(Example: Animals in cages, etc.)
Subjects such as dots of light framed close to an AF point
(Example: Night scenes, etc.)
Subjects with repetitive patterns
(Example: Skyscraper windows, computer keyboards, etc.)
Subjects with finer patterns than an AF point
(Example: Faces or flowers as small as or smaller than an AF point,
etc.)
In such cases, focus in either of the following two ways.
(1) With One-Shot AF, focus on an object at the same distance as the
subject and lock the focus, then recompose the shot (p.101).
(2) Set the lens's focus mode switch to <MF> and focus manually
(p.159).
Depending on the subject, focus may be achieved by slightly
recomposing the shot and performing AF operation again.
For conditions that make focusing difficult with AF during Live View
shooting or movie shooting, see page 324.
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